Citation
Thermoregulation in the brown water snake, Natrix taxispilota, with discussion of the ecological significance of therman preferenda in the order Squamata

Material Information

Title:
Thermoregulation in the brown water snake, Natrix taxispilota, with discussion of the ecological significance of therman preferenda in the order Squamata
Creator:
Goodman, Donald Eugene, 1944-
Publisher:
[s.n.]
Publication Date:
Language:
English
Physical Description:
ix, 85 leaves. : illus. ; 28 cm.

Subjects

Subjects / Keywords:
Acclimatization ( jstor )
Body temperature ( jstor )
Digestion ( jstor )
Ecology ( jstor )
Lizards ( jstor )
Reptiles ( jstor )
Snakes ( jstor )
Species ( jstor )
Thermoregulation ( jstor )
Water temperature ( jstor )
Animal heat ( lcsh )
Body temperature -- Regulation ( lcsh )
Dissertations, Academic -- Zoology -- UF ( lcsh )
Water-snakes ( lcsh )
Zoology thesis Ph. D ( lcsh )
Genre:
bibliography ( marcgt )
non-fiction ( marcgt )

Notes

Thesis:
Thesis - University of Florida.
Bibliography:
Bibliography: leaves 80-84.
General Note:
Manuscript.
General Note:
Vita.

Record Information

Source Institution:
University of Florida
Holding Location:
University of Florida
Rights Management:
Copyright [name of dissertation author]. Permission granted to the University of Florida to digitize, archive and distribute this item for non-profit research and educational purposes. Any reuse of this item in excess of fair use or other copyright exemptions requires permission of the copyright holder.
Resource Identifier:
000985816 ( ALEPH )
17625022 ( OCLC )
AEW2229 ( NOTIS )
AA00004938_00001 ( sobekcm )

Downloads

This item has the following downloads:

thermoregulation00good.pdf

thermoregulation00good_0083.txt

thermoregulation00good_0013.txt

thermoregulation00good_0011.txt

thermoregulation00good_0057.txt

thermoregulation00good_0070.txt

thermoregulation00good_0033.txt

thermoregulation00good_0014.txt

thermoregulation00good_0065.txt

thermoregulation00good_0006.txt

thermoregulation00good_0073.txt

AA00004938_00001_pdf.txt

thermoregulation00good_0080.txt

thermoregulation00good_0036.txt

thermoregulation00good_0018.txt

thermoregulation00good_pdf.txt

thermoregulation00good_0000.txt

thermoregulation00good_0068.txt

thermoregulation00good_0008.txt

thermoregulation00good_0044.txt

thermoregulation00good_0076.txt

thermoregulation00good_0042.txt

thermoregulation00good_0016.txt

thermoregulation00good_0054.txt

thermoregulation00good_0010.txt

thermoregulation00good_0084.txt

thermoregulation00good_0039.txt

thermoregulation00good_0049.txt

thermoregulation00good_0087.txt

thermoregulation00good_0017.txt

thermoregulation00good_0028.txt

thermoregulation00good_0056.txt

thermoregulation00good_0061.txt

thermoregulation00good_0067.txt

thermoregulation00good_0064.txt

thermoregulation00good_0093.txt

thermoregulation00good_0096.txt

thermoregulation00good_0085.txt

thermoregulation00good_0074.txt

thermoregulation00good_0002.txt

thermoregulation00good_0051.txt

thermoregulation00good_0021.txt

thermoregulation00good_0088.txt

thermoregulation00good_0034.txt

thermoregulation00good_0097.txt

thermoregulation00good_0046.txt

thermoregulation00good_0053.txt

thermoregulation00good_0059.txt

thermoregulation00good_0040.txt

thermoregulation00good_0030.txt

thermoregulation00good_0038.txt

thermoregulation00good_0032.txt

thermoregulation00good_0009.txt

thermoregulation00good_0060.txt

thermoregulation00good_0091.txt

thermoregulation00good_0023.txt

thermoregulation00good_0050.txt

thermoregulation00good_0024.txt

thermoregulation00good_0005.txt

thermoregulation00good_0058.txt

thermoregulation00good_0007.txt

thermoregulation00good_0075.txt

thermoregulation00good_0037.txt

thermoregulation00good_0052.txt

AA00004938_00001.pdf

thermoregulation00good_0001.txt

thermoregulation00good_0043.txt

thermoregulation00good_0081.txt

thermoregulation00good_0047.txt

thermoregulation00good_0055.txt

thermoregulation00good_0019.txt

thermoregulation00good_0062.txt

thermoregulation00good_0031.txt

thermoregulation00good_0095.txt

thermoregulation00good_0004.txt

thermoregulation00good_0094.txt

thermoregulation00good_0069.txt

thermoregulation00good_0012.txt

thermoregulation00good_0041.txt

thermoregulation00good_0079.txt

thermoregulation00good_0020.txt

thermoregulation00good_0072.txt

thermoregulation00good_0066.txt

thermoregulation00good_0092.txt

thermoregulation00good_0078.txt

thermoregulation00good_0022.txt

thermoregulation00good_0027.txt

thermoregulation00good_0077.txt

thermoregulation00good_0082.txt

thermoregulation00good_0089.txt

thermoregulation00good_0063.txt

thermoregulation00good_0015.txt

thermoregulation00good_0071.txt

thermoregulation00good_0029.txt

thermoregulation00good_0035.txt

thermoregulation00good_0045.txt

thermoregulation00good_0025.txt

thermoregulation00good_0048.txt

thermoregulation00good_0003.txt

thermoregulation00good_0086.txt

thermoregulation00good_0026.txt

thermoregulation00good_0090.txt


Full Text














Thermoregulation in the Brown Water Snake, Natrix taxispilota,
with Discussion of the Ecological Significance of
Thermal Preferenda in the Order Squamata














By

DONALD EUGENE GOODMAN


A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA IN PARTIAL
FULFILLMENT OF '[liE REQUIREMENTS FOR THE DEG'E-E OF
DOCTOR OF PHILOSOPHY









UNIVERSITY OF FLORIDA
1971




Thermoregulation in the Brown Water Snake, Natrix taxispilota,
with Discussion of the Ecological Significance of
Thermal Preferencia in the Order Squamata
By
DONALD EUGENE GOODMAN
A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
HIE UNIVERSITY OF FLORIDA IN PARTIAL
FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1971


This work is dedicated to my parents, Arvil E, Goodman and
Clara Metcalf Goodman, who encouraged my pursuit of biology in
general and snakes in particular.


ACKNOWLEDGEMENTS
I gratefully acknowledge the help of the many individuals who
contributed to this study. I especially thank Drs. Archie F. Carr,
Brian K. McNab, Frank G. Nordlie, and E. S. Ford for their assistance
in procurement of equipment, and invaluable comments on the manuscript.
I thank Dr. Paul Byvoet and Mr. Ralph Carroll for their technical aid.
I am indebted to Ms. Debbie Bee, Ms. Marion Edwards, Ms. Martha
Johnston and Mr. Craig Parenteau for aid in data collection and to
Mr. Porter Reed for helping me reclaim my experimental pen from the
depths of Lake Alice after heavy rains.
I also thank Ms. Jill Jordan for proofreading the manuscript,
assistance in drawing figures, collection of data, and mind-boggling
assessments of my data. I profited from the useful counsel of Ms. Peg
Estey in the preparation of illustrative material.
Finally, my thanks to Ms. Donna Gillis for typing this manuscript
and for removing many of the bureaucratic barricades to completion of
my degree.
iii


TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS iii
LIST OF TABLES vi
LIST OF FIGURES vii
ABSTRACT ix
INTRODUCTION 1
MATERIALS AND METHODS 3
Collection and Maintenance of Specimens 3
Radio Telemetry 4
Experimental Apparatus 4
Thermal Gradient 13
Metabolism 14
Digestive Efficiency 15
RESULTS AND DISCUSSION 17
Preferred Body Temperature 17
Behavioral Thermoregulation 30
Morning Emergence 30
Effect of air and water temperatures 30
Effect of acclimation 38
Effect of physiological state 41
Effect of light 41
Temporal changes in emergence response 44
Maintenance of Preferred Body Temperature 45
Evening Submergence 47
iv


Factors Affecting Preferred Body Temperature 52
Digestion 53
Other Factors 59
Ecological Significance of Reptilian PBT 62
SUMMARY 78
LIST OF REFERENCES 80
BIOGRAPHICAL SKETCH 85
v


LIST OF TABLES
Table Page
1 The preferred ranges of body temperature of freshly
caught Natrix taxispilota 26
2 Effect of digestion on normal range of preferred
body temperatures 58
3 Data for points plotted in Figure 19 for primary
heliothermic lizards 69
4 Data for points plotted in Figure 21 for nocturnal
reptiles 75
5 Data for points plotted in Figure 21 for diurnal
snakes and forest lizards
76


LIST OF FIGURES
Figure Page
1 X-ray photograph of a Natrix taxispilota with an
ingestible radio transmitter in its stomach 6
2 Experimental pen at Lake Alice ...... 9
3 Experimental chamber used to determine the responses
of water snakes to various combinations of air and
water temperature 12
4 Effect of acclimation temperature on the range of body
temperatures selected by Natrix taxispilota in a
gradient ^9
5 Natrix taxispilota body temperatures and associated
air temperatures at Neman's Lake during December
and January 21
6 Natrix taxispilota body temperatures and associated
air temperatures at Newnan's Lake during March .... 22
7 Body temperature of Natrix taxispilota collected at
Newnan's Lake between 1130 and 1600 hours from March
through October 25
8 Metabolic rate of Natrix taxispilota as a function of
acclimation temperature and body weight ....... 29
9 Behavioral responses of a 554 g Natrix taxispilota to
combinations of air and water temperature from 5C
through 35C 31
10 Body temperatures of Natrix taxispilota and associated
air temperatures at time of capture at Newnan's
Lake 35
11 Average body-air temperature differentials of Natrix
taxispilota at Newnan's Lake as a function of air
temperature 37
12 Number of Natrix taxispilota basking on various days
throughout the year 40
13 Number of Natrix taxispilota basking at various
times on April 9, 1970 43
vii


14 The relationship between body size and body-air
temperature differentials of Natrix taxispilota ... 49
15 Changes in body temperature of a Natrix taxispilota
thermoregulating under natural climatic
conditions 51
16 Four-day body temperature record of a Natrix
taxispilota digesting a fish 55
17 The effect of temperature on digestive extraction
efficiency of Natrix taxispilota 57
18 The relationship between preferred body temperature
and critical thermal maximum in reptiles 65
19 Relationship between preferred body temperature of
primary heliotherms and the highest air temperature
recorded in their collection area 68
20 Effect of temperature on the metabolic rate of a 509 g
Natrix taxispilota 72
21Relationship between reptilian preferred body temperature
and highest air temperature recorded in their collection
area 74
viii


Abstract of Dissertation Presented to the Graduate Council
of the University of Florida in Partial Fulfillment of
the Requirements for the Degree of Doctor of Philosophy
THERMOREGULATION IN THE BROWN WATER SNAKE, NATRIX TAXISPILOTA,
WITH DISCUSSION OF THE ECOLOGICAL SIGNIFICANCE OF
THERMAL PREFERENDA IN THE ORDER SQUAMATA
By
Donald Eugene Goodman
June, 1971
Chairman: Dr. A. F. Carr, Jr.
Co-Chairman: Dr. B. K. McNab
Major Department: Zoology
Thermoregulatory behavior of the brown water snake, Natrix taxispilota,
was studied under natural and laboratory conditions. During daylight hours,snak
move among shade, sun, and water to maintain their preferred body tempera
ture. In the evening they submerge regardless of air-water temperature
differential and spend the night in the water. There are minimal thermal
thresholds for morning emergence and these levels are affected by thermal
acclimation and physiological state of the animal.
The preferred range of body temperatures of this species decreases
with increasing acclimation temperature. When digesting food, snakes
thermoregulate within a sub-range of the normal preferred range and
digestive extraction efficiency is greatest at this level -- about 30C.
It is suggested that high thermal extremes are selective forces which
directly fix the critical thermal maximum of reptiles and indirectly fix
the preferred body temperature. The relatively low thermal preferenda of
snakes may be a function of their lack of limbs which precludes thermo
regulation with the degree of independence of conductive heat exchange with
the substrate characteristic of lizards.


INTRODUCTION
Many species of reptiles utilize solar radiation to attain body
temperatures greatly in excess of ambient temperatures. Some species
have an extensive behavioral repertoire which enables them to regulate
their body temperature within fairly narrow limits. Since these initial
discoveries were reported (Cowles and Bogert, 1944), scores of papers
have appeared documenting such behavior for other reptilian species,
and it now seems obvious that thermoregulation is a general feature of
reptilian behavior. While some reptiles possess physiological mechanisms
that contribute to thermal homeostasis (Lueth, 1941; Cole, 1943; Cowles,
1958; Ruibal, 1961; Bartholomew and Tucker, 1963; Heath, 1965;
Hutchison ej: al., 1966; Kour and Hutchison, 1970; Weathers, 1970),
it is behavioral utilization, directly or indirectly, of solar
radiation that permits the attainment of high preferred thermal levels.
The contribution of metabolic heat to maintenance of thermal homeostasis
is negligible (Lueth, 1941; Cole, 1943; Mackay, 1964; Schmidt-Nielsen
and Dawson, 1964; Brattstrom, 1965) even in large reptiles.
With few exceptions, these studies have dealt with lizards, and
very little information exists for other reptilian groups. The few
studies of thermoregulation involving snakes (Cowles and Bogert, 1944;
Carpenter, 1956; Fitch, 1956, 1965; Brattstrom, 1965; Stewart, 1965;
Myres and Eells, 1968; Kitchell, 1969; McGinnis and Moore, 1969;
Osgood, 1970) indicate that snakes differ from lizards in their thermal
behavior. They seem to have lower thermal preferenda and to regulate
less precisely. Some workers (Cowles and Bogert, 1944; Schmidt-Nielsen
1


2
and Dawson, 1964) believe these differences are correlated with differences
in the ecology of the two groups. Most snakes, for instance, are nocturnal
or crepuscular and many are fossorial; lizards are mostly diurnally active
and terrestrial. Even among nocturnal and fossorial reptiles, however,
basking in the sun has been either regularly or occasionally reported
(Cowles and Bogert, 1944; Bailey, 1949; Brattstrom, 1952). The signi
ficance of diurnal thermoregulation in such forms has never been explored.
This study was undertaken to determine the significance of thermo
regulation in a species of snake which is both semi-aquatic and
nocturnally active. Natrix taxispilota, the brown water snake,spends
nights in the water of large open lakes or rivers and springs. During
the daylight hours of the wanner months, the species commonly lies on
limbs overhanging the water, either in the sun or in the shade. Except
for reproductive behavior in the early spring, little activity occurs
during the day. This snake almost never occurs away from the water's
edge, and the aerial phase of its existence is limited to basking on
vegetation, rather than shore. While lying above the water, the snake
is surrounded by a thermal medium that is virtually homogeneous, and
heat exchange is largely radiative. Convective heat exchange there
is minimal because snakes remain in the water on windy days. Heat
exchange during the aquatic stage of the activity cycle, however,is
almost completely conductive. Because the species' activity is
partitioned almost completely between these two phases -- nocturnal
aquatic activity and diurnal arboreal basking -- it seems an ideal
snake for a study of the mechanisms and significance of thermo
regulation.


MATERIALS AND METHODS
Collection and Maintenance of Specimens
Almost all the snakes used for this study were collected at
Newnan's Lake, 8.7 km east of Gainesville, Alachua County, Florida.
This 2390 hectare lake has a mean depth of two m and is bordered by
trees, particularly pond cypress Taxodium ascendensand water ash
Fraxinus caroliniana, both of which extend from the shoreline out for
as much as 20 m into the lake. It is at the interface of the lake
and the outermost trees that most of the Matrix taxispilota were found
basking. Animals used in laboratory studies were collected by hand
from a motorboat. Cloacal temperature was recorded at this time with
either a Schultheis thermometer or the thermister probe of a YSI
six-channel tele-thermometer. Air temperature was taken in the shade
at the time of capture and water temperature was recorded at the surface
and at a depth of 2/3 m. A black-bulb temperature was recorded in direct
sunlight with a mercury thermometer, the bulb of which had been coated
with flat black paint.
A 1.12 km section of shoreline was used as a census area and, at
irregular intervals, the number of snakes basking in the trees of this
area was recorded. These surveys were always conducted between 1300 and
1500 hours EST. On a few days, censuses for this and other areas were
taken at hourly intervals betx^een 0700 and 1830 hours EST to determine
the extent of temporal variation in the number of basking individuals.
Associated air, water, and black-bulb temperatures were recorded during
censusing, and general weather conditions were noted.
3


4
Snakes used for thermal gradient, digestive efficiency, and metabolic
experiments were acclimated prior to use. Each animal was housed in a
plastic storage container with holes in the removable lid. These containers
were placed in a Jewett environmental cabinet, a Forma model 13 incubator,
or a Lab Line controlled environmental room where the temperature was main
tained within .5C. All snakes received 12 hours of light daily (0900-
2100 hours EST) and had water continuously available in dishes which were
too small to permit submergence of snakes weighing more than 100 g.
Radio Telemetry
Ingestible blocking oscillator radio transmitters were used to
obtain snake body temperatures under experimental conditions. The
broadcast frequency used was low enough (500-1000 kc) to permit the re
ception of both aerial and underwater signals generated within 2 m of
the receiver, an AM-FM portable radio. Antennal loops were always
necessary tu relay the signal to the receiver.
Each cylindrical (radius =7.5 mm, length = 57 mm) transmitter was
powered by a replaceable 1.5 volt silver oxide hearing aid battery and
was waterproofed with a thin coat of 1:1 mixture of beeswax and
paraffin. The transmitter was lubricated, forced into the throat of
the snake and massaged by hand to the stomach (Fig. 1). The transmitter
was regurgitated in four or more days depending on temperature. Trans
mitters were calibrated immediately before and after use.
Experimental Apparatus
To study the fluctuations of body temperatures with changing
environmental temperatures, an experimental pen was built at another
nearby location, Lake Alice. This 24-hectare lake is located on the
University of Florida campus. The pen consisted of a circular galvanized -
steel cattle watering trough 2.44 m in diameter and 61 cm high. Concrete


Figure 1.
X-ray photograph of a Natrix taxispilota with
an ingestible radio transmitter in its stomach.




7
blocks were stacked in the center of the trough to a level of about 50 cm
and a wooden cable spool 76 cm in diameter was placed on its side atop
the blocks. An antennal loop system was installed so that radio trans
mitter signals could be monitored at a distance from the pen. This
consisted of a 25-m section of insulated copper cable ringing the
pen in three perpendicular planes. Two loops, therefore, passed under
and over the spool and their components extending above the rim of the
pen were supported by arched sections of screen moulding (Fig. 2); the
third loop was situated along the inside periphery at the rim. The
ends of this antennal loop were connected to a 20-m section of insulated
copper wire which was connected by insulated tip plugs to the antenna
of a portable AM-1T1 radio. Signals generated anywhere inside the loop
could thus be monitored many meters away. A 1/4-inch mesh hardware
cloth retaining fence was attached to the top edge of the trough and
directed inward toward the center of the pen to prevent the escape of
snakes. This apparatus was floated into the lake and filled with water
to the level of the bottom of the wooden spool. The free-floating pen
was then anchored and the wire connecting the antennal loop to the
radio was sunk to the bottom between the pen and the shore. Snakes
used in this phase of research were introduced into the pen and allowed
several days to adjust to their environment. They were then force-fed
an ingestible transmitter. On sunny days, the snake had both sunny
and shaded basking sites available on the wooden spool, or it could
remain underwater in the cavities of the concrete blocks. Air, water,
and black-bulb temperatures were monitored with either a YSI tele
thermometer located on shore or with mercury bulb thermometers. In
trial determinations, the water temperature inside and outside the pen
never differed by more than 1.5C. The water inside was sometimes


Figure 2.
Experimental pen at Lake Alice.


9


10
slightly cooler, presumably because of the shade provided by the vertical
sides of the pen. Observations were made from the shore either with the
naked eye or through 30 X binoculars, depending upon the distance
separating the observer and the pen.
A laboratory apparatus was used to study thermoregulatory behavior
under more controlled conditions. A 230 liter aquarium was made by
sealing a refrigerator liner, cutting a large window in one side and
sealing in a section of reinforced glass. Water temperature was con
trolled by circulating water between the aquarium and a Forma constant
temperature water bath. A bottomless wood-frame 1/4-inch mesh cage
(90 cm X 70 cm X 40 cm) with sliding glass panels in front, was placed
above the aquarium, and Sambucus limbs were wired into positions both
underwater and above water to provide the snakes with numerous resting
and basking sites. A 250 watt infrared heat lamp was placed directly
above the right side of the cage about 20 cm above the highest basking
site. A wooden partition was hung from the top of the cage; this did
not restrict movement but rather shaded the left side of the cage from
"sunlight" (Fig. 3). Caged animals could thus either remain submerged
or bask aerially in the "sun" or shade. This aquarium-cage-water bath
combination was placed inside a Lab Line controlled environmental room
which maintains temperatures between -20 and 70C within .5C. Water,
air and black-bulb temperatures were monitored with a YSI tele-thermometer
placed outside the room. The probes were placed inside the aquarium pen
in the water, shaded air and approximately 20 cm directly below the
sunlamp respectively. The black-bulb probe was coated with flat black
paint. Ingestible transmitters were used to monitor body temperatures.
A three-plane antennal loop was placed in the aquarium cage and leads
were extended outside the room to the antenna of an AM-FM radio. All


Figure 3.
Experimental chamber used to determine the
responses of water snakes to various combinations
of air and water temperature.


12


observations were made through two 10 cm X 6 cm holes in a sheet of
brown paper which covered the glass door of the environmental room.
With this apparatus, air and water temperatures could be monitored and
varied independently, the snake's behavioral adjustments could be
observed and its body temperature recorded without disturbing the
animal.
Responses of the animals were recorded for all combinations of
air and water temperatures from 5 through 35C. A timer was attached to
the environmental room and a 12-hour light cycle (0900-2100 hours EST)
was used throughout. Because of the nature of the transmitter used,
it was difficult to separate two signals; consequently one animal,
a 554 g female, was used for all determinations. Numerous individuals
were later run at selected temperature combinations to verify the
generality of responses of this individual. The female used in this
experiment was not acclimated to any particular temperature because
reacclimation after each run would have prolonged the experiment by
many months. Also, the temperature combination changes were never
drastic. Usually the water temperature remained constant while all
air temperatures from 5C through 35C were run. Each combination was
run for two hours and then the air temperature was elevated 2C. Since
these temperature changes were gradual, there is no reason to believe
that the snakes used in this experiment were acclimated to temperatures
to which they would not ordinarily be acclimated under the same thermal
conditions in the wild.
Thermal Gradient
A thermal gradient was used to determine preferred body temperature
levels in this species. The gradient consisted of a rectangular open-
top wooden box 3.35 mm long, 30 cm wide and 30 cm high with a nickle-steel


14
alloy floor. The front of the box was marked at 5 cm intervals from the
hot to the cool end. At the cool end, a bottomless one-gallon aluminum can
was cemented to the floor of the gradient and filled 2/3 full of x^ater.
Cold water was then circulated through a coiled section of copper tubing
in the can. Heat was provided at the other end by an electric iron that
was placed flat on the metal floor. A 500 ml beaker of water was placed
beside the iron to maintain a high humidity inside the gradient. Panes
of glass were placed on top of the gradient to prevent escape of snakes
and to permit observation. A gradient with an average AT of 1C per
30 cm between 20 and 34C could be maintained indefinitely after an
initial eight hour warm-up period. Acclimated snakes were force-fed
ingestible transmitters at about 2100 hours, placed in the gradient,
and left overnight for adjustment. Body temperature and location in
the gradient were recorded at approximately 1-1/2 hour intervals between
0900 and 2400 hours of the following day. Snakes in the gradient re
ceived the same 12 hour photoperiod from overhead lighting as in their
acclimation quarters. A red light was used when readings were taken
during hours of darkness.
Metabolism
Metabolic rates were measured with a Beckman G-2 oxygen analyzer.
Metabolic chambers consisted of 21.5 cm diameter glass battery jars
30.5 cm high, with holes drilled at low and high levels on the sides
to let air in and out. A plexiglass lid with a 9.0 cm diameter hole
for a size 15 rubber stopper was cemented to the top of the chamber.
Acclimated snakes were introduced .into the chamber which was then
submerged in a controlled-temperature water-bath that maintained water
temperature within .5C. Air xras pumped through a coil of copper
tubing that was submerged in the water bath before entering the chamber.


15
Oxygen consumption readings were taken at half-hour intervals until
stable values were obtained.
Digestive Efficiency
The effect of temperature upon digestive efficiency was measured
calorimetrically. A lirge number of gizzard shad, Dorosoma cepedianum,
were collected by rotenone poisoning at Neman's Lake, and immediately
frozen. In feeding experiments, fish were weighed, ground whole in a
Waring blender and freeze-dried in a Virtis freeze-drying apparatus.
The resulting mixture was ground again and filtered through 1/4-inch
mesh screening to remove scales and large scale fragments. The re
sulting powder was thoroughly mixed and a .5 to 1.0 g sample removed
for calorimetric determination in a Parr adiabatic oxygen bomb calori
meter. The remaining powder was rehydrated to the original wet weight
calorimetric value and immediately fed to preweighed acclimated snakes
at a level of .1 g per g of body weight. The food was massaged by
hand to the snake1s stomach and animals were then replaced in acclimation
quarters and permitted to digest the meal at the temperature to which
they were acclimated.
Cages were checked daily for defecation and the feces were rinsed
out of the cages, collected in individual beakers and refrigerated.
After digestion was completed (the cessation of defecation) the
accumulated feces were either freeze-dried or vacuum dessicated and
the dry feces weighed and bombed. At the temperatures of 20C and
above, snakes passed musk from the musk glands, the amount increasing
with temperature. The quantity of musk per g of body weight was
determined at the acclimation temperatures used and samples were
bombed to determine calorimetric value. A correction for this factor
was introduced into the calculations. Digestive efficiency is defined


16
here as:
Cf On
E = 1 Ci
where E = digestive efficiency; Cf = caloric value of feces; =
caloric value of ingested food; and = caloric value of musk. Dried
samples of fish, feces, and musk were weighed to the nearest .0001
gram on a Mettler H15 balance.


RESULTS AND DISCUSSION
Preferred Body Temperature
Throughout this discussion, the term preferred body temperature
(abbreviated PBT) will be used in accordance with Peters (1964) who
defined it as "that temperature at or about which all members of a
reptilian species will maintain themselves given the opportunity to
select proper substrate, exposure to sunlight, or other thermal factors."
The PBT can thus refer to a thermal range, as initially defined (Cowles
and Bogert, 1944) or to the mean of that range, the latter being more
useful for comparisons of interspecific preferences.
The level of body temperature selected by Natrix taxispilota in a
thermal gradient is inversely proportional to the temperature at which
the snakes were acclimated (Fig. 4). This is consistent with the find
ings of Wilhoft and Anderson (1960) for Sceloporus occidentalis. The
ecological significance of such interdependence is not immediately clear.
It might be expected that PBT would be independent of acclimation as
Licht (1968) found in Anolis, and serve as an immutable focal point for
thermoregulatory behavior. In other vertebrate poikilotherms, similarly
disparate results have been obtained. Rana pipiens tadpoles (Lucas and
Reynolds, 1967) and many fish (Norris, 1963; Fry, 1964) show changes in
PBT with acclimation, but the preferred thermal level of the newt
Tari.cha rivularis cannot be shifted by acclimation (Licht and Brown,
1967). Thus, it is impossible to generalize about the capacity of
vertebrate poikilotherms for adjustment of their thermal preferenda.
17


Figure 4.
Effect of acclimation temperature on the
range of body temperatures selected by
Natrix taxispilota in a gradient.




20
Especially puzzling is the fact that the relationship in Natrix
taxispilota is inverse, because the critical thermal maximum is directly
correlated with the acclimation temperature (Lowe and Vance, 1955; Larson,
1961; Bradshaw, 1965; Kour and Hutchison, 1970) and PBT, at least in
interspecific comparisons, is directly proportional to critical thermal
maximum (Brattstrom, 1965; see Fig. 18). These inconsistencies warrant
an examination of the ecological significance of the physiological capacity
for thermal acclimation in these snakes.
Hiere is some evidence that seasonal acclimation of PBT does occur
in temperate zone reptiles. Mueller (1969) found that both PBT (measured
in a gradient) and critical thermal maximum were higher in Sceloporus
graciosus collected in the summer than in those collected in the spring.
Similar increases in the level of field body temperatures from spring to
summer have been found in two garter snakes, Thamnophis sirtalis and T.
butleri (Carpenter, 1956), and in two lizards, Cnemidophorus sexlineatus
and Sceloporus woodi (Bogert, 1949). A similar seasonal variation was
found in body temperatures of Natrix taxispilota, but the differences
were not consistent with the laboratory evidence for the relationship
between acclimation temperature and PBT. The level of body temperature
in December and early January ranged between 14 and 20C and most values
were below air temperatures (Fig. 5). By late January, higher air
temperatures resulted in body temperatures of 22.5 to 26C with values
approximating air temperature. In March, most body temperatures ranged
between 26 and 30C (Fig. 6) and exceeded air temperature. These
observations were made on sunny and relatively windless days when black-
bulb temperatures exceeded air temperatures by 4 to 10C. The occurrence
of snake body temperatures below air temperature can be explained only
as resulting from recent emergence from cooler water and initial evaporative


21
Figure 5. Natrix taxispilota body temperatures and
associated air temperatures at Neman's
Lake during (A) late December and early
January and (B) late January.


22
AIR TEMPERATURE (C)
Figure 6. Matrix taxispilota body temperatures and
associated air temperatures at Newnan's
Lake during March.


23
cooling. Throughout the warmer months, body temperatures remained
approximately within the range found in March (Fig. 7), but by mid-
October, lower air temperatures again caused a decrease in the field
body temperatures. Thus, field data provided no evidence of the inverse
relationship that might be expected between seasonal temperature (and
presumably thermal acclimation of PBT) and level of body temperature.
However, these field values for winter represent, at best, levels
of temperature attainable and not necessarily those preferred. Snakes
collected in January selected warmer temperatures in a gradient than those
collected in April or July (Table 1), suggesting that acclimation of
PBT does occur in nature. The body temperatures selected by snakes
collected in April and July did not differ significantly, indicating
that these snakes were acclimated to a common thermal level, their PBT.
During the colder weather of January, however, thermoregulatory behavior
ceased and the snakes became acclimated to the colder thermal regime of
the water in which they remained torpid. Their PBT at this time re
flected this acclimation.
Metabolic data also suggest this relationship. Figure 8 gives
the metabolic rate of snakes as a function of size and acclimation
temperature. The level of metabolism at a given temperature is in
versely correlated with acclimation temperature. This relationship has
been reported for fish, amphibians, reptiles and many invertebrates (for
extensive reviews, see Berg, 1953; Bullock, 1955; Fry, 1958) and appears
to be a nearly universal characteristic of poikilotherms. When snakes
were maintained at varying thermal regimes (30C from 0901 hours
through 2100 hours, 20C from 2101 hours through 0900 hours), however,
their metabolism became acclimated to the higher of the two temperatures
(Fig. 8). Acclimation to the highest of varying temperatures has been


Figure 7.
Body temperatures of Matrix taxispilota
collected at Newnan's Lake between 1130-
1600 hours from March through October.


NUMBER OF RECORDS
22 24 26 28 30 32
TEMPERATURE (C)
34


26
Table 1. The preferred ranges of body temperature of
freshly caught Natrix taxispilota.
JANUARY
APRIL
JULY
PBT RANGE (C)
29.4-33.5
25.3-30.9
25.2-31.1
MEAN
31.6*
27.9
28.2
N (OBS.)
3 (37)
3 (38)
4 (47)
Differences between means for April and July are not
statistically significant but the mean for January
differs significantly (p- 0.05) from the other means.


27
reported for Rana pipiens (Hutchison and Ferranca, 1970) and for several
species of fish in both the field (Brett, 1944) and under controlled
conditions (Fry et al., 1946; Heath, 1963). These data suggest that a
poikilothermal animal can acclimate the level of its metabolism by
thermoregulatory behavior. Only when the environmental temperature
becomes too cold to permit thermoregulation at the preferred level
would there occur acclimation of body functions to a non-PBT level.
There is, then, a seasonal variation in PBT of Natrix taxispilota.
It appears that the level at which body temperature is maintained sets
the acclimation temperature, and the level of thermal acclimation in
turn affects the PBT. The range of body temperatures found in Natrix
taxispilota during March through October (23-32C) correlates almost
exactly with those preferred (23.9-33.1C) by snakes acclimated to
25C and 30C -- a close agreement between field and laboratory data.
Thermoregulacion at the preferred level apparently fixes the level
of thermal acclimation throughout those parts of the year.when adequate
thermal opportunities exist. During the colder months, when this is
not possible (Fig. 5), the level of body temperature, and presumably
thermal acclimation, varies with water temperature.
The inverse relationship between acclimation temperature and
PBT probably represents an overcompensation mechanism which is of
value during periods of thermal extremes. It is unlikely that cold-
acclimated snakes in nature could ever attain the body temperatures
selected by cold-acclimated individuals in a gradient. But by be-
haviorally thermoregulating in such a manner as to attain these high
levels, snakes may significantly elevate their body temperatures.
The lower levels preferred by warm-acclimated snakes probably reflect
a mechanism that is of importance only in an evolutionary sense. The


Figure 8.
Metabolic rate of Matrix taxispilota as a
function of acclimation temperature and
body weight.
A. acclimated to 20C, B. 25C, C. 30C,
D. 35 C, E. varying temperatures (20C
night, 30C day).


LOG METABOLiSM (ccC^/hr)
29
LOG BODY WEIGHT (g)


30
highest air temperature recorded in Gainesville in a 40 year period
(Kincer, 1941) is 39.4C which is several degrees below the probable
critical thermal maximum for Natrix taxispilota (Brattstrom, 1965).
Only when drastic climatic warming occurs would snakes become acclimated
to temperatures significantly above their preferred range and there
would be a clear selective pressure favoring individuals who behavior-
ally sought cool body temperatures even if the lowest attainable body
temperature was above the preferred level.
Behavioral Thermoregulation
t
Morning Emergence
*
Brown water snakes almost invariably spend the night in the water.
Hie time of emergence depends upon several climatic factors and upon
some endogenous responses of the snake.
The effect of air and water temperatures on emergence
Figure 9 shows the response of a 554 g female water snake main
tained in the environmental chamber to all combinations of air and water
temperatures between 5 and 35C. This includes all the thermal regimes
which the species ever encounters in nature and several artificial situ
ations. The responses of several other animals to a number of these
thermal combinations never differed appreciably from those of the
554 g female so the pattern shown in Figure 9 may therefore be con
sidered representative. It should be remembered throughout the
discussion that animals used in this laboratory experiment were adapted
to the approximate thermal combinations to which their responses were
recorded (see Materials and Methods).
The lowest air temperature that elicited emergence was 16C and
then only if the water temperature was 21C or above. This latter
combination is an artificial situation at one extreme of a general


31
Figure 9. Behavioral responses of a 554 g Natrix taxispilota
to combinations of air and water temperature from
5C through 35C.
snake
snake
ke
in water
in sun
in shade


32
pattern; the colder the water temperature, the warmer the air
temperature needed to elicit emergence. The lowest water temperature
at which snakes emerged was 10C and then only if air temperature
was at least 25C (again an artificial situation). There are,
therefore, lower limits for air and water temperatures that
elicit emergence in Natrix taxispilota and above these extremes,
these minimal values are inversely related. This inverse relation
ship is not isothermal -- i.e. the slope of this air-water temperature
interface is not -1.0.
At a water temperature of 18C, snakes will emerge for a minimal
air temperature of 18C, but at water temperatures below this level
air temperatures must exceed water temperature to evoke emergence
(Fig. 9). The lower the water temperature, the greater the air-water
temperature differential required for emergence. Values for this
differential at or near the water temperature asymptote of 10C are,
as mentioned, not ecologically significant because such differentials
do not occur in nature.
At water temperatures above the air-water isothermal emergence
point (18C), the minimal water temperatures that evoked emergence
were in excess of air temperature. The higher the water temperature,
from which a snake emerges, the higher its body temperature at
emergence and the less time it takes a basking individual to reach
the preferred thermal level. This may explain why snakes emerge
from warm water into cooler air at water temperature above 18C.
Although the water is relatively warm, it is still below the preferred
level. Basking permits attainment of PBT, or at least a closer
approximation than is represented by the water temperature. Thus,
snakes apparently will not emerge when their body temperatures are


33
below 18C unless the aerial phase insures rapid attainment of this
level.
Figure 10 summarizes the field relationship between air and
body temperature. It is significant that only 5 percent of the body
temperature records are below 18C, a close agreement with laboratory
results. The decrease in number of records for snake body temperature
at air temperatures below 18C is precipitous and not a gradual attenu
ation. The body-air differentials maintained by snakes at air
temperatures from 18C through 30C are inversely correlated with
air temperature (Fig. 11). This is clearly a reflection of differential
utilization of sunlight as a function of environmental temperatures.
It is ecologically significant that there exists a lower thermal
threshold for thermophilic responses as evidenced by the refusal of
snakes to emerge at water (and therefore body) temperatures below
10C even when air temperature was warmer. Below the body temperature
required for coordinated locomotion, emergent snakes would be very
vulnerable to predation by homoiotherms. Also, at temperatures below
the threshholds for feeding and digestion, thermophilic responses
would increase the metabolic maintenance cost without providing
additional energy sources. This would deplete the reptile's energy
stores needed for periods of torpor and (at higher latitudes) hiber
nation .
When the water temperature approached the lower limit of the
preferred range (25C), a common occurrence between April and October,
the minimal air temperature required to evoke emergence increased
sharply from 17C at 24C water temperature to 23C at 25C water
temperature (Fig. 9). At water temperatures above 25C, the minimal
air temperatures necessary for emergence were inversely proportional


Figure 10. Body temperatures of Natrix taxispilota and
associated air temperatures at time of capture
at Nevaran's Lake.


lb 20 2b li 26 28 30 2 34
AIR TEMPERATURE (C)


Figure 11. Average body-air temperature differentials of
Natrix taxispilota at Newnan's Lake as a
function of air temperature. Data are the
same as those plotted in Figure 10. Numbers
in parentheses indicate number of snakes in
each category.


L
c4-0
13
<
cz.
LU
Q_
uj3-0
<
j
Cf. 2.0
3
5
c
UJ
E
1-0
Q
O
C3
20.1-22 22.1-24 24.1-26 26.1-28
AIR TEMPERATURE (C)
18.1-20
28.1-30


38
to water temperatures. This sharp increase in the minimal air temper
atures necessary to elicit emergence suggests that water is of con
siderable importance for thermoregulation between April and October
when such thermal conditions are common. When water temperatures
exceeded the PBT, emergence into lower air temperatures permitted
cooling to the preferred level. These water-air temperature differen
tials probably never obtain in nature, and ordinarily water tempera
tures appreciably above air temperature would occur in the evening
well after the emergence period.
The effect of acclimation on emergence
Animals used in the environmental room studies were adapted to
the air-water temperature combinations to which their responses are
graphed in Fig. 9. In the wild, this is not always the case. Sudden
climatic changes may result in exposure of snakes to a thermal environ
ment to which they are not physiologically adapted. For instance,
the same approximate air and water temperature ranges on February 20,
1971 and April 16, 1970 resulted in the emergence of 118 and 25 snakes
respectively (Fig. 12). Both days were relatively humid and windless
so the disparity seems to be a reflection of the difference in climatic
conditions during the week preceeding these dates. April 16 was warm
and typical of the weather of this period, and snakes were physio
logically acclimated to their PBT. February 20, however, was the
warmest day of a four day warming trend. Night air temperatures had
been at or near freezing until February 18. These snakes, then, were
acclimated to temperatures well below those of February 20 and the
basking response was greatly accentuated. These data and the re
lationship between acclimation temperature and PBT suggest that the
minimal air and water temperature combinations required to elicit emergence
and basking are lower in cold than in warm-acclimated snakes.


Figure 12. Number of Natrix taxispilota (bars) basking
at Newnan's Lake on various days throughout
the year (summation of data from 1969, 1970
and 1971) and the ranges of air temperature
(vertical lines) recorded at the Gainesville
weather station for those days.


NUMBER OF SNAKE
AIR TEMPERATURE RANGE (cC)


41
Effect of physiological state upon emergence
At 0920 on April 1, 1967, a snake was found basking with a body
o
temperature of 13.8 C. Corresponding air and water temperatures at
the time were 11.9C and 13.8C respectively. These were the lowest
body temperature and associated environmental temperatures recorded
during this study (Fig. 10). It is probably significant that this
individual had a prominent bulge from a fish it had recently eaten.
It is possible that the minimum air and water temperatures necessary
to evoke basking may be lower in snakes digesting food than in those
in a postabsorptive state. Presumably, higher body temperatures should
facilitate digestive processes in reptiles (Cowles and Bogert, 1944;
Regal, 1966).
Effect of light on emergence
Combinations of air and water temperatures ideal for basking did
not induce emergence at any hour in the absence of light. When the
sun lamp was turned on during the night, snakes basked if thermal
conditions were proper. Boyer (1965) found that turtles also
would bask in response to light at any time. During cloudy weather,
basking behavior was either diminished (i.e. fewer individuals emerged)
or emergence was delayed. Boyer, (1965) found this also to be true
for turtles. In the semiaquatic reptiles studied, therefore,
basking behavior does not appear to be an endogenous rhythm, but a
response to the proper conditions of light, water temperature, and
air temperature. The physiological state of the animal is an important
factor in determining the level of the environmental temperatures
necessary to induce emergence.
Figure 13 presents the thermal environment at Newnan's Lake on
April 9, 1970 and the emergence response of snakes. Climatic conditions


Figure 13.
The number of Natrix taxispilota basking at
Newnan's Lake at various times on April 9,
1970, and the associated air, water, and black
bulb temperatures.


NUMBER OF SNAKES
43
TEMPERATURE (C)


44
on this day were typical of the preceding:, week so these animals were
adapted to this general thermal regime. The water temperature exceeded
air temperature until 1200 hours but a peak in basking activity
occurred earlier. Emergence appeared to be initially triggered by the
onset of lighting, and to be accentuated by the rise in black-bulb
temperature.
Temporal changes in emergence response following initial onset of light
On many days, the initial air-water temperature combination used
was below the emergence threshold. Every two hours, air temperature
was raised 2C and responses were recorded. Under such conditions,
there occurred a temporal change in the snakes' propensity for emergnce.
Temperature combinations which would elicit emergence before about 1500
hours (EST) could not elicit initial emergence after that time. The
responses recorded in Fig. 9 were all recorded prior to 1500 hours.
The heating rate (a T = 2C/hr) and general warming pattern approximate
conditions occurring in the wild during winter. Under laboratory
conditions, 1500 hours occurred halfway through the "sunlight" cycle
(0900-2100 hours). In nature, six hours after sunrise would be
about 1300 hours EST during December and January. An animal initially
emerging after this time in response to threshold emergence temperatures
would begin to thermoregulate at or following the peak air temperature
of the day and would confront decreasing (and therefore sub-threshold)
air temperatures for the remainder of the day. Clearly, then, this
temporal restraint on the thermophilic emergence response is necessary
to restrict thermoregulatory activity to thermally hospitable periods.
Otherwise, extensive basking would occur at low body temperatures re
sulting in exposure of snakes to predation at suboptimal activity
temperatures.


45
Maintenance of Preferred Body Temperature
Elaborate behavioral adjustments permit some lizards to thermo-
regulate within very narrow limits. Desert lizards apparently have
the most elaborate behavioral repertoire, including postural adjust
ments (Bogert, 1949; Norris, 1953; Heath, 1965), retreat to burrows
(Cowles and Bogert, 1944; Norris, 1953; DeWitt, 1967a, 1967b; McGinnis,
1967), panting (Cole, 1943; Cowles and Bogert, 1944; Ruibal, 1961;
Kour and Hutchison, 1970), climbing (Norris, 1953; DeWitt, 1967a)
and burrowing (Cowles and Bogert, 1944; Heath, 1965) Physiological
modifications are known in these reptiles, but are clearly of secondary
importance in thermal homeostasis. Thermoregulation in snakes has been
studied very little and available information suggests that thermal
control is not as precise, and the behavioral repertoire not as
complex, as in the case of heliothermic lizards.
Following emergence, brown water snakes basked under the sunlamp
(or lay in the shade at higher air temperatures) until a body temperature
in the preferred range was reached and thereafter moved from the "sun,"
to shade, to water in order to maintain this level. No consistent
postural or coiling adjustments were noted. Retreat to the shade
or entrance into "sunlight" usually required 5 to 15 minutes. This
slow pace is probably the result of a slow heating and cooling rate
to be expected in an animal of such bulk and the wide range of pre
ferred temperatures.
At water temperatures below 25C (and appropriate air temperatures),
snakes emerged and basked in the "sunlight" until their PBT was reached
and then moved into the shade. There is a broad zone of overlap be
tween air temperature at which animals basked in the "sun" and those
at which they retreated to the shade. This appears to be largely a


46
reflection of the distance between the snake and the sunlamp; the
ecologic equivalent would be the directness and/or intensity of
sunlight. Similarly, there was overlap between the air temperatures
at which animals lay in the shade and those at which they entered
the water. This probably is a reflection of variation in body
temperature of the snake, from one experimental run to the next,
at the time it retreated from the "sunlight."
The lowest air temperature at which snakes retreated to shade
was, inversely proportional to water temperature at water temperatures
from 10C through 18C. Evidently, more time was required at these
low water temperatures (emergence body temperatures) for attainment
of preferred levels. This resulted in the recorded extreme of a
snake basking in the "sun" at an air temperature of 31C following
emergence from 10C water.
In one air-water thermal regime, snakes could be found in either
air, water, or "sun" (Fig. 9). This was between water temperatures of
approximately 23C and 27C and air temperatures of 23C and 28C.
These are evidently the only water temperatures above 10C at which
snakes may not emerge at all. At water temperatures above this
zone, there is a decline in the realm of air temperatures at
which emergent snakes bask in the sun, a marked increase in the
shade realm, and an extinction of the shade-sun overlap zone.
When air and water temperatures exceeded the preferred level,
snakes lay in the shade. These temperature combinations rarely or
never occur in nature and the value of such behavior is not clear.
In nature, extensive movement among the shade, sunlight, and
water usually occurs only in the late fall, winter, and early spring.
Low ambient temperatures at these times necessitate such thermo
regulatory behavior and the sparseness of foliage permits abundant


47
access to sunlight. At such times (Fig. 13) the number of individuals
basking usually peaks in late morning and declines thereafter. There
is an individual turnover and during the afternoon, submergence rate
exceeds emergence rate resulting in a decrease in the number of bask
ing individuals. The first individuals to attain PBT and eventually
reenter the water are probably the smaller animals since they heat
more rapidly. Data taken on March 5 substantiate this (Fig. 14).
Between 1100 and 1300 hours, there was an inverse relationship be
tween size of basking individuals and the body-air temperature
differential. No such correlation existed between 0900 and 1100 hours,
indicating that time of emergence was independent of body size. Figure
15 shows the changes in body temperature of a Natrix taxispilota, and
the associated environmental temperatures under natural climatic con
ditions of November 28, 1970, at Lake Alice.
During the warmer months (mid-April through mid-October), such
thermoregulatory behavior is seldom necessary, because air and water
temperatures during the day are usually within the PBT of this species.
Because of the level and wide range in PBT, snakes occasionally were
found to bask in one location from time of emergence until evening
submergence. Water temperatures during these months were often within
the preferred range, and most snakes either remained in the water or
had submerged by census time (Fig. 12).
Evening Submergence
With the approach of nightfall, few if any snakes remain on basking
sites above the water (Fig. 13). In initial laboratory experiments,
where lights came on at 0900 hours and went off at 2100 hours, snakes
usually emerged within an hour of onset of lighting (given proper
thermal conditions) and submerged within the 30-minute period after


Figure 14. The relationship between body size and body-air
temperature differentials of Natrix taxispilota
collected between .1100 and 1300 hours on
March 5, 1967.


TOTAL LENGTH (cm)
BODY TEMPERATURE AIR TEMPERATURE (C)
6*7


Figure 15
Changes in body temperature of a Natrix
taxispilota thermoregulating under natural
climatic conditions of November 28, 1970,
in experimental pen at Lake Alice.
snake in water
| [ snake in shade
snake in sun


(Do) 3flLV<$3dW31


52
light was terminated. After several weeks exposure to this photoperiod,
however, snakes often entered the water an hour or more before 2100 hours.
This evening submergence appears to be a temperature-independent
response to decreased light; snakes slide into the water regardless of
the air-water temperature differential. Boyer (1965^ noted that most
basking turtles left their basking sites and submerged prior to
30 minutes before sunset, although no mention was made of air and
water temperatures at these times. Since evening submergence is
evidently common in most semiaquatic reptiles, and since it is temperature-
independent (at least in Natrix taxispilota), this response probably
represents a predator avoidance behavior. Clearly much feeding --
almost exclusively on fish -- does occur at this time, when water
temperatures permit; but little feeding behavior probably occurs below
a water temperature (and therefore body temperature) of 15C (Lueth,
1941). Large fish could ingest small Natrix, but only alligators would
represent a substantial predation threat to brorni water snakes during the
aquatic phase of their activity cycle.
In natural situations, the water is usually warmer at night ,:i
than the air.; It may be, therefore, that evening submergence evolved
as a thermal response and persists even in the unnatural situations to
which snakes were subjected in the laboratory.
Factors Affecting Preferred Body Temperature
As previously mentioned, there appears to be a mutually causal
relationship between the level of physiological acclimation and PBT,
resulting in a fixed preferred level of about 25-30C throughout most
of the year. There are other ecologically relevant factors which may
alter the level of preferred temperature, at least temporarily.


53
Digestion
Snakes .acclimated to 25C were fed fish containing ingestible
transmitters and were found to regulate (in a gradient) at a warmer
end of the normal range (Table 2.). The same pattern was found in
animals that were given access to a heat lamp in an isothermal (21.0C)
environment. Two Natrix taxispilota were fed fish containing transmitters
and permitted to thermoregulate in this environmental chamber. The level
of air and water temperatures was low enough to induce basking but high
enough to permit attainment of body temperatures in excess of 30C
by basking under the sunlamp. The first day following feeding, these
snakes spent at least half the day in the water before emergence. This
delayed emergence is probably unrelated to thermoregulatory behavior. It
is a common behavioral trait of captive snakes, including terrestrial
species, to submerge in any available water after consuming a large
meal. The moisture evidently facilitates stretching of the skin, or
at least provides better support for the portion of the body containing
the food. Upon emergence, snakes maintained body temperatures mostly
between 27.5C and 31cC. When they first emerged, the snakes usually
lay with the bolus directly under the sunlamp and moved to a cooler
area after body temperature reached 30C to 32C. A four-day thermal
record for one of these snakes is shown in Fig. 16.
Thermophilic responses to feeding have been reported for other
reptiles (Regal, 1966; Bustard, 1967; Kitchell, 1969) including two
semiaquatic snakes, Natrix sipedon and Thamnophis sirtalis. In all
cases, the preferred thermal range following feeding seems to con
stitute a sub-range of the postabsorptive PBT. This increase in pre
cision of thermoregulation has in all cases been interpreted as a
facilitation of digestive processes.


Figure 16. Four-day body temperature record of a Natrix
taxispilota digesting a fish eaten on March 23,
1971. Throughout the first day of digestion,
the snake remained in the water (see text);
the subsequent four-day period is shown. Air
and water temperature were maintained at 21C.
Dark bars indicate periods of darkness; light
bars indicate periods of light.


ODY TEMPERATURE (C)
HOUR


56
The effect of temperature on digestive efficiency was determined
for Natrix taxispilota at 20, 25, 30, and 35C. The greatest extraction
efficiency occurred at 30C (Fig. 17) and decreased both above and below
this temperature. This thermal level corresponds to the preferred
level for digestion (Table II). Regurgitation of food was very common
among snakes maintained at 35C, another indication that this was
supraoptimal thermal level for digestion. Below 30C, digestive
efficiency decreased with decreasing temperature but the 82.6 percent
efficienty level at 20C is still a substantial figure. It is obvious
that high body temperatures expedited digestion but were not absolutely
necessary, indicating that under natural conditions, digestive processes
would continue at night well after submergence if water temperature was
not excessively cold. This wide range of digestive activity is probably
necessary in such poikilotherms to prevent putrefaction of ingested
food at night and during other periods when body temperature falls well
below 30C. Putrefaction would be a particularly great problem in
snakes since they ingest items whole and the internal tissue of in
gested items would not be reached by gastric enzymes for many hours
or days if digestion ceased at temperatures slightly below the optimal
level.
The influence of temperature on gastric digestion in the European
grass snake, Natrix natrix, was studied by Skoczylas (1970) who used
x-ray photography to determine the speed of digestion at temperatures
of 5, 15, 25, and 35C. He found that digestion was completely
arrested at 5C and proceeded very slowly (or ended in regurgitation)
at 15C. Digestion was complete at both 25 and 35C but was faster
at 25C. Digestive rates in the king snake, Lamnropeltis getulus,
were found by Root (1961) to be similar to those of N. natrix below


57
BODY TEMPERATURE (C)
Figure 17. The effect of temperature on digestive extraction
efficiency of Natrix taxispilota. Horizontal line,
mean; vertical bar, standard deviation; vertical
line, range.


Table 2
PBT RANGE (C)
MEAN
Effect of digestion on the normal range of
preferred body temperatures.
POSTABSORPTIVE DIGESTING
25.7 32.6 28.2-32.1
29.86 30.28
N (OBS.)
5 (66)
4 (49)


59
25C, but the maximum digestive rate occurred at the highest temperature
employed, 33C. Skoczylas attributed the discrepancy in digestive rates
of the two species at 33-35C to intraspecific differences in PBT.
Research on digestive rates of other poikilotherms tends to substantiate
this generalization. Many freshwater fish are able to digest food at
2C to 5C (Wangensteen et al., 1958; Molnar and Tlg, 1962). These
temperatures are below the lower limit of the thermal activity range
of Spenodon punctatus, the lowest known for any reptile (Bogert, 1953a,
1953b). In fish studied over a wide range, digestive rate appears to
be directly correlated with water temperature (Riddle, 1909). However,
the rate of food input may also influence digestive efficiency. Davies
(1964) found that in Carassius auratus, the proper level of food input
could increase extraction efficiency to 92-94 percent at either 21.5C
or 12C. Other workers (Ivlev, 1939; Gerking, 1955) have found extraction
efficiencies of other fish at a given temperature to be independent of
input rate. Amphibians also show wide thermal ranges for digestion
(Pegel, 1939; Joly, 1958; Root, 1961) and are capable of digesting at
temperatures less than 10C, levels at which peristalsis ceases in most
reptiles (Skoczylas, 1970). The processes of gastric digestion and
peristalsis may have different thermal thresholds, as in the painted
turtle, Clirysemys picta, which cannot digest, but maintains peristalsis,
at 5C (Fox and Masacchia, 1959). Nonheliothermic poikilotherms, there
fore, seem to have lower thermal thresholds for digestive processes than
heliothermic species.
Other Factors Affecting Preferred Body Temperature
Regal (1967) clearly demonstrated that several species of lizards
placed in a gradient will select night temperatures that are well be
low their preferred diurnal PET. This was true of Klauberina riversiana,


60
a nocturnally-active lizard, as well as three heliothermic
diurnally-active forms. No such endogenous variation in the level
of PBT was found in Natrix taxispilota maintained in a gradient.
From April through October, water temperatures at the study site
were generally warmer at night than air temperatures. A voluntary
hypothermic response to darkness would therefore be inconsistent with
their behavior. Evening submergence appeared to be a temperature-
independent response to diminished light.
The data of Kitchell (1969) suggest that snakes undergoing
ecdysis actively select body temperatures below their normal PBT.
The three species he investigated included two semiaquatic species,
Thamnophis sirtalis and Natrix sipedon. The latter, when not shedding,
had a PBT of 28.03 + .28C (mean + standard deviation) but a preference
of 18.71 + .38C when undergoing ecdysis. In the present study, there
were not enough data available to detect such voluntary hypothermic
response to ecdysis but, in view of the unanimity of Kitchell's data
for three species of snakes -- one congeneric with N. taxispilota --
it seems likely that brown water snakes have lower thermal preferenda
when shedding.
No pregnant females were used in this study but data from several
sources suggest that such individuals have thermal preferences that
differ from those of males and non-pregnant females. Stewart (1965)
found in Thamnophis sirtalis and T. ordinoides "a consistent tendency
for pregnant females of both species to maintain relatively high body
temperatures." Fitch (1960) found that gravid female copperheads,
Ancistrodon contortrix, regulated within more precise limits than males
or non-pregnant females and noted that "most of the copperheads found
basking in sunshine in summer were females."- Osgood (1970) found


61
pregnant female Natrix taxispilota and N. faseiata to thermoregulate
within a narrower temperature range than males or non-pregnant females,
but his sample for Natrix taxispilota consisted of only four individuals
(three pregnant females, one male). In all of these accounts, the body
temperatures fell within the limits of the normal PBT but constituted
a smaller sub-range within it.
The effect of intraspecific differences in size upon PBT has been
examined by several workers, inter alia Bogert (1949), Wilhoft (1958),
Hirth (1963), and Brooks (1968). Only in Basiliscus vittatus (Mirth,
1963) were statistically significant differences found and the differences
were so slight (35.3 + 0.05C in juveniles, 34.7 + 0.07C in adults) that
ecological significance cannot be ascribed. The most likely candidate
for an ecologically significant change in PBT with size is probably
Varanus komodoensis, the world's largest lizard. This species is
arboreal as a juvenile and becomes terrestrial upon attaining the
length of 1.5 to 2.0 meters (Walter Auffenberg, private communication).
It would be surprising if a change in PBT did not accompany this change
in habitat preference.
The PBT in a given species of reptile, then, is not an immutable
thermal level. It may undergo temporal changes and changes reflecting
the thermal optima for various physiological processes. It has long
been known that snakes undergoing ecdysic processes refuse to feed.
This behavior pattern has been interpreted as a response to avoid
damage to the newly developing epidermal layer which would be severely
stretched or even split by the ingestion of large items. The pre
ceding discussion of the thermal requirements of these two processes
(eedysis and digestion) in reptiles, suggests a thermal incompatibility
and certainly presents at least as strong an argument for their non
concurrence .


62
The Ecological Significance of Reptilian Preferred Body Temperature
Many workers (Ruibal, 1961; Brattstrom, 1965; Kitchell, 1969;
Skoczylas, 1970) have commented on the empirical relationship be
tween the PBT of reptiles and the microclimate of their habitat.
Again, these generalizations deal mostly with lizards. Diurnally-
active desert lizards generally have higher PBTs than lizards from
non-desert areas. Diurnal reptiles generally have higher thermal
preferenda than nocturnal species. Surprisingly, the significance
of this relationship has never been examined from the standpoint of
causality. Existing data on reptilian thermal preferences and tolerances
suggest that climate may be a major factor in evolutionarily setting'
the level of PBT.
The thermal extremes between which reptiles must live are the
approximate levels that freeze their tissues and those that denature
their proteins, or in other ways cause physiological heat-death. But
most, if not all, reptiles keep their body temperature from varying
with environmental temperature, by maintaining it at a certain level
within this 50C span. Evolutionarily, reptiles can choose the ceiling
of their preferred range by behaviorally utilizing solar energy.
Empirical evidence of this is the occupation by several species of
reptiles with different PBTs of a common habitat (Cowles and Bogert,
1944; Bogert, 1959; Soule,.1963). However, the thermal characteristics
of the environment leave less evolutionary choice in the lower threshold
of the PST because reptiles lack the cooling mechanisms characteristic
of most mammals and birds (Schmidt-Nielsen and Dawson, 1964) and can
therefore cool only to the level of the coolest segment of their environ
ment. Summer shade temperatures in North America set this lower utilizable


o o
level at about 20 C to 23 C for diurnally-active terrestrial reptiles.
Thus, the observation that PBT is generally closer to the critical
1 2
thermal maximum than to the critical thermal minimum is to be expected,
because the thermal range between critical thermal minimum and 20-23C
is unavailable. However, many diurnal reptiles operate at thermal
levels only a few degrees below temperatures that cause irreversible
tissue damage. The question, therefore, becomes why do not all
diurnally active reptiles choose PBTs of about 25-35C and leave
margins of safety at both ends? The answer is apparently related to
(1) the biological effects of thermal extremes and (2) the correlation
between PBT and the critical thermal maximum.
Hypothermia slows the rates of physiological processes, but rarely
causes irreversible damage above 0C. However, irreversible tissue
damage is incurred at temperatures above about 44C. These temperatures
slightly exceed the highest air temperature (though certainly not the
highest black-bulb temperature) to which a diurnal animal could expect
to be exposed in its normal activity and natural habitat. There is a
direct correlation between the preferred level of body temperature and
the level of critical thermal maximum (Schmidt-Nielsen and Dawson, 1964;
Brattstrom, 1965; see Fig. 18). The highest body temperature a reptile
will ever attain must be below the CTMax if that animal is to survive,
and this body temperature should be directly related to the highest air
temperature experienced. These environmental thermal extremes are
^"The thermal point at which locomotory activity becomes dis
organized and the animal loses its ability to escape from conditions
that will promptly lead to its death" (Cowles and Bogert, 1944).
2
"The temperature that causes a cold narcosis and effectually
prevents locomotion" (Cowles and Bogert, 1944).


The relationship between preferred body temperature
and critical thermal maximum in reptiles (x = .59)
Data are from Brattstrom (1965) for species with
sample sizes of 20+.
Figure 18.


65


66
selective factors which set the level of CTMax by eliminating the
individuals with lowest thermal tolerance. Since CTMax bears a re
lationship to PBT, that is apparently genetically fixed, there should
be a direct correlation between these environmental extremes and PBT.
Furthermore, the PBT of a reptile should be more strongly correlated
with the highest temperature recorded in its habitat than with any
mean high temperature value because the latter are clearly of less
evolutionary significance in fixing the level of CTMax.
2
Figure 19 shows the high correlation (r = 0.61) between PBT in
3
several primarily heliothermic species of reptiles and the highest
temperature ever recorded at the weather station nearest the collection
locality (Kincer, 1941). Studies that failed to list collecting
locality, or for which no such weather data could be found, are excluded.
Data from studies in which field body temperatures constituted the
basis for determination were included only if the sample size exceeded
20 and observational correlations were made. When these conditions
are met, PBT and mean body temperature (Peters, 1964) become synonymous
and comparison between these values is valid. The pertinent statistical
data and references are listed in Table 3.. .
As expected, the correlation with PBT is significantly greater
for maximum temperature than for the mean temperature of the hottest
month (July in the northern hemisphere, January in the southern). This
supports the hypothesis that the level of PBT is indirectly fixed
evolutionarily by its relationship to the level of CTMax, which is
directly fixed by high environmental temperature extremes. This does
3
A primary heliotherm is here defined as a diurnally-active lizard
inhabiting an open habitat (or habitats) that offer access to sunlight
throughout the day.


Figure 19.
Relationship between preferred body temperature of
primary heliotherms and the highest air temperature
recorded in the area from which they were collected.
Statistical information and sources for the data
are listed in Table 3.


PREFERRED BODY TEMPERATURE (C)
ON
00


69
Table 3. Data for points plotted in Figure 19 for
primary heliothermic lizards.
NUMBER IN
FIG. 19
SPECIES
N
PBT
SOURCE
1
Anolis allisoni
122
33.0
Ruibal, 1961
2
Anolis homolechis
104
31.8
Ruibal, 1961
3
Anolis sagrei
178
33.1
Ruibal, 1961
4
Crotaphytus collaris
425+
38.0
Fitch, 1956
5
Dipsosaurus dorsalis
M*
38.5
DeWitt, 1967b
6
Sauromalus obesus
49
37.7
Cowles and Bogert, 1944
7
Sceloporus graciosus
70
32.3
Mueller, 1969
8
Sceloporus occidentalis
500+
35.0
Larson, 1961
9
Sceloporus orcutti
21
35.4
Mayhew, 1963
10
Urosaurus ornatus
97
35.5
Brattstrom, 1965
11
Cnemidophorus sexlineatus
M*
39.5
Fitch, 1956
12
Sceloporus woodi
42
36.0
Bogert, 1949
13
Cnemidophorus tesselatus
33
41.3
Bogert, 1949
14
Amphibolorus barbatus
58
34.8
Lee and Badham, 1963
15
Amphibolorus inermis
M
36.8
Pianka, 1971
MAXIMUM
TEMP.
MEAN
HIGH TEMP.
CORRELATION COEFFICIENT 0.78
0.54
EQUATION
FOR LINE Y = .492X + 14.46

many


70
not mean, however, that the absolute level of PBT is solely a function
of high air temperature extremes. Any species-specific behavior
(burrowing, panting, etc.) that meliorates the severity of such
extremes will be of selective advantage. It is the interaction of
these behavior patterns and physiological tolerances that, under the
selective pressures of high temperatures, will determine the level of
PBT. Interspecific differences in behavior and physiological tolerance
will result in the utilization by several species with slightly different
PBTs of a common habitat.
By setting their body chemistry to operate optimally at a given
temperature, reptiles concomitantly- must accept diminished levels
of 'metabolic efficiency' at non-optimal temperatures. At body
temperatures below PBT, metabolism merely slows down as a function of
temperature (Fig. 20), and normal activity, such as food procurement,
ceases. But, at such times, the animal incurs no tissue damage and
the decreased level of metabolism is compatible with decreased digestive
efficiency (and therefore energy availability) and food consumption.
At temperatures above PBT, however, the decreased levels of digestive
efficiency (and metabolic efficiency generally) and food consumption
coincide wTith an increase in metabolism. In addition, very high
temperatures will cause irreversible tissue damage. So by choosing
relatively high body temperatures, heliotliermic reptiles avoid the
problem of overheating and are penalized by having to remain inactive
or suboptimally active on-cool days. The opposite strategy of choosing
a low PBT to insure more days of activity entails the risk of over
heating to the point of death. This, as mentioned, is probably the
mechanism that sets the level of reptilian PBT evolutionarily. High
thermal extremes will eliminate the least heat tolerant (lowest CTMax)


Figure 20. The effect of temperature on the metabolic rate
of a 509 g Natrix taxispilota at two acclimation
temperatures, (A) 20 and (B) 25.


BODY TEMPERATURE (C)
METABOLISM (cc02/hr)
ZL


individuals and select for a species with a higher CTMax (and PBT).
Theoretically, a reptile's CTMax should be just above the highest
ambient temperature (and body temperature) the species ever encountered
in its normal habitat during its normal period of activity. Therefore,
diurnal terrestrial species should have higher PBTs than nocturnal
terrestrial species.
Still, the highest daytime air temperature recorded in an area
should be correlated with the highest night temperature. A correlation,
then, does exist between PBT of nocturnal reptiles and highest air
temperature (Fig. 21). The correlation is weaker than with primarily
heliothermic species, as would be expected. Between the lines relating
PBT with highest air temperature in primary heliothermic species and in
nocturnal species, there are a series of points which form a third line
with an intermediate slope. The points are for diurnally-active snakes
and forest lizards. The lizards (Anolis and Eumeces) bask (in patches
of sunlight reaching the forest floor) but not nearly as extensively
as primary heliothermic species. However, the heliothermic snakes
(Coluber and Heterodon) occur in the same open habitats in which
heliothermic lizards maintain higher PBTs. This suggests that the
differences in thermal preferenda of snakes and lizards may be a
function of differences in the ecology of the two groups. The nocturnal
species used to determine line A (Fig. 21) were, with one exception
(the Gila monster, Heloderma suspectum), all snakes, so it is impossible
to determine from these data whether their lower thermal preferenda
exist because they are nocturnal or because they are snakes, or both.
One consistent characteristic of snakes that separates them from
almost all lizards suggests a basis for a lower PBT. This is the
absence of legs. The thermoregulatory significance of this is that


PREFERRED BODY TEMPERATURE (C)
74
Figure 21. Relationship between reptilian preferred body
temperature and the highest air temperature re
corded in the collection area. A. nocturnal
reptiles (circles). B. diurnal snakes and forest
lizards (squares;. C. primary heliothermic lizards
(from Figure 17). Statistical information and sources
for data are listed in Table 4 (line A) and Table 5
(line. B).


Table 4. Data for
nocturnal
points plotted
reptiles (line
in Fig
A).
ure 21 for
NUMBER IN
FIG. 21
SPECIES
N
PBT
SOURCE
1
Heloderma suspectum
57+
28.7
Bogert and del Campo, 1956
2
Elaphe obsoleta
53
28.0
Fitch, 1956
3
Thamnophis sirtalis
157
25.6
Carpenter, 1956
4
Thamnophis sirtalis
108
29.3
Kitchell, 1969
5
Thamnophis sirtalis
21
29.5
Fitch, 1965
6
Thamnophis sirtalis
M
28.0
Stewart, 1965
7
Thamnophis ordinoides
M
27.4
Stewart, 1965
8
Thamnophis sauritus
123
26.0
Carpenter, 1956
9
Thamnophis butleri
54
26.1
Carpenter, 1956
10
Natrix sipedon
114
28.0
Kitchell, 1969
11
Matrix taxispilota
4S "
27.5
Present paper
12
Ancistrodon mokeson
73
27.0
Fitch, 1956, 1960
13
Crotalus cerastes
M
31.4
Cowles and Bogert, 1944
MAXIMAL TEMP. MEAN HIGH TEMP.
CORRELATION COEFFICIENT 0.68 0.65
EQUATION FOR LINE
Y = .368X + 12.07


76
Table 5. Data for points plotted in Figure 21 for
diurnal snakes
and forest lizards (line B).
NUMBER IN
FIG. 21
SPECIES
N
PBT
SOURCE
14
Anolis allogus
148
29.2
Ruibal, 1961
15
Anolis lucius
86
29.3
Ruibal, 1961
16
Eumeces fasciatus
41+
33.0
Fitch, 1954, 1956
17
Eumeces obsoletus
M
34.0
Fitch, 1955
18
Coluber constrictor
29
30.9
Fitch, 1956
19
Coluber constrictor
127
31.5
Kitchell, 1969
20
Heterodon platyrhinos
102
31.8
Kitchell, 1969
MAXIMUM TEMP. MEAN HIGH TEMP.
CORRELATION COEFFICIENT 0.81 0.48
EQUATION FOR LINE
Y = 0.344X f 40.27


77
terrestrial snakes are in more intimate physical contact with their
environment and more vulnerable to conductive heat exchange with the
substrate. This, in part, explains why Carpenter (1956), in his
study of thermoregulation in three species of garter snakes, found
cloacal temperatures to be more closely correlated with the temperature
at the ground surface than with air temperature above or soil temperature
below. Desert lizards rely greatly on such conductive heat exchange as
a cooling mechanism. The desert iguana, Dipsosaurus dorsalis, presses
its venter from side to side in the sand exposing cooler layers to
which it loses body heat by conduction (Norris, 1953). At higher
temperatures, lizards retreat to burrows (DeWitt, 1967a, 1967b;
McGinnis, 1967; Norris, 1953) again relying on conductive heat exchange
to reach the preferred thermal level. The high surface temperatures
characteristic of desert regions frequently exceed the preferred body
temperatures of the reptiles occurring there. While a heliothermic
tetrapod can hold its body above this substrate and thermoregulate with
a degree of independence of it, snakes cannot. This undoubtedly at
least partly accounts for the paucity of diurnally active snakes in
desert areas where lizard species are abundant. And a nocturnal
activity pattern preordains a relatively low PBT.
If the absence of legs is of significance in determining the level
of PBT, diurnally-active legless lizards should fall on line B (Fig. 21)
with diurnal snakes. The only data available for such lizards are for
the species Ophisaurus attenuatus (Fitch, 1956) in Kansas. Field
temperatures of 15 active individuals collected on clear days ranged
between 30.6C and 33.7C. The mean value of 32.2C would fall 1.4C
below the diurnal snake-forest lizard line. This is good agreement even
though this point was based on a sample size too small to warrant its
inclusion in Fig. 21.


SUMMARY
Thermoregulatoiy behavior under natural and laboratory conditions
was studied in the brown water snake Matrix taxispilota.
The effect of temperature on digestive extraction efficiency was
determined calorimetrically.
The effect of acclimation on metabolic rate and preferred body
temperature was determined.
There is an inverse relationship between preferred body temperature
and acclimation temperature in brown water snakes. A seasonal change
in preferred body temperature occurs in nature.
There is an inverse relationship between thermal level of acclimation
and metabolic rate at a given temperature. Metabolism becomes accli
mated to the highest of varying temperatures to which the snake is
exposed in a 24-hour period.
There are lower air and water threshold temperatures for emergence
in brown water snakes. Factors affecting the levels of these
thresholds include thermal acclimation and physiological state
of the animal.
Matrix taxispilota will not emerge at any air and water temperatures
in the absence of light.
There are temporal changes in the propensity for emergence after
initial onset of light.
Thermoregulatory responses of brown water snakes to various thermal
regimes are described and discussed.
There is a temperature-independent evening submergence response in
Matrix taxispilota.


79
11. Brown water snakes digesting food thermoregulate at a sub-level
within the normal preferred body temperature range.
12. Digestive efficiency is greatest at about 30C and decreases above
and below this level.
13. It is suggested that high thermal extremes directly fix the critical
thermal maximum of reptiles and indirectly fix the preferred body
temperature. Supportive evidence is presented and discussed.
14. The absence of legs in snakes precludes thermoregulation with the
degree of independence of conductive heat exchange with the substrate
enjoyed by most lizards. It is suggested that this may, in part,
account for the relatively low preferred body temperatures of
snakes.


LIST OF REFERENCES
Bailey, Reeve M. 1949. Temperature tolerance of gartersnakes in
hibernation. Ecology 30: 238-242.
Bartholomew, George A. and V. A. Tucker. 1963. Control of changes in
body temperature, metabolism, and circulation by the agamid lizard,
Amphibolurus barbatus. Physiological Zoology 36: 199-218.
Berg, Kaj. 1953. The problem of respiratory acclimation. Hydro-
biologica 5: 331-350.
Bogert, Charles M. 1949. Thermoregulation in reptiles, a factor in
evolution. Evolution 3: 195-210.
Bogert, Charles M. 1953a. Body temperatures of the Tuatara under
natural conditions. Zoolgica 38: 63-64.
Bogert, Charles M. 1953b. The tuatara: Why is it a lone survivor?
Hie Scientific Monthly 76: 163-170.
Bogert, Charles M. 1959. How reptiles regulate their body temperature.
Scientific American 200: 105-120.
Bogert, Charles M. and Rafael Martin del Campo. 1956. The gila monster
and its allies: the relationships, habits, and behavior of the
lizards of the family Helodermatidae. Bull. Amer. Mus. Nat. Hist.
109: 1-238.
Boyer, Don R. 1965. Ecology of the basking habit in turtles. Ecology
46: 99-118.
Bradshaw, D. 1965. The comparative ecology of lizards of the genus
Amphibolurus. Ph.D. thesis, University of Western Australia.
Brattstrom, Bayard H. 1952. Diurnal activities of a nocturnal animal.
Herpetologica 8: 61-63.
Brattstrom, Bayard H. 1965. Body temperatures of reptiles. Amer.
Midi Nat. 73: 376-422.
Brett, J. R. 1944. Some lethal temperature relations of Algonquin
Park fishes. Publ. Ontario Fish Res. Lab. 63: 1-49.
Brooks, Garnett R. 1968. Body temperatures of three lizards from
Dominica, West Indies. Herpetologica 24: 209-214.
Bullock, Theodore Holmes. 1955. Compensation for temperature in the
metabolism and activity of poikilotherms. Biological Reviews
30: 331-342.
80


81
Bustard, H. R. 1967. Activity cycle and thermoregulation in the
Australian gecko, Gehyra variegata. Copeia 1967: 753-758.
Carpenter, Charles C. 1956. Body temperatures of three species of
Thanmophis. Ecology: 372-375.
Cole, LaMont C. 1943. Experiments on toleration of high temperature in
lizards with reference to adaptive coloration. Ecology 24: 94-108.
Cowles, Raymond B. 1958. Possible origin of dermal temperature
regulation. Evolution 12: 347-357.
Cowles, Raymond B. and Charles M. Bogert. 1944. A preliminary study
of the thermal requirements of desert reptiles. Bull. Amer. Mus.
Nat. Hist. 83: 265-296.
Davies, P. M. C. 1964. The energy relations of Carassius auratus L. --
I. Food input and energy extraction efficiency at two experimental
temperatures. Comp. Biochem. Physiol. 12: 67-79.
DeWitt, Calvin B. 1967a. Behavioral thermoregulation in the desert
iguana. Science 158: 809.
DeWitt, Calvin B. 1967b. Precision of thermoregulation and its
relation to environmental factors in the desert iguana, Dipsosaurus
dorsalis. Physiol. Zool. 40: 49-66.
Fitch, Henry S. 1954. Life history and ecology of the five-lined skink,
Eumeces fasciatus. Univ. Kansas Publ., Mus. Nat. Hist., 8: 1-156.
Fitch, Henry S. 1955. Habitats and adaptations of the great plains
skink (Eumeces obsoletus). Ecol. Monog. 25: 59-83.
Fitch, Henry S. 1956. Temperature responses in free-living amphibians
and reptiles of Northeastern Kansas. Univ. Kan. Publ., Mus. Nat.
Hist., 8: 417-476.
Fitch, Henry S. 1965. An ecological study of the garter snake
Thamnophis sirtalis. Univ. Kan. Pulb., Mus. Nat. Hist., 15: 493-564.
Fitch, Henry S. i960. Autecology of the copperhead. Univ. Kan. Publ.,
Mus. Nat. Hist., 13: 85-288.
Fox, V. M. and X. J. Masacchia. 1959. Notes on the pH of the digestive
tract of Chrysemys picta. Copeia 1959: 337-339.
Fry, F. E. J. 1958. Temperature compensation. Annual Review of
Physiology 20: 207-224.
Fry, F. E. J. 1964. Animals in aquatic environments: fishes. 715-728.
In: D. B. Dill (ed.). Handbook of Physiology. Sect. 4. Adaptation
to the environment. Amer. Phy^siol. Soc., Washington, D. C.
Fry, F. E. J., J. S. Hart, and K. F. Walker. 1946. Lethal temperature
relations for a sample of young speckled trout (Salvelinus frontinalis).
Univ. Toronto Stud. Biol. 55: 9-35.


82
Gerking, S. D. 1955. Influence of rate of feeding on body composition and
protein metabolism of blue-gill sunfish. Physiological Zoology,
28: 267-282.
Heath, J. E. 1965. Temperature regulation and diurnal activity in
horned lizards. Univ. Calif. Publ. Zool. 64: 97-136.
Heath, W. G. 1963. Thermoperiodism in sea-run cutthroat trout (Salmo
clarki clarki). Science 142: 486-488.
Hirth, H. F. 1963. The ecology of two lizards on a tropical beach.
Ecological Monographs 33: 83-112.
Hutchison, Victor H., Herndon G. Dowling, and Allen Vinegar. 1966.
Thermoregulation in a brooding female Indian python, Python
molurus bivittatus. Science 151: 694-696.
Hutchison, Victor H. and Michael R. Ferrance. 1970. Thermal tolerances
of Rana pipiens acclimated to daily temperature cycles. Herpetologica
26: 1-8.
Ivlev, V. S. 1939. Balance of energy in carps. Zool. Zh. 18: 303-318.
Joly, J. 1958. Influence des basses temperatures sur cycle alimentaire
de quelques tritons Franjis. Bull. Soc. Zool. Fr. 83: 128-131.
Kincer, J. B. 1941. Climate and weather data for the United States.
Yearbook of Agriculture: "Climate and Man." Washington, D.C.,
U.S. Gov't. Printing Office, 185-699.
Kitchell, James F. 1969. Thermophilic and thermophobic responses of
snakes in a thermal gradient. Copeia 1969: 189-191.
Kour, Edna Lynne and Victor H. Hutchison. 1970. Critical thermal
tolerances and heating and cooling rates of lizards from diverse
habitats. Copeia 1970: 219-229.
Larson, Mervin W. 1961. The critical thermal maximum of the lizard
Sceloporus £. occidentalis Baird and Girard. Herpetologica
17: 113-122.
Lee, Anthony K. and Judith A. Badham. 1963. Body temperature, activity,
and behavior of the agamid lizard, Amphibolurus barbatus. Copeia
1963: 387-394.
Licht, Paul. 1968. Response of the thermal preferendum and heat resistance
to thermal acclimation under different photoperiods in the lizard Andis
carolinensis. Amer. Midi. Nat. 79: 149-158.
Licht, Paul and Allen G. Brown. 1967. Behavioral thermoregulation and
its role in the ecology of the red-bellied newt, Taricha rivularis.
Ecology 48: 598-611.
Lowe, Charles H., and Velma J. Vance. 1955. Acclimation of the critical
thermal maximum of the reptile Urosaurus ornatus. Science 122: 73-74.


83
Lucas, E. A. and W. A. Reynolds. 1967. Temperature selection by
amphibia larvae. Physiological Zoology 40: 159-171.
Lueth, F. X. 1941. Effects of temperature on snakes. Copeia 1941:
125-132.
Mackay, R. Stuart. 1964. Galapagos tortoise and marine iguana deep
body temperatures measured by radio telemetry. Nature 204: 355-458.
Mayhew, W. W. 1963. Temperature preferences of Sceloporus orcutti.
Herpetologica 18: 217-233.
McGinnis, S. M. 1967. Telemetry applied to studies of thermoregulation
in reptiles. Proc. 1967 Nat. Telemet. Conf.: 252-254.
McGinnis, Samuel M. and Robert G. Moore. 1969. Thermoregulation in the
boa constrictor, Boa constrictor. Herpetologica 25: 38-45.
Molnar, G. and I. Tolg. 1962. Relation between water temperature and
gastric digestion of largemouth bass, Micropterus salmoides Lacepede.
J. Fish. Res. Bd. Can. 19: 1005-1012.
Mueller, Charles F. 1969. Temperature and energy characteristics of the
sagebrush lizard (Seeloporus graciosus) in Yellowstone National Park.
Copeia 1969: 153-160.
Myres, Brian C. and Murray M. Eells. 1968. Thermal aggregation in Boa
constrictor. Herpetologica 24: 61-66.
Norris, Kenneth S. 1953. The ecology of the desert iguana, Dipsosaurus
dorsalis. Ecology 34: 265-287.
Norris, Kenneth S. 1963. The functions of temperature in the ecology of
the percoid fish Girella nigricans (Ayres). Ecological Monographs
33: 23-62.
Osgood, David. 1970. Thermoregulation in water snakes studied by telemetry.
Copeia 1970: 568-571.
Pegel, W. A. 1939. Motornaja finkeija pistchevaritelnoj sistemy ryb v
uslovijach razlitschnoj temperatury sredy. Trudy biol. Nauchno-issled.
Inst, tomsk. gos Univ. 6: 51-67.
Peters, James A. 1964. Dictionary of Herpetology. Hafner Publishing
Company, New York.
Pianka, Eric R. 1971. Comparative ecology of two lizards. Copeia 1971:
129-138.
Regal, P. J. 1966. Thermophilic responses following feeding in certain
reptiles. Copeia 1966: 588-590.
Regal, P. J. 1967. Voluntary hypothermia in reptiles. Science 155: 1551-1553.
Riddle, 0. 1909. The rate of digestion in cold-blooded vertebrates --
influence of season and temperature. Am. J. Physiol. 24: 447-458.
the


84
Root, H. D. 1961. Gastric digestion with hypothermia: observations
and applications. Thesis, University of Minnesota, 1-154.
Ruibal, Rodolfo. 1961. Thermal relations of five species of tropical
lizards. Evolution 15: 98-111.
Schmidt-Nielsen, Knut and William R. Dawson. 1964. Terrestrial animals
in drj, heat: desert reptiles. 467-480. In: D. B. Dill (ed.).
Handbook of Physiology. Sect. 4. "Adaptation to the Environment."
Amer. Physiol. Soc., Washington, D. C.
Skoczylas, Rafa. 1970. Influence of temperature on gastric digestion in
the grass snake Natrix natrix L. Comp. Biochem. Physiol. 33: 793-804.
Soule, Michael. 1963. Aspects of thermoregulation in nine species of
lizards from Baja, California. Copeia 1963: 107-115.
Stewart, Glenn R. 1965. Thermal ecology of the garter snakes Thamnophis
sirtalis concinnus (Hallowell) and Thamnophis ordinoides (Baird and
Girard). Herpetologica 21: 81-102.
Wangensteen, 0. H., H. D. Root, C. B. Jenson*, K. Imamoglu, and P. A. Salmon.
1958. Depression of gastric secretion and digestion by gastric hypo
thermia. Its clinical use in massive hematomesis. Surgery 44: 265-274.
Weathers, Wesley W. 1970. Physiological thermoregulation in the lizard
Dipsosaurus dorsalis. Copeia 1970: 549-557.
Wilhoft, D. C. 1958. Observations on preferred body temperatures and
feeding habits of some selected tropical iguanas. Herpetologica
14: 161-164.
Wilhoft, D. C. and J. D. Anderson. 1960. Effect of acclimation on the
preferred body temperature of the lizard Sceloporus occidentalis.
Science 131: 610-611.


BIOGRAPHICAL SKETCH
Donald Eugene Goodman was born January 30, 1944, at Kennett,
Missouri. In June, 1966, he received the degree of Bachelor of
Arts with a major in Zoology from the University of Missouri. In
1966, he enrolled in the Graduate School of the University of Florida
and has until the pi'esent time pursued his work toward the degree of
Doctor of Philosophy in the Department of Zoology.
Donald Eugene Goodman is a member of the American Society of
Ichthyologists and Herpetologists and the American Association for
the Advancement for Science.
85


I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.
A. F. Carr, Jr., Chairman
Graduate Research Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.
Siifikt
B. K. McNab, Co-Chairman
Associate Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.
G. Nordlie
Associate Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.
E. S. Ford
Professor of Botany


This dissertation was submitted to the Dean of the College of Arts
and Sciences and to the Graduate Council, and was accepted as partial
fulfillment of the requirements for the degree of Doctor of Philosophy.
June, 1971
Dean, Graduate School


Full Text
Thermoregulation in the Brown Water Snake, Matrix taxispilota,
with Discussion of the Ecological Significance of
Thermal Preferencia in the Order Squamata
By
DONALD EUGENE GOODMAN
A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL OF
THE UNIVERSITY OF FLORIDA IN PARTIAL
FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1971

This work is dedicated to my parents, Arvil E, Goodman and
Clara Metcalf Goodman, who encouraged my pursuit of biology in
general and snakes in particular.

ACKNOWLEDGEMENTS
I gratefully acknowledge the help of the many individuals who
contributed to this study. I especially thank Drs. Archie F. Carr,
Brian K. McNab, Frank G. Nordlie, and E. S. Ford for their assistance
in procurement of equipment, and invaluable comments on the manuscript.
I thank Dr. Paul Byvoet and Mr. Ralph Carroll for their technical aid.
I am indebted to Ms. Debbie Bee, Ms. Marion Edwards, Ms. Martha
Johnston and Mr. Craig Parenteau for aid in data collection and to
Mr. Porter Reed for helping me reclaim my experimental pen from the
depths of Lake Alice after heavy rains.
I also thank Ms. Jill Jordan for proofreading the manuscript,
assistance in drawing figures, collection of data, and mind-boggling
assessments of my data. I profited from the useful counsel of Ms. Peg
Estey in the preparation of illustrative material.
Finally, my thanks to Ms. Donna Gillis for typing this manuscript
and for removing many of the bureaucratic barricades to completion of
my degree.
iii

TABLE OF CONTENTS
Page
ACKNOWLEDGEMENTS iii
LIST OF TABLES vi
LIST OF FIGURES vii
ABSTRACT • • • ix
INTRODUCTION 1
MATERIALS AND METHODS 3
Collection and Maintenance of Specimens 3
Radio Telemetry 4
Experimental Apparatus 4
Thermal Gradient 13
Metabolism 14
Digestive Efficiency 15
RESULTS AND DISCUSSION 17
Preferred Body Temperature 17
Behavioral Thermoregulation 30
Morning Emergence 30
Effect of air and water temperatures 30
Effect of acclimation 38
Effect of physiological state 41
Effect of light 41
Temporal changes in emergence response 44
Maintenance of Preferred Body Temperature 45
Evening Submergence , 47
iv

Factors Affecting Preferred Body Temperature 52
Digestion 53
Other Factors 59
Ecological Significance of Reptilian PBT 62
SUMMARY 78
LIST OF REFERENCES 80
BIOGRAPHICAL SKETCH 85
v

LIST OF TABLES
Table Page
1 The preferred ranges of body temperature of freshly
caught Natrix taxispilota 26
2 Effect of digestion on normal range of preferred
body temperatures 58
3 Data for points plotted in Figure 19 for primary
heliothermic lizards 69
4 Data for points plotted in Figure 21 for nocturnal
reptiles 75
5 Data for points plotted in Figure 21 for diurnal
snakes and forest lizards
76

LIST OF FIGURES
Figure Page
1 X-ray photograph of a Natrix taxispilota with an
ingestible radio transmitter in its stomach 6
2 Experimental pen at Lake Alice ...... 9
3 Experimental chamber used to determine the responses
of water snakes to various combinations of air and
water temperature 12
4 Effect of acclimation temperature on the range of body
temperatures selected by Natrix taxispilota in a
gradient ^9
5 Natrix taxispilota body temperatures and associated
air temperatures at Neman's Lake during December
and January 21
6 Natrix taxispilota body temperatures and associated
air temperatures at Newnan's Lake during March .... 22
7 Body temperature of Natrix taxispilota collected at
Newnan's Lake between 1130 and 1600 hours from March
through October ..... 25
8 Metabolic rate of Natrix taxispilota as a function of
acclimation temperature and body weight ....... 29
9 Behavioral responses of a 554 g Natrix taxispilota to
combinations of air and water temperature from 5°C
through 35°C ..................... 31
10 Body temperatures of Natrix taxispilota and associated
air temperatures at time of capture at Newnan's
Lake 35
11 Average body-air temperature differentials of Natrix
taxispilota at Newnan's Lake as a function of air
temperature 37
12 Number of Natrix taxispilota basking on various days
throughout the year 40
13 Number of Natrix taxispilota basking at various
times on April 9, 1970 43
vii

14 The relationship between body size and body-air
temperature differentials of Natrix taxispilota ... 49
15 Changes in body temperature of a Natrix taxispilota
thermoregulating under natural climatic
conditions . 51
16 Four-day body temperature record of a Natrix
taxispilota digesting a fish 55
17 The effect of temperature on digestive extraction
efficiency of Natrix taxispilota 57
18 The relationship between preferred body temperature
and critical thermal maximum in reptiles 65
19 Relationship between preferred body temperature of
primary heliotherms and the highest air temperature
recorded in their collection area 68
20 Effect of temperature on the metabolic rate of a 509 g
Natrix taxispilota 72
21Relationship between reptilian preferred body temperature
and highest air temperature recorded in their collection
area 74
viii

Abstract of Dissertation Presented to the Graduate Council
of the University of Florida in Partial Fulfillment of
the Requirements for the Degree of Doctor of Philosophy
THERMOREGULATION IN THE BROWN WATER SNAKE, NATRIX TAXISPILOTA,
WITH DISCUSSION OF THE ECOLOGICAL SIGNIFICANCE OF
THERMAL PREFERENDA IN THE ORDER SQUAMATA
By
Donald Eugene Goodman
June, 1971
Chairman: Dr. A. F. Carr, Jr.
Co-Chairman: Dr. B. K. McNab
Major Department: Zoology
Thermoregulatory behavior of the brown water snake, Natrix taxispilota,
was studied under natural and laboratory conditions. During daylight hours,snak
move among shade, sun, and water to maintain their preferred body tempera¬
ture. In the evening they submerge regardless of air-water temperature
differential and spend the night in the water. There are minimal thermal
thresholds for morning emergence and these levels are affected by thermal
acclimation and physiological state of the animal.
The preferred range of body temperatures of this species decreases
with increasing acclimation temperature. When digesting food, snakes
thermoregulate within a sub-range of the normal preferred range and
digestive extraction efficiency is greatest at this level -- about 30°C.
It is suggested that high thermal extremes are selective forces which
directly fix the critical thermal maximum of reptiles and indirectly fix
the preferred body temperature. The relatively low thermal preferenda of
snakes may be a function of their lack of limbs which precludes thermo¬
regulation with the degree of independence of conductive heat exchange with
the substrate characteristic of lizards.

INTRODUCTION
Many species of reptiles utilize solar radiation to attain body
temperatures greatly in excess of ambient temperatures. Some species
have an extensive behavioral repertoire which enables them to regulate
their body temperature within fairly narrow limits. Since these initial
discoveries were reported (Cowles and Bogert, 1944), scores of papers
have appeared documenting such behavior for other reptilian species,
and it now seems obvious that thermoregulation is a general feature of
reptilian behavior. While some reptiles possess physiological mechanisms
that contribute to thermal homeostasis (Lueth, 1941; Cole, 1943; Cowles,
1958; Ruibal, 1961; Bartholomew and Tucker, 1963; Heath, 1965;
Hutchison ej: al., 1966; Kour and Hutchison, 1970; Weathers, 1970),
it is behavioral utilization, directly or indirectly, of solar
radiation that permits the attainment of high preferred thermal levels.
The contribution of metabolic heat to maintenance of thermal homeostasis
is negligible (Lueth, 1941; Cole, 1943; Mackay, 1964; Schmidt-Nielsen
and Dawson, 1964; Brattstrom, 1965) even in large reptiles.
With few exceptions, these studies have dealt with lizards, and
very little information exists for other reptilian groups. The few
studies of thermoregulation involving snakes (Cowles and Bogert, 1944;
Carpenter, 1956; Fitch, 1956, 1965; Brattstrom, 1965; Stewart, 1965;
Myres and Eells, 1968; Kitchell, 1969; McGinnis and Moore, 1969;
Osgood, 1970) indicate that snakes differ from lizards in their thermal
behavior. They seem to have lower thermal preferenda and to regulate
less precisely. Some workers (Cowles and Bogert, 1944; Schmidt-Nielsen
1

2
and Dawson, 1964) believe these differences are correlated with differences
in the ecology of the two groups. Most snakes, for instance, are nocturnal
or crepuscular and many are fossorial; lizards are mostly diurnally active
and terrestrial. Even among nocturnal and fossorial reptiles, however,
basking in the sun has been either regularly or occasionally reported
(Cowles and Bogert, 1944; Bailey, 1949; Brattstrom, 1952). The signi¬
ficance of diurnal thermoregulation in such forms has never been explored.
This study was undertaken to determine the significance of thermo¬
regulation in a species of snake which is both semi-aquatic and
nocturnally active. Natrix taxispilota, the brown water snake, spends
nights in the water of large open lakes or rivers and springs. During
the daylight hours of the warmer months, the species commonly lies on
limbs overhanging the water, either in the sun or in the shade. Except
for reproductive behavior in the early spring, little activity occurs
during the day. This snake almost never occurs away from the water's
edge, and the aerial phase of its existence is limited to basking on
vegetation, rather than shore. While lying above the water, the snake
is surrounded by a thermal medium that is virtually homogeneous, and
heat exchange is largely radiative. Convective heat exchange there
is minimal because snakes remain in the water on windy days. Heat
exchange during the aquatic stage of the activity cycle, however,is
almost completely conductive. Because the species' activity is
partitioned almost completely between these two phases -- nocturnal
aquatic activity and diurnal arboreal basking -- it seems an ideal
snake for a study of the mechanisms and significance of thermo¬
regulation.

MATERIALS AND METHODS
Collection and Maintenance of Specimens
Almost all the snakes used for this study were collected at
Newnan's Lake, 8.7 km east of Gainesville, Alachua County, Florida.
This 2390 hectare lake has a mean depth of two m and is bordered by
trees, particularly pond cypress Taxodium ascendensand water ash
Fraxinus caroliniana, both of which extend from the shoreline out for
as much as 20 m into the lake. It is at the interface of the lake
and the outermost trees that most of the Matrix taxispilota were found
basking. Animals used in laboratory studies were collected by hand
from a motorboat. Cloacal temperature was recorded at this time with
either a Schultheis thermometer or the thermister probe of a YSI
six-channel tele-thermometer. Air temperature was taken in the shade
at the time of capture and water temperature was recorded at the surface
and at a depth of 2/3 m. A black-bulb temperature was recorded in direct
sunlight with a mercury thermometer, the bulb of which had been coated
with flat black paint.
A 1.12 km section of shoreline was used as a census area and, at
irregular intervals, the number of snakes basking in the trees of this
area was recorded. These surveys were always conducted between 1300 and
1500 hours EST. On a few days, censuses for this and other areas were
taken at hourly intervals betx^een 0700 and 1830 hours EST to determine
the extent of temporal variation in the number of basking individuals.
Associated air, water, and black-bulb temperatures were recorded during
censusing, and general weather conditions were noted.
3

4
Snakes used for thermal gradient, digestive efficiency, and metabolic
experiments were acclimated prior to use. Each animal was housed in a
plastic storage container with holes in the removable lid. These containers
were placed in a Jewett environmental cabinet, a Forma model 13 incubator,
or a Lab Line controlled environmental room where the temperature was main¬
tained within .5°C. All snakes received 12 hours of light daily (0900-
2100 hours EST) and had water continuously available in dishes which were
too small to permit submergence of snakes weighing more than 100 g.
Radio Telemetry
Ingestible blocking oscillator radio transmitters were used to
obtain snake body temperatures under experimental conditions. The
broadcast frequency used was low enough (500-1000 kc) to permit the re¬
ception of both aerial and underwater signals generated within 2 m of
the receiver, an AM-FM portable radio. Antennal loops were always
necessary tu relay the signal to the receiver.
Each cylindrical (radius =7.5 mm, length = 57 mm) transmitter was
powered by a replaceable 1.5 volt silver oxide hearing aid battery and
was waterproofed with a thin coat of 1:1 mixture of beeswax and
paraffin. The transmitter was lubricated, forced into the throat of
the snake and massaged by hand to the stomach (Fig. 1). The transmitter
was regurgitated in four or more days depending on temperature. Trans¬
mitters were calibrated immediately before and after use.
Experimental Apparatus
To study the fluctuations of body temperatures with changing
environmental temperatures, an experimental pen was built at another
nearby location, Lake Alice. This 24-hectare lake is located on the
University of Florida campus. The pen consisted of a circular galvanized -
steel cattle watering trough 2.44 m in diameter and 61 cm high. Concrete

Figure 1.
X-ray photograph of a Natrix taxispilota with
an ingestible radio transmitter in its stomach.


7
blocks were stacked in the center of the trough to a level of about 50 cm
and a wooden cable spool 76 cm in diameter was placed on its side atop
the blocks. An antennal loop system was installed so that radio trans¬
mitter signals could be monitored at a distance from the pen. This
consisted of a 25-m section of insulated copper cable ringing the
pen in three perpendicular planes. Two loops, therefore, passed under
and over the spool and their components extending above the rim of the
pen were supported by arched sections of screen moulding (Fig. 2); the
third loop was situated along the inside periphery at the rim. The
ends of this antennal loop were connected to a 20-m section of insulated
copper wire which was connected by insulated tip plugs to the antenna
of a portable AM-ET1 radio. Signals generated anywhere inside the loop
could thus be monitored many meters away. A 1/4-inch mesh hardware
cloth retaining fence was attached to the top edge of the trough and
directed inward toward the center of the pen to prevent the escape of
snakes. This apparatus was floated into the lake and filled with water
to the level of the bottom of the wooden spool. The free-floating pen
was then anchored and the wire connecting the antennal loop to the
radio was sunk to the bottom between the pen and the shore. Snakes
used in this phase of research were introduced into the pen and allowed
several days to adjust to their environment. They were then force-fed
an ingestible transmitter. On sunny days, the snake had both sunny
and shaded basking sites available on the wooden spool, or it could
remain underwater in the cavities of the concrete blocks. Air, water,
and black-bulb temperatures were monitored with either a YSI tele¬
thermometer located on shore or with mercury bulb thermometers. In
trial determinations, the water temperature inside and outside the pen
never differed by more than 1.5°C. The water inside was sometimes

Figure 2.
Experimental pen at Lake Alice.

9

10
slightly cooler, presumably because of the shade provided by the vertical
sides of the pen. Observations were made from the shore either with the
naked eye or through 30 X binoculars, depending upon the distance
separating the observer and the pen.
A laboratory apparatus was used to study thermoregulatory behavior
under more controlled conditions. A 230 liter aquarium was made by
sealing a refrigerator liner, cutting a large window in one side and
sealing in a section of reinforced glass. Water temperature was con¬
trolled by circulating water between the aquarium and a Forma constant
temperature water bath. A bottomless wood-frame 1/4-inch mesh cage
(90 cm X 70 cm X 40 cm) with sliding glass panels in front, was placed
above the aquarium, and Sambucus limbs were wired into positions both
underwater and above water to provide the snakes with numerous resting
and basking sites. A 250 watt infrared heat lamp was placed directly
above the right side of the cage about 20 cm above the highest basking
site. A wooden partition was hung from the top of the cage; this did
not restrict movement but rather shaded the left side of the cage from
"sunlight" (Fig. 3). Caged animals could thus either remain submerged
or bask aerially in the "sun" or shade. This aquarium-cage-water bath
combination was placed inside a Lab Line controlled environmental room
which maintains temperatures between -20 and 70°C within .5°C. Water,
air and black-bulb temperatures were monitored with a YSI tele-thermometer
placed outside the room. The probes were placed inside the aquarium pen
in the water, shaded air and approximately 20 cm directly below the
sunlamp respectively. The black-bulb probe was coated with flat black
paint. Ingestible transmitters were used to monitor body temperatures.
A three-plane antennal loop was placed in the aquarium cage and leads
were extended outside the room to the antenna of an AM-FM radio. All

Figure 3.
Experimental chamber used to determine the
responses of water snakes to various combinations
of air and water temperature.

12

observations were made through two 10 cm X 6 cm holes in a sheet of
brown paper which covered the glass door of the environmental room.
With this apparatus, air and water temperatures could be monitored and
varied independently, the snake's behavioral adjustments could be
observed and its body temperature recorded without disturbing the
animal.
Responses of the animals were recorded for all combinations of
air and water temperatures from 5° through 35°C. A timer was attached to
the environmental room and a 12-hour light cycle (0900-2100 hours EST)
was used throughout. Because of the nature of the transmitter used,
it was difficult to separate two signals; consequently one animal,
a 554 g female, was used for all determinations. Numerous individuals
were later run at selected temperature combinations to verify the
generality of responses of this individual. The female used in this
experiment was not acclimated to any particular temperature because
reacclimation after each run would have prolonged the experiment by
many months. Also, the temperature combination changes were never
drastic. Usually the water temperature remained constant while all
air temperatures from 5°C through 35°C were run. Each combination was
run for two hours and then the air temperature was elevated 2°C. Since
these temperature changes were gradual, there is no reason to believe
that the snakes used in this experiment were acclimated to temperatures
to which they would not ordinarily be acclimated under the same thermal
conditions in the wild.
Thermal Gradient
A thermal gradient was used to determine preferred body temperature
levels in this species. The gradient consisted of a rectangular open-
top wooden box 3.35 mm long, 30 cm wide and 30 cm high with a nickle-steel

14
alloy floor. The front of the box was marked at 5 cm intervals from the
hot to the cool end. At the cool end, a bottomless one-gallon aluminum can
was cemented to the floor of the gradient and filled 2/3 full of x^ater.
Cold water was then circulated through a coiled section of copper tubing
in the can. Heat was provided at the other end by an electric iron that
was placed flat on the metal floor. A 500 ml beaker of water was placed
beside the iron to maintain a high humidity inside the gradient. Panes
of glass were placed on top of the gradient to prevent escape of snakes
and to permit observation. A gradient with an average AT of 1°C per
30 cm between 20° and 34°C could be maintained indefinitely after an
initial eight hour warm-up period. Acclimated snakes were force-fed
ingestible transmitters at about 2100 hours, placed in the gradient,
and left overnight for adjustment. Body temperature and location in
the gradient were recorded at approximately 1-1/2 hour intervals between
0900 and 2400 hours of the following day. Snakes in the gradient re¬
ceived the same 12 hour photoperiod from overhead lighting as in their
acclimation quarters. A red light was used when readings were taken
during hours of darkness.
Metabolism
Metabolic rates were measured with a Beckman G-2 oxygen analyzer.
Metabolic chambers consisted of 21.5 cm diameter glass battery jars
30.5 cm high, with holes drilled at low and high levels on the sides
to let air in and out. A plexiglass lid with a 9.0 cm diameter hole
for a size 15 rubber stopper was cemented to the top of the chamber.
Acclimated snakes were introduced .into the chamber which was then
submerged in a controlled-temperature water-bath that maintained water
temperature within .5°C. Air xras pumped through a coil of copper
tubing that was submerged in the water bath before entering the chamber.

15
Oxygen consumption readings were taken at half-hour intervals until
stable values were obtained.
Digestive Efficiency
The effect of temperature upon digestive efficiency was measured
calorimetrically. A large number of gizzard shad, Dorosoma cepedianum,
were collected by rotenone poisoning at Newnan's Lake, and immediately
frozen. In feeding experiments, fish were weighed, ground whole in a
Waring blender and freeze-dried in a Virtis freeze-drying apparatus.
The resulting mixture was ground again and filtered through 1/4-inch
mesh screening to remove scales and large scale fragments. The re¬
sulting powder was thoroughly mixed and a .5 to 1.0 g sample removed
for calorimetric determination in a Parr adiabatic oxygen bomb calori¬
meter. The remaining powder was rehydrated to the original wet weight
calorimetric value and immediately fed to preweighed acclimated snakes
at a level of .1 g per g of body weight. The food was massaged by
hand to the snake1s stomach and animals were then replaced in acclimation
quarters and permitted to digest the meal at the temperature to which
they were acclimated.
Cages were checked daily for defecation and the feces were rinsed
out of the cages, collected in individual beakers and refrigerated.
After digestion was completed (the cessation of defecation) the
accumulated feces were either freeze-dried or vacuum dessicated and
the dry feces weighed and bombed. At the temperatures of 20°C and
above, snakes passed musk from the musk glands, the amount increasing
with temperature. The quantity of musk per g of body weight was
determined at the acclimation temperatures used and samples were
bombed to determine calorimetric value. A correction for this factor
was introduced into the calculations. Digestive efficiency is defined

16
here as:
Of “ Qn
E = 1 * —
where E = digestive efficiency; Cf = caloric value of feces; =
caloric value of ingested food; and = caloric value of musk. Dried
samples of fish, feces, and musk were weighed to the nearest .0001
gram on a Mettler H15 balance.

RESULTS AND DISCUSSION
Preferred Body Temperature
Throughout this discussion, the term preferred body temperature
(abbreviated PBT) will be used in accordance with Peters (1964) who
defined it as "that temperature at or about which all members of a
reptilian species will maintain themselves given the opportunity to
select proper substrate, exposure to sunlight, or other thermal factors."
The PBT can thus refer to a thermal range, as initially defined (Cowles
and Bogert, 1944) or to the mean of that range, the latter being more
useful for comparisons of interspecific preferences.
The level of body temperature selected by Natrix taxispilota in a
thermal gradient is inversely proportional to the temperature at which
the snakes were acclimated (Fig. 4). This is consistent with the find¬
ings of Wilhoft and Anderson (1960) for Sceloporus occidentalis. The
ecological significance of such interdependence is not immediately clear.
It might be expected that PBT would be independent of acclimation as
Licht (1968) found in Anolis, and serve as an immutable focal point for
thermoregulatory behavior. In other vertebrate poikilotherms, similarly
disparate results have been obtained. Rana pipiens tadpoles (Lucas and
Reynolds, 1967) and many fish (Norris, 1963; Fry, 1964) show changes in
PBT with acclimation, but the preferred thermal level of the newt
Tari.cha rivularis cannot be shifted by acclimation (Licht and Brown,
1967). Thus, it is impossible to generalize about the capacity of
vertebrate poikilotherms for adjustment of their thermal preferenda.
17

Figure 4.
Effect of acclimation temperature on the
range of body temperatures selected by
Natrix taxispilota in a gradient.


20
Especially puzzling is the fact that the relationship in Natrix
taxispilota is inverse, because the critical thermal maximum is directly
correlated with the acclimation temperature (Lowe and Vance, 1955; Larson,
1961; Bradshaw, 1965; Kour and Hutchison, 1970) and PBT, at least in
interspecific comparisons, is directly proportional to critical thermal
maximum (Brattstrom, 1965; see Fig. 18). These inconsistencies warrant
an examination of the ecological significance of the physiological capacity
for thermal acclimation in these snakes.
Hiere is some evidence that seasonal acclimation of PBT does occur
in temperate zone reptiles. Mueller (1969) found that both PBT (measured
in a gradient) and critical thermal maximum were higher in Sceloporus
graciosus collected in the summer than in those collected in the spring.
Similar increases in the level of field body temperatures from spring to
summer have been found in two garter snakes, Thamnophis sirtalis and T.
butleri (Carpenter, 1956), and in two lizards, Cnemidophorus sexlineatus
and Sceloporus woodi (Bogert, 1949), A similar seasonal variation was
found in body temperatures of Natrix taxispilota, but the differences
were not consistent with the laboratory evidence for the relationship
between acclimation temperature and PBT. The level of body temperature
in December and early January ranged between 14 and 20°C and most values
were below air temperatures (Fig. 5). By late January, higher air
temperatures resulted in body temperatures of 22.5 to 26°C with values
approximating air temperature. In March, most body temperatures ranged
between 26 and 30°C (Fig. 6) and exceeded air temperature. These
observations were made on sunny and relatively windless days when black-
bulb temperatures exceeded air temperatures by 4 to 10°C. The occurrence
of snake body temperatures below air temperature can be explained only
as resulting from recent emergence from cooler water and initial evaporative

21
Figure 5. Natrix taxispilota body temperatures and
associated air temperatures at Neman's
Lake during (A) late December and early
January and (B) late January.

22
AIR TEMPERATURE (°C)
Figure 6. Matrix taxispilota body temperatures and
associated air temperatures at Newnan's
Lake during March.

23
cooling. Throughout the warmer months, body temperatures remained
approximately within the range found in March (Fig. 7), but by mid-
October, lower air temperatures again caused a decrease in the field
body temperatures. Thus, field data provided no evidence of the inverse
relationship that might be expected between seasonal temperature (and
presumably thermal acclimation of PBT) and level of body temperature.
However, these field values for winter represent, at best, levels
of temperature attainable and not necessarily those preferred. Snakes
collected in January selected warmer temperatures in a gradient than those
collected in April or July (Table 1), suggesting that acclimation of
PBT does occur in nature. The body temperatures selected by snakes
collected in April and July did not differ significantly, indicating
that these snakes were acclimated to a common thermal level, their PBT.
During the colder weather of January, however, thermoregulatory behavior
ceased and the snakes became acclimated to the colder thermal regime of
the water in which they remained torpid. Their PBT at this time re¬
flected this acclimation.
Metabolic data also suggest this relationship. Figure 8 gives
the metabolic rate of snakes as a function of size and acclimation
temperature. The level of metabolism at a given temperature is in¬
versely correlated with acclimation temperature. This relationship has
been reported for fish, amphibians, reptiles and many invertebrates (for
extensive reviews, see Berg, 1953; Bullock, 1955; Fry, 1958) and appears
to be a nearly universal characteristic of poikilotherms. When snakes
were maintained at varying thermal regimes (30°C from 0901 hours
through 2100 hours, 20°C from 2101 hours through 0900 hours), however,
their metabolism became acclimated to the higher of the two temperatures
(Fig. 8). Acclimation to the highest of varying temperatures has been

Figure 7.
Body temperatures of Matrix taxispilota
collected at Newnan's Lake between 1130-
1600 hours from March through October.

NUMBER OF RECORDS
26 28 30 32
TEMPERATURE (°C)
22
24
34
K>

26
Table 1. The preferred ranges of body temperature of
freshly caught Natrix taxispilota.
JANUARY
APRIL
JULY
PBT RANGE (°C)
29.4-33.5
25.3-30.9
25.2-31.1
MEAN
31.6*
27.9
28.2
N (OBS.)
3 (37)
3 (38)
4 (47)
’'Differences between means for April and July are not
statistically significant but the mean for January
differs significantly (p- 0.05) from the other means.

27
reported for Rana pipiens (Hutchison and Ferranca, 1970) and for several
species of fish in both the field (Brett, 1944) and under controlled
conditions (Fry et al., 1946; Heath, 1963). These data suggest that a
poikilothermal animal can acclimate the level of its metabolism by
thermoregulatory behavior. Only when the environmental temperature
becomes too cold to permit thermoregulation at the preferred level
would there occur acclimation of body functions to a non-PBT level.
There is, then, a seasonal variation in PBT of Natrix taxispilota.
It appears that the level at which body temperature is maintained sets
the acclimation temperature, and the level of thermal acclimation in
turn affects the PBT. The range of body temperatures found in Natrix
taxispilota during March through October (23-32°C) correlates almost
exactly with those preferred (23.9-33.1°C) by snakes acclimated to
25°C and 30°C -- a close agreement between field and laboratory data.
Thermoregulacion at the preferred level apparently fixes the level
of thermal acclimation throughout those parts of the year.when adequate
thermal opportunities exist. During the colder months, when this is
not possible (Fig. 5), the level of body temperature, and presumably
thermal acclimation, varies with water temperature.
The inverse relationship between acclimation temperature and
PBT probably represents an overcompensation mechanism which is of
value during periods of thermal extremes. It is unlikely that cold-
acclimated snakes in nature could ever attain the body temperatures
selected by cold-acclimated individuals in a gradient. But by be-
haviorally thermoregulating in such a manner as to attain these high
levels, snakes may significantly elevate their body temperatures.
The lower levels preferred by warm-acclimated snakes probably reflect
a mechanism that is of importance only in an evolutionary sense. The

Figure 8.
Metabolic rate of Matrix taxispilota as a
function of acclimation temperature and
body weight.
A. acclimated to 20°C, B. 25°C, C. 30°C,
D. 35°C, E. varying temperatures (20°C
night, 30°C day).

29
LOG BODY WEIGHT (g)

30
highest air temperature recorded in Gainesville in a 40 year period
(Kincer, 1941) is 39.4°C which is several degrees below the probable
critical thermal maximum for Natrix taxispilota (Brattstrom, 1965).
Only when drastic climatic warming occurs would snakes become acclimated
to temperatures significantly above their preferred range and there
would be a clear selective pressure favoring individuals who behavior-
ally sought cool body temperatures even if the lowest attainable body
temperature was above the preferred level.
Behavioral Thermoregulation
»
Morning Emergence
*
Brown water snakes almost invariably spend the night in the water.
Hie time of emergence depends upon several climatic factors and upon
some endogenous responses of the snake.
The effect of air and water temperatures on emergence
Figure 9 shows the response of a 554 g female water snake main¬
tained in the environmental chamber to all combinations of air and water
temperatures between 5 and 35°C. This includes all the thermal regimes
which the species ever encounters in nature and several artificial situ¬
ations. The responses of several other animals to a number of these
thermal combinations never differed appreciably from those of the
554 g female so the pattern shown in Figure 9 may therefore be con¬
sidered representative. It should be remembered throughout the
discussion that animals used in this laboratory experiment were adapted
to the approximate thermal combinations to which their responses were
recorded (see Materials and Methods).
The lowest air temperature that elicited emergence was 16°C and
then only if the water temperature was 21°C or above. This latter
combination is an artificial situation at one extreme of a general

31
Figure 9. Behavioral responses of a 554 g Natrix taxispilota
to combinations of air and water temperature from
5°C through 35°C.
snake
snake
â–¡ snake
in water
in sun
in shade

32
pattern; the colder the water temperature, the warmer the air
temperature needed to elicit emergence. The lowest water temperature
at which snakes emerged was 10°C and then only if air temperature
was at least 25°C (again an artificial situation). There are,
therefore, lower limits for air and water temperatures that
elicit emergence in Natrix taxispilota and above these extremes,
these minimal values are inversely related. 'This inverse relation¬
ship is not isothermal -- i.e. the slope of this air-water temperature
interface is not -1.0.
At a water temperature of 18°C, snakes will emerge for a minimal
air temperature of 18°C, but at water temperatures below this level
air temperatures must exceed water temperature to evoke emergence
(Fig. 9). The lower the water temperature, the greater the air-water
temperature differential required for emergence. Values for this
differential at or near the water temperature asymptote of 10°C are,
as mentioned, not ecologically significant because such differentials
do not occur in nature.
At water temperatures above the air-water isothermal emergence
point (18°C), the minimal water temperatures that evoked emergence
were in excess of air temperature. The higher the water temperature,
from which a snake emerges, the higher its body temperature at
emergence and the less time it takes a basking individual to reach
the preferred thermal level. This may explain why snakes emerge
from warm water into cooler air at water temperature above 18°C.
Although the water is relatively warm, it is still below the preferred
level. Basking permits attainment of PBT, or at least a closer
approximation than is represented by the water temperature. Thus,
snakes apparently will not emerge when their body temperatures are

33
below 18°C unless the aerial phase insures rapid attainment of this
level.
Figure 10 summarizes the field relationship between air and
body temperature. It is significant that only 5 percent of the body
temperature records are below 18°C, a close agreement with laboratory
results. The decrease in number of records for snake body temperature
at air temperatures below 18°C is precipitous and not a gradual attenu¬
ation. The body-air differentials maintained by snakes at air
temperatures from 18°C through 30°C are inversely correlated with
air temperature (Fig. 11). This is clearly a reflection of differential
utilization of sunlight as a function of environmental temperatures.
It is ecologically significant that there exists a lower thermal
threshold for thermophilic responses as evidenced by the refusal of
snakes to emerge at water (and therefore body) temperatures below
10°C even when air temperature was warmer. Below the body temperature
required for coordinated locomotion, emergent snakes would be very
vulnerable to predation by homoiotherms. Also, at temperatures below
the threshholds for feeding and digestion, thermophilic responses
would increase the metabolic maintenance cost without providing
additional energy sources. This would deplete the reptile's energy
stores needed for periods of torpor and (at higher latitudes) hiber¬
nation .
When the water temperature approached the lower limit of the
preferred range (25°C), a common occurrence between April and October,
the minimal air temperature required to evoke emergence increased
sharply from 17°C at 24°C water temperature to 23°C at 25°C water
temperature (Fig. 9). At water temperatures above 25°C, the minimal
air temperatures necessary for emergence were inversely proportional

Figure 10. Body temperatures of Natrix taxispilota and
associated air temperatures at time of capture
at Nevaran's Lake.

AIR TEMPERATURE (°C)
BODY TEMPERATURE (°C)
32-|

Figure 11. Average body-air temperature differentials of
Natrix taxispilota at Newnan's Lake as a
function of air temperature. Data are the
same as those plotted in Figure 10. Numbers
in parentheses indicate number of snakes in
each category.

<
20.1-22
(20)
1
1
t
!
(25)
1 (13)
1
P 1
I
i M
1
J
22.1-24 24.1-26 26-1-28
AIR TEMPERATURE (°C)
18.1-20
28.1-30

38
to water temperatures. This sharp increase in the minimal air temper¬
atures necessary to elicit emergence suggests that water is of con¬
siderable importance for thermoregulation between April and October
when such thermal conditions are common. When water temperatures
exceeded the PBT, emergence into lower air temperatures permitted
cooling to the preferred level. These water-air temperature differen¬
tials probably never obtain in nature, and ordinarily water tempera¬
tures appreciably above air temperature would occur in the evening
well after the emergence period.
The effect of acclimation on emergence
Animals used in the environmental room studies were adapted to
the air-water temperature combinations to which their responses are
graphed in Fig. 9. In the wild, this is not always the case. Sudden
climatic changes may result in exposure of snakes to a thermal environ¬
ment to which they are not physiologically adapted. For instance,
the same approximate air and water temperature ranges on February 20,
1971 and April 16, 1970 resulted in the emergence of 118 and 25 snakes
respectively (Fig. 12). Both days were relatively humid and windless
so the disparity seems to be a reflection of the difference in climatic
conditions during the week preceeding these dates. April 16 was warm
and typical of the weather of this period, and snakes were physio¬
logically acclimated to their PBT. February 20, however, was the
warmest day of a four day warming trend. Night air temperatures had
been at or near freezing until February 18. These snakes, then, were
acclimated to temperatures well below those of February 20 and the
basking response was greatly accentuated. These data and the re¬
lationship between acclimation temperature and PBT suggest that the
minimal air and water temperature combinations required to elicit emergence
and basking are lower in cold than in warm-acclimated snakes.

Figure 12. Number of Natrix taxispilota (bars) basking
at Newnan's Lake on various days throughout
the year (summation of data from 1969, 1970
and 1971) and the ranges of air temperature
(vertical lines) recorded at the Gainesville
weather station for those days.

NUMBER OF SNAKE
AIR TEMPERATURE RANGE (cC)

41
Effect of physiological state upon emergence
At 0920 on April 1, 1967, a snake was found basking with a body
o
temperature of 13.8 C. Corresponding air and water temperatures at
the time were 11.9°C and 13.8°C respectively. These were the lowest
body temperature and associated environmental temperatures recorded
during this study (Fig. 10). It is probably significant that this
individual had a prominent bulge from a fish it had recently eaten.
It is possible that the minimum air and water temperatures necessary
to evoke basking may be lower in snakes digesting food than in those
in a postabsorptive state. Presumably, higher body temperatures should
facilitate digestive processes in reptiles (Cowles and Bogert, 1944;
Regal, 1966).
Effect of light on emergence
Combinations of air and water temperatures ideal for basking did
not induce emergence at any hour in the absence of light. When the
sun lamp was turned on during the night, snakes basked if thermal
conditions were proper. Boyer (1965) found that turtles also
would bask in response to light at any time. During cloudy weather,
basking behavior was either diminished (i.e. fewer individuals emerged)
or emergence was delayed. Boyer, (1965) found this also to be true
for turtles. In the semiaquatic reptiles studied, therefore,
basking behavior does not appear to be an endogenous rhythm, but a
response to the proper conditions of light, water temperature, and
air temperature. The physiological state of the animal is an important
factor in determining the level of the environmental temperatures
necessary to induce emergence.
Figure 13 presents the thermal environment at Newnan's Lake on
April 9, 1970 and the emergence response of snakes. Climatic conditions

Figure 13.
The number of Natrix taxispilota basking at
Newnan's Lake at various times on April 9,
1970, and the associated air, water, and black
bulb temperatures.

NUMBER OF SNAKES
43
TEMPERATURE (°C)

44
on this day were typical of the preceding:, week so these animals were
adapted to this general thermal regime. The water temperature exceeded
air temperature until 1200 hours but a peak in basking activity
occurred earlier. Emergence appeared to be initially triggered by the
onset of lighting, and to be accentuated by the rise in black-bulb
temperature.
Temporal changes in emergence response following initial onset of light
On many days, the initial air-water temperature combination used
was below the emergence threshold. Every two hours, air temperature
was raised 2°C and responses were recorded. Under such conditions,
there occurred a temporal change in the snakes' propensity for emergénce.
Temperature combinations which would elicit emergence before about 1500
hours (EST) could not elicit initial emergence after that time. The
responses recorded in Fig. 9 were all recorded prior to 1500 hours.
The heating rate (a T . = 2°C/hr) and general warming pattern approximate
conditions occurring in the wild during winter. Under laboratory
conditions, 1500 hours occurred halfway through the "sunlight" cycle
(0900-2100 hours). In nature, six hours after sunrise would be
about 1300 hours EST during December and January. An animal initially
emerging after this time in response to threshold emergence temperatures
would begin to thermoregulate at or following the peak air temperature
of the day and would confront decreasing (and therefore sub-threshold)
air temperatures for the remainder of the day. Clearly, then, this
temporal restraint on the thermophilic emergence response is necessary
to restrict thermoregulatory activity to thermally hospitable periods.
Otherwise, extensive basking would occur at low body temperatures re¬
sulting in exposure of snakes to predation at suboptimal activity
temperatures.

45
Maintenance of Preferred Body Temperature
Elaborate behavioral adjustments permit some lizards to thermo-
regulate within very narrow limits. Desert lizards apparently have
the most elaborate behavioral repertoire, including postural adjust¬
ments (Bogert, 1949; Norris, 1953; Heath, 1965), retreat to burrows
(Cowles and Bogert, 1944; Norris, 1953; DeWitt, 1967a, 1967b; McGinnis,
1967), panting (Cole, 1943; Cowles and Bogert, 1944; Ruibal, 1961;
Kour and Hutchison, 1970), climbing (Norris, 1953; DeWitt, 1967a)
and burrowing (Cowles and Bogert, 1944; Heath, 1965) . Physiological
modifications are known in these reptiles, but are clearly of secondary
importance in thermal homeostasis. Thermoregulation in snakes has been
studied very little and available information suggests that thermal
control is not as precise, and the behavioral repertoire not as
complex, as in the case of heliothermic lizards.
Following emergence, brown water snakes basked under the sunlamp
(or lay in the shade at higher air temperatures) until a body temperature
in the preferred range was reached and thereafter moved from the "sun,"
to shade, to water in order to maintain this level. No consistent
postural or coiling adjustments were noted. Retreat to the shade
or entrance into "sunlight" usually required 5 to 15 minutes. This
slow pace is probably the result of a slow heating and cooling rate
to be expected in an animal of such bulk and the wide range of pre¬
ferred temperatures.
At water temperatures below 25°C (and appropriate air temperatures),
snakes emerged and basked in the "sunlight" until their PBT was reached
and then moved into the shade. There is a broad zone of overlap be¬
tween air temperature at which animals basked in the "sun" and those
at which they retreated to the shade. This appears to be largely a

46
reflection of the distance between the snake and the sunlamp; the
ecologic equivalent would be the directness and/or intensity of
sunlight. Similarly, there was overlap between the air temperatures
at which animals lay in the shade and those at which they entered
the water. This probably is a reflection of variation in body
temperature of the snake, from one experimental run to the next,
at the time it retreated from the "sunlight."
The lowest air temperature at which snakes retreated to shade
•was/; inversely proportional to water temperature at water temperatures
from 10°C through 18°C. Evidently, more time was required at these
low water temperatures (emergence body temperatures) for attainment
of preferred levels. This resulted in the recorded extreme of a
snake basking in the "sun" at an air temperature of 31°C following
emergence from 10°C water.
In one air-water thermal regime, snakes could be found in either
air, water, or "sun" (Fig. 9). This was between water temperatures of
approximately 23°C and 27°C and air temperatures of 23°C and 28°C.
These are evidently the only water temperatures above 10°C at which
snakes may not emerge at all. At water temperatures above this
zone, there is a decline in the realm of air temperatures at
which emergent snakes bask in the sun, a marked increase in the
shade realm, and an extinction of the shade-sun overlap zone.
When air and water temperatures exceeded the preferred level,
snakes lay in the shade. These temperature combinations rarely or
never occur in nature and the value of such behavior is not clear.
In nature, extensive movement among the shade, sunlight, and
water usually occurs only in the late fall, winter, and early spring.
Low ambient temperatures at these times necessitate such thermo¬
regulatory behavior and the sparseness of foliage permits abundant

47
access to sunlight. At such times (Fig. 13) the number of individuals
basking usually peaks in late morning and declines thereafter. There
is an individual turnover and during the afternoon, submergence rate
exceeds emergence rate resulting in a decrease in the number of bask¬
ing individuals. The first individuals to attain PBT and eventually
reenter the water are probably the smaller animals since they heat
more rapidly. Data taken on March 5 substantiate this (Fig. 14).
Between 1100 and 1300 hours, there was an inverse relationship be¬
tween size of basking individuals and the body-air temperature
differential. No such correlation existed between 0900 and 1100 hours,
indicating that time of emergence was independent of body size. Figure
15 shows the changes in body temperature of a Natrix taxispilota, and
the associated environmental temperatures under natural climatic con¬
ditions of November 28, 1970, at Lake Alice.
During the warmer months (mid-April through mid-October), such
thermoregulatory behavior is seldom necessary, because air and water
temperatures during the day are usually within the PBT of this species.
Because of the level and wide range in PBT, snakes occasionally were
found to bask in one location from time of emergence until evening
submergence. Water temperatures during these months were often within
the preferred range, and most snakes either remained in the water or
had submerged by census time (Fig. 12).
Evening Submergence
With the approach of nightfall, few if any snakes remain on basking
sites above the water (Fig. 13). In initial laboratory experiments,
where lights came on at 0900 hours and went off at 2100 hours, snakes
usually emerged within an hour of onset of lighting (given proper
thermal conditions) and submerged within the 30-minute period after

Figure 14. The relationship between body size and body-air
temperature differentials of Natrix taxispilota
collected between .1100 and 1300 hours on
March 5, 1967.

TOTAL LENGTH (cm)
BODY TEMPERATURE - AIR TEMPERATURE (°C)
61?

Figure 15
Changes in body temperature of a Natrix
taxispilota thermoregulating under natural
climatic conditions of November 28, 1970,
in experimental pen at Lake Alice.
snake in water
| [ snake in shade
snake in sun

(Do) 3Snjya3dW31

52
light was terminated. After several weeks exposure to this photoperiod,
however, snakes often entered the water an hour or more before 2100 hours.
This evening submergence appears to be a temperature-independent
response to decreased light; snakes slide into the water regardless of
the air-water temperature differential. Boyer (1965'* noted that most
basking turtles left their basking sites and submerged prior to
30 minutes before sunset, although no mention was made of air and
water temperatures at these times. Since evening submergence is
evidently common in most semiaquatic reptiles, and since it is temperature-
independent (at least in Natrix taxispilota), this response probably
represents a predator avoidance behavior. Clearly much feeding --
almost exclusively on fish -- does occur at this time, when water
temperatures permit; but little feeding behavior probably occurs below
a water temperature (and therefore body temperature) of 15°C (Lueth,
1941). Large fish could ingest small Natrix, but only alligators would
represent a substantial predation threat to brorni water snakes during the
aquatic phase of their activity cycle.
In natural situations, the water is usually warmer at night '..a
thanthe air.; It may be, therefore, that evening submergence evolved
as a thermal response and persists even in the unnatural situations to
which snakes were subjected in the laboratory.
Factors Affecting Preferred Body Temperature
As previously mentioned, there appears to be a mutually causal
relationship between the level of physiological acclimation and PBT,
resulting in a fixed preferred level of about 25-30°C throughout most
of the year. There are other ecologically relevant factors which may
alter the level of preferred temperature, at least temporarily.

53
Digestion
Snakes acclimated to 25°C were fed fish containing ingestible
transmitters and were found to regulate (in a gradient) at a warmer
end of the normal range (Table 2.). The same pattern was found in
animals that were given access to a heat lamp in an isothermal (21.0°C)
environment. Two Natrix taxispilota were fed fish containing transmitters
and permitted to thermoregulate in this environmental chamber. The level
of air and water temperatures was low enough to induce basking but high
enough to permit attainment of body temperatures in excess of 30°C
by basking under the sunlamp. The first day following feeding, these
snakes spent at least half the day in the water before emergence. This
delayed emergence is probably unrelated to thermoregulatory behavior. It
is a common behavioral trait of captive snakes, including terrestrial
species, to submerge in any available water after consuming a large
meal. The moisture evidently facilitates stretching of the skin, or
at least provides better support for the portion of the body containing
the food. Upon emergence, snakes maintained body temperatures mostly
between 27.5°C and 31cC. When they first emerged, the snakes usually
lay with the bolus directly under the sunlamp and moved to a cooler
area after body temperature reached 30°C to 32°C. A four-day thermal
record for one of these snakes is shown in Fig. 16.
Thermophilic responses to feeding have been reported for other
reptiles (Regal, 1966; Bustard, 1967; Kitchell, 1969) including two
semiaquatic snakes, Natrix sipedon and Thamnophis sirtalis. In all
cases, the preferred thermal range following feeding seems to con¬
stitute a sub-range of the postabsorptive PBT. This increase in pre¬
cision of thermoregulation has in all cases been interpreted as a
facilitation of digestive processes.

Figure 16. Four-day body temperature record of a Natrix
taxispilota digesting a fish eaten on March 23,
1971. Throughout the first day of digestion,
the snake remained in the water (see text);
the subsequent four-day period is shown. Air
and water temperature were maintained at 21°C.
Dark bars indicate periods of darkness; light
bars indicate periods of light.

ODY TEMPERATURE (°C)
32
31-
30-
29-
28-
27H
23-s
22-
21-
204-
HOUR

56
The effect of temperature on digestive efficiency was determined
for Natrix taxispilota at 20, 25, 30, and 35°C. The greatest extraction
efficiency occurred at 30°C (Fig. 17) and decreased both above and below
this temperature. This thermal level corresponds to the preferred
level for digestion (Table II). Regurgitation of food was very common
among snakes maintained at 35°C, another indication that this was
supraoptimal thermal level for digestion. Below 30°C, digestive
efficiency decreased with decreasing temperature but the 82.6 percent
efficienty level at 20°C is still a substantial figure. It is obvious
that high body temperatures expedited digestion but were not absolutely
necessary, indicating that under natural conditions, digestive processes
would continue at night well after submergence if water temperature was
not excessively cold. This wide range of digestive activity is probably
necessary in such poikilotherms to prevent putrefaction of ingested
food at night and during other periods when body temperature falls well
below 30°C. Putrefaction would be a particularly great problem in
snakes since they ingest items whole and the internal tissue of in¬
gested items would not be reached by gastric enzymes for many hours
or days if digestion ceased at temperatures slightly below the optimal
level.
The influence of temperature on gastric digestion in the European
grass snake, Natrix natrix, was studied by Skoczylas (1970) who used
x-ray photography to determine the speed of digestion at temperatures
of 5, 15, 25, and 35°C. He found that digestion was completely
arrested at 5°C and proceeded very slowly (or ended in regurgitation)
at 15°C. Digestion was complete at both 25 and 35°C but was faster
at 25°C. Digestive rates in the king snake, Lamnropeltis getulus,
were found by Root (1961) to be similar to those of N. natrix below

57
BODY TEMPERATURE (°C)
Figure 17. The effect of temperature on digestive extraction
efficiency of Natrix taxispilota. Horizontal line,
mean; vertical bar, standard deviation; vertical
line, range.

Table 2
PBT RANGE (°C)
MEAN
Effect of digestion on the normal range of
preferred body temperatures.
POSTABSORPTIVE DIGESTING
25.7 - 32.6 28.2-32.1
29.86 30.28
N (OBS.)
5 (66)
4 (49)

59
25°C, but the maximum digestive rate occurred at the highest temperature
employed, 33°C. Skoczylas attributed the discrepancy in digestive rates
of the two species at 33-35°C to intraspecific differences in PBT.
Research on digestive rates of other poikilotherms tends to substantiate
this generalization. Many freshwater fish are able to digest food at
2°C to 5°C (Wangensteen et al., 1958; Molnar and Tolg, 1962). These
temperatures are below the lower limit of the thermal activity range
of Spenodon punctatus, the lowest known for any reptile (Bogert, 1953a,
1953b). In fish studied over a wide range, digestive rate appears to
be directly correlated with water temperature (Riddle, 1909). However,
the rate of food input may also influence digestive efficiency. Davies
(1964) found that in Carassius auratus, the proper level of food input
could increase extraction efficiency to 92-94 percent at either 21.5°C
or 12°C. Other workers (Ivlev, 1939; Gerking, 1955) have found extraction
efficiencies of other fish at a given temperature to be independent of
input rate. Amphibians also show wide thermal ranges for digestion
(Pegel, 1939; Joly, 1958; Root, 1961) and are capable of digesting at
temperatures less than 10°C, levels at which peristalsis ceases in most
reptiles (Skoczylas, 1970). The processes of gastric digestion and
peristalsis may have different thermal thresholds, as in the painted
turtle, Clirysemys picta, which cannot digest, but maintains peristalsis,
at 5°C (Fox and Masacchia, 1959). Nonheliothermic poikilotherms, there¬
fore, seem to have lower thermal thresholds for digestive processes than
heliothermic species.
Other Factors Affecting Preferred Body Temperature
Regal (1967) clearly demonstrated that several species of lizards
placed in a gradient will select night temperatures that are well be¬
low their preferred diurnal PET. This was true of Klauberina riversiana,

60
a nocturnally-active lizard, as well as three heliothermic
diurnally-active forms. No such endogenous variation in the level
of PBT was found in Natrix taxispilota maintained in a gradient.
From April through October, water temperatures at the study site
were generally warmer at night than air temperatures. A voluntary
hypothermic response to darkness would therefore be inconsistent with
their behavior. Evening submergence appeared to be a temperature-
independent response to diminished light.
The data of Kitchell (1969) suggest that snakes undergoing
ecdysis actively select body temperatures below their normal PBT.
The three species he investigated included two semiaquatic species,
Thamnophis sirtalis and Natrix sipedon. The latter, when not shedding,
had a PBT of 28.03 + .28°C (mean + standard deviation) but a preference
of 18.71 + .38°C when undergoing ecdysis. In the present study, there
were not enough data available to detect such voluntary hypothermic
response to ecdysis but, in view of the unanimity of Kitchell's data
for three species of snakes -- one congeneric with N. taxispilota --
it seems likely that brown water snakes have lower thermal preferenda
when shedding.
No pregnant females were used in this study but data from several
sources suggest that such individuals have thermal preferences that
differ from those of males and non-pregnant females. Stewart (1965)
found in Thamnophis sirtalis and T. ordinoides "a consistent tendency
for pregnant females of both species to maintain relatively high body
temperatures." Fitch (1960) found that gravid female copperheads,
Ancistrodon contortrix, regulated within more precise limits than males
or non-pregnant females and noted that "most of the copperheads found
basking in sunshine in summer were females."- Osgood (1970) found

61
pregnant female Natrix taxispilota and N. fasciata to thermoregulate
within a narrower temperature range than males or non-pregnant females,
but his sample for Natrix taxispilota consisted of only four individuals
(three pregnant females, one male). In all of these accounts, the body
temperatures fell within the limits of the normal PBT but constituted
a smaller sub-range within it.
The effect of intraspecific differences in size upon PBT has been
examined by several workers, inter alia Bogert (1949), Wilhoft (1958),
Hirth (1963), and Brooks (1968). Only in Basiliscus vittatus (Mirth,
1963) were statistically significant differences found and the differences
were so slight (35.3 + 0.05°C in juveniles, 34.7 + 0.07°C in adults) that
ecological significance cannot be ascribed. The most likely candidate
for an ecologically significant change in PBT with size is probably
Varanus komodoensis, the world's largest lizard. This species is
arboreal as a juvenile and becomes terrestrial upon attaining the
length of 1.5 to 2.0 meters (Walter Auffenberg, private communication).
It would be surprising if a change in PBT did not accompany this change
in habitat preference.
The PBT in a given species of reptile, then, is not an immutable
thermal level. It may undergo temporal changes and changes reflecting
the thermal optima for various physiological processes. It has long
been known that snakes undergoing ecdysic processes refuse to feed.
This behavior pattern has been interpreted as a response to avoid
damage to the newly developing epidermal layer which would be severely
stretched or even split by the ingestion of large items. The pre¬
ceding discussion of the thermal requirements of these two processes
(ecdysis and digestion) in reptiles, suggests a thermal incompatibility
and certainly presents at least as strong an argument for their non¬
concurrence .

62
The Ecological Significance of Reptilian Preferred Body Temperature
Many workers (Ruibal, 1961; Brattstrom, 1965; Kitchell, 1969;
Skoczylas, 1970) have commented on the empirical relationship be¬
tween the PBT of reptiles and the microclimate of their habitat.
Again, these generalizations deal mostly with lizards. Diurnally-
active desert lizards generally have higher PBTs than lizards from
non-desert areas. Diurnal reptiles generally have higher thermal
preferenda than nocturnal species. Surprisingly, the significance
of this relationship has never been examined from the standpoint of
causality. Existing data on reptilian thermal preferences and tolerances
suggest that climate may be a major factor in evolutionarily setting'
the level of PBT.
The thermal extremes between which reptiles must live are the
approximate levels that freeze their tissues and those that denature
their proteins, or in other ways cause physiological heat-death. But
most, if not all, reptiles keep their body temperature from varying
with environmental temperature, by maintaining it at a certain level
within this 50°C span. Evolutionarily, reptiles can choose the ceiling
of their preferred range by behaviorally utilizing solar energy.
Empirical evidence of this is the occupation by several species of
reptiles with different PBTs of a common habitat (Cowles and Bogert,
1944; Bogert, 1959; Soule,.1963). However, the thermal characteristics
of the environment leave less evolutionary choice in the lower threshold
of the PST because reptiles lack the cooling mechanisms characteristic
of most mammals and birds (Schmidt-Nielsen and Dawson, 1964) and can
therefore cool only to the level of the coolest segment of their environ¬
ment. Summer shade temperatures in North America set this lower utilizable

o o
level at about 20 C to 23 C for diurnally-active terrestrial reptiles.
Thus, the observation that PBT is generally closer to the critical
1 2
thermal maximum than to the critical thermal minimum is to be expected,
because the thermal range between critical thermal minimum and 20-23°C
is unavailable. However, many diurnal reptiles operate at thermal
levels only a few degrees below temperatures that cause irreversible
tissue damage. The question, therefore, becomes why do not all
diurnally active reptiles choose PBTs of about 25-35°C and leave
margins of safety at both ends? The answer is apparently related to
(1) the biological effects of thermal extremes and (2) the correlation
between PBT and the critical thermal maximum.
Hypothermia slows the rates of physiological processes, but rarely
causes irreversible damage above 0°C. However, irreversible tissue
damage is incurred at temperatures above about 44°C. These temperatures
slightly exceed the highest air temperature (though certainly not the
highest black-bulb temperature) to which a diurnal animal could expect
to be exposed in its normal activity and natural habitat. There is a
direct correlation between the preferred level of body temperature and
the level of critical thermal maximum (Schmidt-Nielsen and Dawson, 1964;
Brattstrom, 1965; see Fig. 18). The highest body temperature a reptile
will ever attain must be below the CTMax if that animal is to survive,
and this body temperature should be directly related to the highest air
temperature experienced. These environmental thermal extremes are
^"The thermal point at which locomotory activity becomes dis¬
organized and the animal loses its ability to escape from conditions
that will promptly lead to its death" (Cowles and Bogert, 1944).
2
"The temperature that causes a cold narcosis and effectually
prevents locomotion" (Cowles and Bogert, 1944).

The relationship between preferred body temperature
and critical thermal maximum in reptiles (x¿ = .59)
Data are from Brattstrom (1965) for species with
sample sizes of 20+.
Figure 18.

65

66
selective factors which set the level of CTMax by eliminating the
individuals with lowest thermal tolerance. Since CTMax bears a re¬
lationship to PBT, that is apparently genetically fixed, there should
be a direct correlation between these environmental extremes and PBT.
Furthermore, the PBT of a reptile should be more strongly correlated
with the highest temperature recorded in its habitat than with any
mean high temperature value because the latter are clearly of less
evolutionary significance in fixing the level of CTMax.
2
Figure 19 shows the high correlation (r = 0.61) between PBT in
3
several primarily heliothermic species of reptiles and the highest
temperature ever recorded at the weather station nearest the collection
locality (Kincer, 1941). Studies that failed to list collecting
locality, or for which no such weather data could be found, are excluded.
Data from studies in which field body temperatures constituted the
basis for determination were included only if the sample size exceeded
20 and observational correlations were made. When these conditions
are met, PBT and mean body temperature (Peters, 1964) become synonymous
and comparison between these values is valid. The pertinent statistical
data and references are listed in Table 3.. .
As expected, the correlation with PBT is significantly greater
for maximum temperature than for the mean temperature of the hottest
month (July in the northern hemisphere, January in the southern). This
supports the hypothesis that the level of PBT is indirectly fixed
evolutionarily by its relationship to the level of CTMax, which is
directly fixed by high environmental temperature extremes. This does
3
A primary heliotherm is here defined as a diurnally-active lizard
inhabiting an open habitat (or habitats) that offer access to sunlight
throughout the day.

Figure 19.
Relationship between preferred body temperature of
primary heliotherms and the highest air temperature
recorded in the area from which they were collected.
Statistical information and sources for the data
are listed in Table 3.

PREFERRED BODY TEMPERATURE (°C)
40 4'2 4'4 46
HIGHEST AIR TEMPERATURE (°C)
36
38
4'8
50
ON
CO

69
Table 3. Data for points plotted in Figure 19 for
primary heliothermic lizards.
NUMBER IN
FIG. 19
SPECIES
N
PBT
SOURCE
1
Anolis allisoni
122
33.0
Ruibal, 1961
2
Anolis homolechis
104
31.8
Ruibal, 1961
3
Anolis sagrei
178
33.1
Ruibal, 1961
4
Crotaphytus collaris
425+
38.0
Fitch, 1956
5
Dipsosaurus dorsalis
M*
38.5
DeWitt, 1967b
6
Sauromalus obesus
49
37.7
Cowles and Bogert, 1944
7
Sceloporus graciosus
70
32.3
Mueller, 1969
8
Sceloporus occidentalis
500+
35.0
Larson, 1961
9
Sceloporus orcutti
21
35.4
Mayhew, 1963
10
Urosaurus ornatus
97
35.5
Brattstrom, 1965
11
Cnemidophorus sexlineatus
M*
39.5
Fitch, 1956
12
Sceloporus woodi
42
36.0
Bogert, 1949
13
Cnemidophorus tesselatus
33
41.3
Bogert, 1949
14
Amphibolorus barbatus
58
34.8
Lee and Badham, 1963
15
Amphibolorus inermis
M
36.8
Pianka, 1971
MAXIMUM
TEMP.
MEAN
HIGH TEMP.
CORRELATION COEFFICIENT 0.78
0.54
EQUATION
FOR LINE Y = .492X + 14.46
—
“■many

70
not mean, however, that the absolute level of PBT is solely a function
of high air temperature extremes. Any species-specific behavior
(burrowing, panting, etc.) that meliorates the severity of such
extremes will be of selective advantage. It is the interaction of
these behavior patterns and physiological tolerances that, under the
selective pressures of high temperatures, will determine the level of
PBT. Interspecific differences in behavior and physiological tolerance
will result in the utilization by several species with slightly different
PBTs of a common habitat.
By setting their body chemistry to operate optimally at a given
temperature, reptiles concomitantly- must accept diminished levels
of 'metabolic efficiency' at non-optimal temperatures. At body
temperatures below PBT, metabolism merely slows down as a function of
temperature (Fig. 20), and normal activity, such as food procurement,
ceases. But, at such times, the animal incurs no tissue damage and
the decreased level of metabolism is compatible with decreased digestive
efficiency (and therefore energy availability) and food consumption.
At temperatures above PBT, however, the decreased levels of digestive
efficiency (and metabolic efficiency generally) and food consumption
coincide wTith an increase in metabolism. In addition, very high
temperatures will cause irreversible tissue damage. So by choosing
relatively high body temperatures, heliotliermic reptiles avoid the
problem of overheating and are penalized by having to remain inactive
or suboptimally active on-cool days. The opposite strategy of choosing
a low PBT to insure more days of activity entails the risk of over¬
heating to the point of death. This, as mentioned, is probably the
mechanism that sets the level of reptilian PBT evolutionarily. High
thermal extremes will eliminate the least heat tolerant (lowest CTMax)

Figure 20. The effect of temperature on the metabolic rate
of a 509 g Natrix taxispilota at two acclimation
temperatures, (A) 20° and (B) 25°.

BODY TEMPERATURE (°C)
METABOLISM (cc02/hr)
ZL

individuals and select for a species with a higher CTMax (and PBT).
Theoretically, a reptile's CTMax should be just above the highest
ambient temperature (and body temperature) the species ever encountered
in its normal habitat during its normal period of activity. Therefore,
diurnal terrestrial species should have higher PBTs than nocturnal
terrestrial species.
Still, the highest daytime air temperature recorded in an area
should be correlated with the highest night temperature. A correlation,
then, does exist between PBT of nocturnal reptiles and highest air
temperature (Fig. 21). The correlation is weaker than with primarily
heliothermic species, as would be expected. Between the lines relating
PBT with highest air temperature in primary heliothermic species and in
nocturnal species, there are a series of points which form a third line
with an intermediate slope. The points are for diurnally-active snakes
and forest lizards. The lizards (Anolis and Eumeces) bask (in patches
of sunlight reaching the forest floor) but not nearly as extensively
as primary heliothermic species. However, the heliothermic snakes
(Coluber and Heterodon) occur in the same open habitats in which
heliothermic lizards maintain higher PBTs. This suggests that the
differences in thermal preferenda of snakes and lizards may be a
function of differences in the ecology of the two groups. The nocturnal
species used to determine line A (Fig. 21) were, with one exception
(the Gila monster, Heloderma suspectum), all snakes, so it is impossible
to determine from these data whether their lower thermal preferenda
exist because they are nocturnal or because they are snakes, or both.
One consistent characteristic of snakes that separates them from
almost all lizards suggests a basis for a lower PBT. This is the
absence of legs. The thermoregulatory significance of this is that

PREFERRED BODY TEMPERATURE (°C)
74
Figure 21. Relationship between reptilian preferred body-
temperature and the highest air temperature re¬
corded in the collection area. A. nocturnal
reptiles (circles). B. diurnal snakes and forest
lizards (squares;. C. primary heliothermic lizards
(from Figure 17). Statistical information and sources
for data are listed in Table 4 (line A) and Table 5
(line. B).

75
Table 4. Data for points plotted in Figure 21 for
nocturnal reptiles (line A).
NUMBER IN
FIG. 21
SPECIES
N
PBT
SOURCE
1
Heloderma
suspectum
57+
28.7
Bogert and del Campo, 1956
2
Elaphe obsoleta
53
28.0
Fitch, 1956
3
Thamnophis
sirtalis
157
25.6
Carpenter, 1956
4
Thamnophis
sirtalis
108
29.3
Kitchell, 1969
5
Thamnophis
sirtalis
21
29.5
Fitch, 1965
6
Thamnophis
sirtalis
M
28.0
Stewart, 1965
7
Thamnophis
ordinoides
M
27.4
Stewart, 1965
8
Thamnophis
sauritus
123
26.0
Carpenter, 1956
9
Thamnophis
butleri
54
26.1
Carpenter, 1956
10
Natrix sipedon
114
28.0
Kitchell, 1969
11
Matrix taxispilota
4S "
27.5
Present paper
12
Ancistrodon mokeson
73
27.0
Fitch, 1956, 1960
13
Crotalus cerastes
M
31.4
Cowles and Bogert, 1944
MAXIMAL
TEMP.
MEAN HIGH TEMP.
CORRELATION COEFFICIENT
0.68
0.65
EQUATION
FOR LINE
Y
= . 368X
+ 12.07
—

76
Table 5. Data for points plotted in Figure 21 for
diurnal snakes
and forest lizards (line B).
NUMBER IN
FIG. 21
SPECIES
N
PBT
SOURCE
14
Anolis allogus
148
29.2
Ruibal, 1961
15
Anolis lucius
86
29.3
Ruibal, 1961
16
Eumeces fasciatus
41+
33.0
Fitch, 1954, 1956
17
Eumeces obsoletus
M
34.0
Fitch, 1955
18
Coluber constrictor
29
30.9
Fitch, 1956
19
Coluber constrictor
127
31.5
Kitchell, 1969
20
Heterodon platyrhinos
102
31.8
Kitchell, 1969
MAXIMUM TEMP. MEAN HIGH TEMP.
CORRELATION COEFFICIENT 0.81 0.48
EQUATION FOR LINE
Y = 0.344X f 40.27

77
terrestrial snakes are in more intimate physical contact with their
environment and more vulnerable to conductive heat exchange with the
substrate. This, in part, explains why Carpenter (1956), in his
study of thermoregulation in three species of garter snakes, found
cloacal temperatures to be more closely correlated with the temperature
at the ground surface than with air temperature above or soil temperature
below. Desert lizards rely greatly on such conductive heat exchange as
a cooling mechanism. The desert iguana, Dipsosaurus dorsalis, presses
its venter from side to side in the sand exposing cooler layers to
which it loses body heat by conduction (Norris, 1953). At higher
temperatures, lizards retreat to burrows (DeWitt, 1967a, 1967b;
McGinnis, 1967; Norris, 1953) again relying on conductive heat exchange
to reach the preferred thermal level. The high surface temperatures
characteristic of desert regions frequently exceed the preferred body
temperatures of the reptiles occurring there. While a heliothermic
tetrapod can hold its body above this substrate and thermoregulate with
a degree of independence of it, snakes cannot. This undoubtedly at
least partly accounts for the paucity of diurnally active snakes in
desert areas where lizard species are abundant. And a nocturnal
activity pattern preordains a relatively low PBT.
If the absence of legs is of significance in determining the level
of PBT, diurnally-active legless lizards should fall on line B (Fig. 21)
with diurnal snakes. The only data available for such lizards «re for
the species Ophisaurus attenuatus (Fitch, 1956) in Kansas. Field
temperatures of 15 active individuals collected on clear days ranged
between 30.6°C and 33.7°C. The mean value of 32.2°C would fall 1.4°C
below the diurnal snake-forest lizard line. This is good agreement even
though this point was based on a sample size too small to warrant its
inclusion in Fig. 21.

SUMMARY
Thermoregulatoiy behavior under natural and laboratory conditions
was studied in the brown water snake Matrix taxispilota.
The effect of temperature on digestive extraction efficiency was
determined calorimetrically.
The effect of acclimation on metabolic rate and preferred body
temperature was determined.
There is an inverse relationship between preferred body temperature
and acclimation temperature in brown water snakes. A seasonal change
in preferred body temperature occurs in nature.
There is an inverse relationship between thermal level of acclimation
and metabolic rate at a given temperature. Metabolism becomes accli¬
mated to the highest of varying temperatures to which the snake is
exposed in a 24-hour period.
There are lower air and water threshold temperatures for emergence
in brown water snakes. Factors affecting the levels of these
thresholds include thermal acclimation and physiological state
of the animal.
Matrix taxispilota will not emerge at any air and water temperatures
in the absence of light.
There are temporal changes in the propensity for emergence after
initial onset of light.
Thermoregulatory responses of brown water snakes to various thermal
regimes are described and discussed.
There is a temperature-independent evening submergence response in
Matrix taxispilota.

79
11. Brown water snakes digesting food thermoregulate at a sub-level
within the normal preferred body temperature range.
12. Digestive efficiency is greatest at about 30°C and decreases above
and below this level.
13. It is suggested that high thermal extremes directly fix the critical
thermal maximum of reptiles and indirectly fix the preferred body
temperature. Supportive evidence is presented and discussed.
14. The absence of legs in snakes precludes thermoregulation with the
degree of independence of conductive heat exchange with the substrate
enjoyed by most lizards. It is suggested that this may, in part,
account for the relatively low preferred body temperatures of
snakes.

LIST OF REFERENCES
Bailey, Reeve M. 1949. Temperature tolerance of gartersnakes in
hibernation. Ecology 30: 238-242.
Bartholomew, George A. and V. A. Tucker. 1963. Control of changes in
body temperature, metabolism, and circulation by the agamid lizard,
Amphibolurus barbatus. Physiological Zoology 36: 199-218.
Berg, Kaj. 1953. The problem of respiratory acclimation. Hydro-
biologica 5: 331-350.
Bogert, Charles M. 1949. Thermoregulation in reptiles, a factor in
evolution. Evolution 3: 195-210.
Bogert, Charles M. 1953a. Body temperatures of the Tuatara under
natural conditions. Zoológica 38: 63-64.
Bogert, Charles M. 1953b. The tuatara: Why is it a lone survivor?
Hie Scientific Monthly 76: 163-170.
Bogert, Charles M. 1959. How reptiles regulate their body temperature.
Scientific American 200: 105-120.
Bogert, Charles M. and Rafael Martin del Campo. 1956. The gila monster
and its allies: the relationships, habits, and behavior of the
lizards of the family Helodermatidae. Bull. Amer. Mus. Nat. Hist.
109: 1-238.
Boyer, Don R. 1965. Ecology of the basking habit in turtles. Ecology
46: 99-118.
Bradshaw, D. 1965. The comparative ecology of lizards of the genus
Amphibolurus. Ph.D. thesis, University of Western Australia.
Brattstrom, Bayard H. 1952. Diurnal activities of a nocturnal animal.
Herpetologica 8: 61-63.
Brattstrom, Bayard H. 1965. Body temperatures of reptiles. Amer.
Midi Nat. 73: 376-422.
Brett, J. R. 1944. Some lethal temperature relations of Algonquin
Park fishes. Publ. Ontario Fish Res. Lab. 63: 1-49.
Brooks, Garnett R. 1968. Body temperatures of three lizards from
Dominica, West Indies. Herpetologica 24: 209-214.
Bullock, Theodore Holmes. 1955. Compensation for temperature in the
metabolism and activity of poikilotherms. Biological Reviews
30: 331-342.
80

81
Bustard, H. R. 1967. Activity cycle and thermoregulation in the
Australian gecko, Gehyra variegata. Copeia 1967: 753-758.
Carpenter, Charles C. 1956. Body temperatures of three species of
Thanmophis. Ecology: 372-375.
Cole, LaMont C. 1943. Experiments on toleration of high temperature in
lizards with reference to adaptive coloration. Ecology 24: 94-108.
Cowles, Raymond B. 1958. Possible origin of dermal temperature
regulation. Evolution 12: 347-357.
Cowles, Raymond B. and Charles M. Bogert. 1944. A preliminary study
of the thermal requirements of desert reptiles. Bull. Amer. Mus.
Nat. Hist. 83: 265-296.
Davies, P. M. C. 1964. The energy relations of Carassius auratus L. --
I. Food input and energy extraction efficiency at two experimental
temperatures. Comp. Biochem. Physiol. 12: 67-79.
DeWitt, Calvin B. 1967a. Behavioral thermoregulation in the desert
iguana. Science 158: 809.
DeWitt, Calvin B. 1967b. Precision of thermoregulation and its
relation to environmental factors in the desert iguana, Dipsosaurus
dorsalis. Physiol. Zool. 40: 49-66.
Fitch, Henry S. 1954. Life history and ecology of the five-lined skink,
Eumeces fasciatus. Univ. Kansas Publ., Mus. Nat. Hist., 8: 1-156.
Fitch, Henry S. 1955. Habitats and adaptations of the great plains
skink (Eumeces obsoletus). Ecol. Monog. 25: 59-83.
Fitch, Henry S. 1956. Temperature responses in free-living amphibians
and reptiles of Northeastern Kansas. Univ. Kan. Publ., Mus. Nat.
Hist., 8: 417-476.
Fitch, Henry S. 1965. An ecological study of the garter snake
Thamnophis sirtalis. Univ. Kan. Pulb., Mus. Nat. Hist., 15: 493-564.
Fitch, Henry S. i960. Autecology of the copperhead. Univ. Kan. Publ.,
Mus. Nat. Hist., 13: 85-288.
Fox, V. M. and X. J. Masacchia. 1959. Notes on the pH of the digestive
tract of Chrysemys picta. Copeia 1959: 337-339.
Fry, F. E. J. 1958. Temperature compensation. Annual Review of
Physiology 20: 207-224.
Fry, F. E. J. 1964. Animals in aquatic environments: fishes. 715-728.
In: D. B. Dill (ed.). Handbook of Physiology. Sect. 4. Adaptation
to the environment. Amer. Phy^siol. Soc., Washington, D. C.
Fry, F. E. J., J. S. Hart, and K. F. Walker. 1946. Lethal temperature
relations for a sample of young speckled trout (Salvelinus frontinalis).
Univ. Toronto Stud. Biol. 55: 9-35.

82
Gerking, S. D. 1955. Influence of rate of feeding on body composition and
protein metabolism of blue-gill sunfish. Physiological Zoology,
28: 267-282.
Heath, J. E. 1965. Temperature regulation and diurnal activity in
horned lizards. Univ. Calif. Publ. Zool. 64: 97-136.
Heath, W. G. 1963. Thermoperiodism in sea-run cutthroat trout (Salmo
clarki clarki). Science 142: 486-488.
Hirth, H. F. 1963. The ecology of two lizards on a tropical beach.
Ecological Monographs 33: 83-112.
Hutchison, Victor H., Herndon G. Dowling, and Allen Vinegar. 1966.
Thermoregulation in a brooding female Indian python, Python
molurus bivittatus. Science 151: 694-696.
Hutchison, Victor H. and Michael R. Ferrance. 1970. Thermal tolerances
of Rana pipiens acclimated to daily temperature cycles. Herpetologica
26: 1-8.
Ivlev, V. S. 1939. Balance of energy in carps. Zool. Zh. 18: 303-318.
Joly, J. 1958. Influence des basses temperatures sur cycle alimentaire
de quelques tritons Franjáis. Bull. Soc. Zool. Fr. 83: 128-131.
Kincer, J. B. 1941. Climate and weather data for the United States.
Yearbook of Agriculture: "Climate and Man." Washington, D.C.,
U.S. Gov't. Printing Office, 185-699.
Kitchell, James F. 1969. Thermophilic and thermophobic responses of
snakes in a thermal gradient. Copeia 1969: 189-191.
Kour, Edna Lynne and Victor H. Hutchison. 1970. Critical thermal
tolerances and heating and cooling rates of lizards from diverse
habitats. Copeia 1970: 219-229.
Larson, Mervin W. 1961. The critical thermal maximum of the lizard
Sceloporus £. occidentalis Baird and Girard. Herpetologica
17: 113-122.
Lee, Anthony K. and Judith A. Badham. 1963. Body temperature, activity,
and behavior of the agamid lizard, Amphibolurus barbatus. Copeia
1963: 387-394.
Licht, Paul. 1968. Response of the thermal preferendum and heat resistance
to thermal acclimation under different photoperiods in the lizard Andis
carolinensis. Amer. Midi. Nat. 79: 149-158.
Licht, Paul and Allen G. Brown. 1967. Behavioral thermoregulation and
its role in the ecology of the red-bellied newt, Taricha rivularis.
Ecology 48: 598-611.
Lowe, Charles H., and Velma J. Vance. 1955. Acclimation of the critical
thermal maximum of the reptile Urosaurus ornatus. Science 122: 73-74.

83
Lucas, E. A. and W. A. Reynolds. 1967. Temperature selection by
amphibia larvae. Physiological Zoology 40: 159-171.
Lueth, F. X. 1941. Effects of temperature on snakes. Copeia 1941:
125-132.
Mackay, R. Stuart. 1964. Galapagos tortoise and marine iguana deep
body temperatures measured by radio telemetry. Nature 204: 355-458.
Mayhew, W. W. 1963. Temperature preferences of Sceloporus orcutti.
Herpetologica 18: 217-233.
McGinnis, S. M. 1967. Telemetry applied to studies of thermoregulation
in reptiles. Proc. 1967 Nat. Telemet. Conf.: 252-254.
McGinnis, Samuel M. and Robert G. Moore. 1969. Thermoregulation in the
boa constrictor, Boa constrictor. Herpetologica 25: 38-45.
Molnar, G. and I. Tolg. 1962. Relation between water temperature and
gastric digestion of largemouth bass, Micropterus salmoides Lacepede.
J. Fish. Res. Bd. Can. 19: 1005-1012.
Mueller, Charles F. 1969. Temperature and energy characteristics of the
sagebrush lizard (Seeloporus graciosus) in Yellowstone National Park.
Copeia 1969: 153-160.
Myres, Brian C. and Murray M. Eells. 1968. Thermal aggregation in Boa
constrictor. Herpetologica 24: 61-66.
Norris, Kenneth S. 1953. The ecology of the desert iguana, Dipsosaurus
dorsalis. Ecology 34: 265-287.
Norris, Kenneth S. 1963. The functions of temperature in the ecology of
the percoid fish Girella nigricans (Ayres). Ecological Monographs
33: 23-62.
Osgood, David. 1970. Thermoregulation in water snakes studied by telemetry.
Copeia 1970: 568-571.
Pegel, W. A. 1939. Motornaja finkeija pistchevaritelnoj sistemy ryb v
uslovijach razlitschnoj temperatury sredy. Trudy biol. Nauchno-issled.
Inst, tomsk. gos Univ. 6: 51-67.
Peters, James A. 1964. Dictionary of Herpetology. Hafner Publishing
Company, New York.
Pianka, Eric R. 1971. Comparative ecology of two lizards. Copeia 1971:
129-138.
Regal, P. J. 1966. Thermophilic responses following feeding in certain
reptiles. Copeia 1966: 588-590.
Regal, P. J. 1967. Voluntary hypothermia in reptiles. Science 155: 1551-1553.
Riddle, 0. 1909. The rate of digestion in cold-blooded vertebrates --
influence of season and temperature. Am. J. Physiol. 24: 447-458.
the

84
Root, H. D. 1961. Gastric digestion with hypothermia: observations
and applications. Thesis, University of Minnesota, 1-154.
Ruibal, Rodolfo. 1961. Thermal relations of five species of tropical
lizards. Evolution 15: 98-111.
Schmidt-Nielsen, Knut and William R. Dawson. 1964. Terrestrial animals
in drj, heat: desert reptiles. 467-480. In: D. B. Dill (ed.).
Handbook of Physiology. Sect. 4. "Adaptation to the Environment."
Amer. Physiol. Soc., Washington, D. C.
Skoczylas, Rafaí. 1970. Influence of temperature on gastric digestion in
the grass snake Natrix natrix L. Comp. Biochem. Physiol. 33: 793-804.
Soule, Michael. 1963. Aspects of thermoregulation in nine species of
lizards from Baja, California. Copeia 1963: 107-115.
Stewart, Glenn R. 1965. Thermal ecology of the garter snakes Thamnophis
sirtalis concinnus (Hallowell) and Thamnophis ordinoides (Baird and
Girard). Herpetologica 21: 81-102.
Wangensteen, 0. H., H. D. Root, C. B. Jenson*, K. Imamoglu, and P. A. Salmon.
1958. Depression of gastric secretion and digestion by gastric hypo¬
thermia. Its clinical use in massive hematomesis. Surgery 44: 265-274.
Weathers, Wesley W. 1970. Physiological thermoregulation in the lizard
Dipsosaurus dorsalis. Copeia 1970: 549-557.
Wilhoft, D. C. 1958. Observations on preferred body temperatures and
feeding habits of some selected tropical iguanas. Herpetologica
14: 161-164.
Wilhoft, D. C. and J. D. Anderson. 1960. Effect of acclimation on the
preferred body temperature of the lizard Sceloporus occidentalis.
Science 131: 610-611.

BIOGRAPHICAL SKETCH
Donald Eugene Goodman was born January 30, 1944, at Kennett,
Missouri. In June, 1966, he received the degree of Bachelor of
Arts with a major in Zoology from the University of Missouri. In
1966, he enrolled in the Graduate School of the University of Florida
and has until the pi'esent time pursued his work toward the degree of
Doctor of Philosophy in the Department of Zoology.
Donald Eugene Goodman is a member of the American Society of
Ichthyologists and Herpetologists and the American Association for
the Advancement for Science.
85

I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.
A. F. Carr, Jr., Chairman
Graduate Research Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.
â– Jkifikt
B. K. McNab, Co-Chairman
Associate Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.
G. Nordlie
Associate Professor of Zoology
I certify that I have read this study and that in my opinion it
conforms to acceptable standards of scholarly presentation and is fully
adequate, in scope and quality, as a dissertation for the degree of
Doctor of Philosophy.
E. S. Ford
Professor of Botany

This dissertation was submitted to the Dean of the College of Arts
and Sciences and to the Graduate Council, and was accepted as partial
fulfillment of the requirements for the degree of Doctor of Philosophy.
June, 1971
Dean, Graduate School

6
UNIVERSITY OF FLORIDA
I m ni inn in» -
3 1262 08556 7401




PAGE 1

7KHUPRUHJXODWLRQ LQ WKH %URZQ :DWHU 6QDNH 1DWUL[ WD[LVSLORWD ZLWK 'LVFXVVLRQ RI WKH (FRORJLFDO 6LJQLILFDQFH RI 7KHUPDO 3UHIHUHQFLD LQ WKH 2UGHU 6TXDPDWD %\ '21$/' (8*(1( *22'0$1 $ ',66(57$7,21 35(6(17(' 72 7+( *5$'8$7( &281&,/ 2) +,( 81,9(56,7< 2) )/25,'$ ,1 3$57,$/ )8/),//0(17 2) 7+( 5(48,5(0(176 )25 7+( '(*5(( 2) '2&725 2) 3+,/2623+< 81,9(56,7< 2) )/25,'$

PAGE 2

7KLV ZRUN LV GHGLFDWHG WR P\ SDUHQWV $UYLO ( *RRGPDQ DQG &ODUD 0HWFDOI *RRGPDQ ZKR HQFRXUDJHG P\ SXUVXLW RI ELRORJ\ LQ JHQHUDO DQG VQDNHV LQ SDUWLFXODU

PAGE 3

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

PAGE 4

7$%/( 2) &217(176 3DJH $&.12:/('*(0(176 LLL /,67 2) 7$%/(6 YL /,67 2) ),*85(6 YLL $%675$&7 f f f L[ ,1752'8&7,21 0$7(5,$/6 $1' 0(7+2'6 &ROOHFWLRQ DQG 0DLQWHQDQFH RI 6SHFLPHQV 5DGLR 7HOHPHWU\ ([SHULPHQWDO $SSDUDWXV 7KHUPDO *UDGLHQW 0HWDEROLVP 'LJHVWLYH (IILFLHQF\ 5(68/76 $1' ',6&866,21 3UHIHUUHG %RG\ 7HPSHUDWXUH %HKDYLRUDO 7KHUPRUHJXODWLRQ 0RUQLQJ (PHUJHQFH (IIHFW RI DLU DQG ZDWHU WHPSHUDWXUHV (IIHFW RI DFFOLPDWLRQ (IIHFW RI SK\VLRORJLFDO VWDWH (IIHFW RI OLJKW 7HPSRUDO FKDQJHV LQ HPHUJHQFH UHVSRQVH 0DLQWHQDQFH RI 3UHIHUUHG %RG\ 7HPSHUDWXUH (YHQLQJ 6XEPHUJHQFH LY

PAGE 5

)DFWRUV $IIHFWLQJ 3UHIHUUHG %RG\ 7HPSHUDWXUH 'LJHVWLRQ 2WKHU )DFWRUV (FRORJLFDO 6LJQLILFDQFH RI 5HSWLOLDQ 3%7 6800$5< /,67 2) 5()(5(1&(6 %,2*5$3+,&$/ 6.(7&+ Y

PAGE 6

/,67 2) 7$%/(6 7DEOH 3DJH 7KH SUHIHUUHG UDQJHV RI ERG\ WHPSHUDWXUH RI IUHVKO\ FDXJKW 1DWUL[ WD[LVSLORWD (IIHFW RI GLJHVWLRQ RQ QRUPDO UDQJH RI SUHIHUUHG ERG\ WHPSHUDWXUHV 'DWD IRU SRLQWV SORWWHG LQ )LJXUH IRU SULPDU\ KHOLRWKHUPLF OL]DUGV 'DWD IRU SRLQWV SORWWHG LQ )LJXUH IRU QRFWXUQDO UHSWLOHV 'DWD IRU SRLQWV SORWWHG LQ )LJXUH IRU GLXUQDO VQDNHV DQG IRUHVW OL]DUGV

PAGE 7

/,67 2) ),*85(6 )LJXUH 3DJH ;UD\ SKRWRJUDSK RI D 1DWUL[ WD[LVSLORWD ZLWK DQ LQJHVWLEOH UDGLR WUDQVPLWWHU LQ LWV VWRPDFK ([SHULPHQWDO SHQ DW /DNH $OLFH ([SHULPHQWDO FKDPEHU XVHG WR GHWHUPLQH WKH UHVSRQVHV RI ZDWHU VQDNHV WR YDULRXV FRPELQDWLRQV RI DLU DQG ZDWHU WHPSHUDWXUH (IIHFW RI DFFOLPDWLRQ WHPSHUDWXUH RQ WKH UDQJH RI ERG\ WHPSHUDWXUHV VHOHFWHG E\ 1DWUL[ WD[LVSLORWD LQ D JUDGLHQW A 1DWUL[ WD[LVSLORWD ERG\ WHPSHUDWXUHV DQG DVVRFLDWHG DLU WHPSHUDWXUHV DW 1HPDQnV /DNH GXULQJ 'HFHPEHU DQG -DQXDU\ 1DWUL[ WD[LVSLORWD ERG\ WHPSHUDWXUHV DQG DVVRFLDWHG DLU WHPSHUDWXUHV DW 1HZQDQnV /DNH GXULQJ 0DUFK %RG\ WHPSHUDWXUH RI 1DWUL[ WD[LVSLORWD FROOHFWHG DW 1HZQDQnV /DNH EHWZHHQ DQG KRXUV IURP 0DUFK WKURXJK 2FWREHU 0HWDEROLF UDWH RI 1DWUL[ WD[LVSLORWD DV D IXQFWLRQ RI DFFOLPDWLRQ WHPSHUDWXUH DQG ERG\ ZHLJKW %HKDYLRUDO UHVSRQVHV RI D J 1DWUL[ WD[LVSLORWD WR FRPELQDWLRQV RI DLU DQG ZDWHU WHPSHUDWXUH IURP r& WKURXJK r& %RG\ WHPSHUDWXUHV RI 1DWUL[ WD[LVSLORWD DQG DVVRFLDWHG DLU WHPSHUDWXUHV DW WLPH RI FDSWXUH DW 1HZQDQnV /DNH $YHUDJH ERG\DLU WHPSHUDWXUH GLIIHUHQWLDOV RI 1DWUL[ WD[LVSLORWD DW 1HZQDQnV /DNH DV D IXQFWLRQ RI DLU WHPSHUDWXUH 1XPEHU RI 1DWUL[ WD[LVSLORWD EDVNLQJ RQ YDULRXV GD\V WKURXJKRXW WKH \HDU 1XPEHU RI 1DWUL[ WD[LVSLORWD EDVNLQJ DW YDULRXV WLPHV RQ $SULO YLL

PAGE 8

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

PAGE 9

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n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r& ,W LV VXJJHVWHG WKDW KLJK WKHUPDO H[WUHPHV DUH VHOHFWLYH IRUFHV ZKLFK GLUHFWO\ IL[ WKH FULWLFDO WKHUPDO PD[LPXP RI UHSWLOHV DQG LQGLUHFWO\ IL[ WKH SUHIHUUHG ERG\ WHPSHUDWXUH 7KH UHODWLYHO\ ORZ WKHUPDO SUHIHUHQGD RI VQDNHV PD\ EH D IXQFWLRQ RI WKHLU ODFN RI OLPEV ZKLFK SUHFOXGHV WKHUPRn UHJXODWLRQ ZLWK WKH GHJUHH RI LQGHSHQGHQFH RI FRQGXFWLYH KHDW H[FKDQJH ZLWK WKH VXEVWUDWH FKDUDFWHULVWLF RI OL]DUGV

PAGE 10

,1752'8&7,21 0DQ\ VSHFLHV RI UHSWLOHV XWLOL]H VRODU UDGLDWLRQ WR DWWDLQ ERG\ WHPSHUDWXUHV JUHDWO\ LQ H[FHVV RI DPELHQW WHPSHUDWXUHV 6RPH VSHFLHV KDYH DQ H[WHQVLYH EHKDYLRUDO UHSHUWRLUH ZKLFK HQDEOHV WKHP WR UHJXODWH WKHLU ERG\ WHPSHUDWXUH ZLWKLQ IDLUO\ QDUURZ OLPLWV 6LQFH WKHVH LQLWLDO GLVFRYHULHV ZHUH UHSRUWHG &RZOHV DQG %RJHUW f VFRUHV RI SDSHUV KDYH DSSHDUHG GRFXPHQWLQJ VXFK EHKDYLRU IRU RWKHU UHSWLOLDQ VSHFLHV DQG LW QRZ VHHPV REYLRXV WKDW WKHUPRUHJXODWLRQ LV D JHQHUDO IHDWXUH RI UHSWLOLDQ EHKDYLRU :KLOH VRPH UHSWLOHV SRVVHVV SK\VLRORJLFDO PHFKDQLVPV WKDW FRQWULEXWH WR WKHUPDO KRPHRVWDVLV /XHWK &ROH &RZOHV 5XLEDO %DUWKRORPHZ DQG 7XFNHU +HDWK +XWFKLVRQ HM DO .RXU DQG +XWFKLVRQ :HDWKHUV f LW LV EHKDYLRUDO XWLOL]DWLRQ GLUHFWO\ RU LQGLUHFWO\ RI VRODU UDGLDWLRQ WKDW SHUPLWV WKH DWWDLQPHQW RI KLJK SUHIHUUHG WKHUPDO OHYHOV 7KH FRQWULEXWLRQ RI PHWDEROLF KHDW WR PDLQWHQDQFH RI WKHUPDO KRPHRVWDVLV LV QHJOLJLEOH /XHWK &ROH 0DFND\ 6FKPLGW1LHOVHQ DQG 'DZVRQ %UDWWVWURP f HYHQ LQ ODUJH UHSWLOHV :LWK IHZ H[FHSWLRQV WKHVH VWXGLHV KDYH GHDOW ZLWK OL]DUGV DQG YHU\ OLWWOH LQIRUPDWLRQ H[LVWV IRU RWKHU UHSWLOLDQ JURXSV 7KH IHZ VWXGLHV RI WKHUPRUHJXODWLRQ LQYROYLQJ VQDNHV &RZOHV DQG %RJHUW &DUSHQWHU )LWFK %UDWWVWURP 6WHZDUW 0\UHV DQG (HOOV .LWFKHOO 0F*LQQLV DQG 0RRUH 2VJRRG f LQGLFDWH WKDW VQDNHV GLIIHU IURP OL]DUGV LQ WKHLU WKHUPDO EHKDYLRU 7KH\ VHHP WR KDYH ORZHU WKHUPDO SUHIHUHQGD DQG WR UHJXODWH OHVV SUHFLVHO\ 6RPH ZRUNHUV &RZOHV DQG %RJHUW 6FKPLGW1LHOVHQ

PAGE 11

DQG 'DZVRQ f EHOLHYH WKHVH GLIIHUHQFHV DUH FRUUHODWHG ZLWK GLIIHUHQFHV LQ WKH HFRORJ\ RI WKH WZR JURXSV 0RVW VQDNHV IRU LQVWDQFH DUH QRFWXUQDO RU FUHSXVFXODU DQG PDQ\ DUH IRVVRULDO OL]DUGV DUH PRVWO\ GLXUQDOO\ DFWLYH DQG WHUUHVWULDO (YHQ DPRQJ QRFWXUQDO DQG IRVVRULDO UHSWLOHV KRZHYHU EDVNLQJ LQ WKH VXQ KDV EHHQ HLWKHU UHJXODUO\ RU RFFDVLRQDOO\ UHSRUWHG &RZOHV DQG %RJHUW %DLOH\ %UDWWVWURP f 7KH VLJQLn ILFDQFH RI GLXUQDO WKHUPRUHJXODWLRQ LQ VXFK IRUPV KDV QHYHU EHHQ H[SORUHG 7KLV VWXG\ ZDV XQGHUWDNHQ WR GHWHUPLQH WKH VLJQLILFDQFH RI WKHUPRn UHJXODWLRQ LQ D VSHFLHV RI VQDNH ZKLFK LV ERWK VHPLDTXDWLF DQG QRFWXUQDOO\ DFWLYH 1DWUL[ WD[LVSLORWD WKH EURZQ ZDWHU VQDNHVSHQGV QLJKWV LQ WKH ZDWHU RI ODUJH RSHQ ODNHV RU ULYHUV DQG VSULQJV 'XULQJ WKH GD\OLJKW KRXUV RI WKH ZDQQHU PRQWKV WKH VSHFLHV FRPPRQO\ OLHV RQ OLPEV RYHUKDQJLQJ WKH ZDWHU HLWKHU LQ WKH VXQ RU LQ WKH VKDGH ([FHSW IRU UHSURGXFWLYH EHKDYLRU LQ WKH HDUO\ VSULQJ OLWWOH DFWLYLW\ RFFXUV GXULQJ WKH GD\ 7KLV VQDNH DOPRVW QHYHU RFFXUV DZD\ IURP WKH ZDWHUnV HGJH DQG WKH DHULDO SKDVH RI LWV H[LVWHQFH LV OLPLWHG WR EDVNLQJ RQ YHJHWDWLRQ UDWKHU WKDQ VKRUH :KLOH O\LQJ DERYH WKH ZDWHU WKH VQDNH LV VXUURXQGHG E\ D WKHUPDO PHGLXP WKDW LV YLUWXDOO\ KRPRJHQHRXV DQG KHDW H[FKDQJH LV ODUJHO\ UDGLDWLYH &RQYHFWLYH KHDW H[FKDQJH WKHUH LV PLQLPDO EHFDXVH VQDNHV UHPDLQ LQ WKH ZDWHU RQ ZLQG\ GD\V +HDW H[FKDQJH GXULQJ WKH DTXDWLF VWDJH RI WKH DFWLYLW\ F\FOH KRZHYHULV DOPRVW FRPSOHWHO\ FRQGXFWLYH %HFDXVH WKH VSHFLHVn DFWLYLW\ LV SDUWLWLRQHG DOPRVW FRPSOHWHO\ EHWZHHQ WKHVH WZR SKDVHV QRFWXUQDO DTXDWLF DFWLYLW\ DQG GLXUQDO DUERUHDO EDVNLQJ LW VHHPV DQ LGHDO VQDNH IRU D VWXG\ RI WKH PHFKDQLVPV DQG VLJQLILFDQFH RI WKHUPRn UHJXODWLRQ

PAGE 12

0$7(5,$/6 $1' 0(7+2'6 &ROOHFWLRQ DQG 0DLQWHQDQFH RI 6SHFLPHQV $OPRVW DOO WKH VQDNHV XVHG IRU WKLV VWXG\ ZHUH FROOHFWHG DW 1HZQDQn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

PAGE 13

6QDNHV XVHG IRU WKHUPDO JUDGLHQW GLJHVWLYH HIILFLHQF\ DQG PHWDEROLF H[SHULPHQWV ZHUH DFFOLPDWHG SULRU WR XVH (DFK DQLPDO ZDV KRXVHG LQ D SODVWLF VWRUDJH FRQWDLQHU ZLWK KROHV LQ WKH UHPRYDEOH OLG 7KHVH FRQWDLQHUV ZHUH SODFHG LQ D -HZHWW HQYLURQPHQWDO FDELQHW D )RUPD PRGHO LQFXEDWRU RU D /DE /LQH FRQWUROOHG HQYLURQPHQWDO URRP ZKHUH WKH WHPSHUDWXUH ZDV PDLQn WDLQHG ZLWKLQ r& $OO VQDNHV UHFHLYHG KRXUV RI OLJKW GDLO\ KRXUV (67f DQG KDG ZDWHU FRQWLQXRXVO\ DYDLODEOH LQ GLVKHV ZKLFK ZHUH WRR VPDOO WR SHUPLW VXEPHUJHQFH RI VQDNHV ZHLJKLQJ PRUH WKDQ J 5DGLR 7HOHPHWU\ ,QJHVWLEOH EORFNLQJ RVFLOODWRU UDGLR WUDQVPLWWHUV ZHUH XVHG WR REWDLQ VQDNH ERG\ WHPSHUDWXUHV XQGHU H[SHULPHQWDO FRQGLWLRQV 7KH EURDGFDVW IUHTXHQF\ XVHG ZDV ORZ HQRXJK NFf WR SHUPLW WKH UHn FHSWLRQ RI ERWK DHULDO DQG XQGHUZDWHU VLJQDOV JHQHUDWHG ZLWKLQ P RI WKH UHFHLYHU DQ $0)0 SRUWDEOH UDGLR $QWHQQDO ORRSV ZHUH DOZD\V QHFHVVDU\ WX UHOD\ WKH VLJQDO WR WKH UHFHLYHU (DFK F\OLQGULFDO UDGLXV PP OHQJWK PPf WUDQVPLWWHU ZDV SRZHUHG E\ D UHSODFHDEOH YROW VLOYHU R[LGH KHDULQJ DLG EDWWHU\ DQG ZDV ZDWHUSURRIHG ZLWK D WKLQ FRDW RI PL[WXUH RI EHHVZD[ DQG SDUDIILQ 7KH WUDQVPLWWHU ZDV OXEULFDWHG IRUFHG LQWR WKH WKURDW RI WKH VQDNH DQG PDVVDJHG E\ KDQG WR WKH VWRPDFK )LJ f 7KH WUDQVPLWWHU ZDV UHJXUJLWDWHG LQ IRXU RU PRUH GD\V GHSHQGLQJ RQ WHPSHUDWXUH 7UDQVn PLWWHUV ZHUH FDOLEUDWHG LPPHGLDWHO\ EHIRUH DQG DIWHU XVH ([SHULPHQWDO $SSDUDWXV 7R VWXG\ WKH IOXFWXDWLRQV RI ERG\ WHPSHUDWXUHV ZLWK FKDQJLQJ HQYLURQPHQWDO WHPSHUDWXUHV DQ H[SHULPHQWDO SHQ ZDV EXLOW DW DQRWKHU QHDUE\ ORFDWLRQ /DNH $OLFH 7KLV KHFWDUH ODNH LV ORFDWHG RQ WKH 8QLYHUVLW\ RI )ORULGD FDPSXV 7KH SHQ FRQVLVWHG RI D FLUFXODU JDOYDQL]HG VWHHO FDWWOH ZDWHULQJ WURXJK P LQ GLDPHWHU DQG FP KLJK &RQFUHWH

PAGE 14

)LJXUH ;UD\ SKRWRJUDSK RI D 1DWUL[ WD[LVSLORWD ZLWK DQ LQJHVWLEOH UDGLR WUDQVPLWWHU LQ LWV VWRPDFK

PAGE 16

EORFNV ZHUH VWDFNHG LQ WKH FHQWHU RI WKH WURXJK WR D OHYHO RI DERXW FP DQG D ZRRGHQ FDEOH VSRRO FP LQ GLDPHWHU ZDV SODFHG RQ LWV VLGH DWRS WKH EORFNV $Q DQWHQQDO ORRS V\VWHP ZDV LQVWDOOHG VR WKDW UDGLR WUDQVn PLWWHU VLJQDOV FRXOG EH PRQLWRUHG DW D GLVWDQFH IURP WKH SHQ 7KLV FRQVLVWHG RI D P VHFWLRQ RI LQVXODWHG FRSSHU FDEOH ULQJLQJ WKH SHQ LQ WKUHH SHUSHQGLFXODU SODQHV 7ZR ORRSV WKHUHIRUH SDVVHG XQGHU DQG RYHU WKH VSRRO DQG WKHLU FRPSRQHQWV H[WHQGLQJ DERYH WKH ULP RI WKH SHQ ZHUH VXSSRUWHG E\ DUFKHG VHFWLRQV RI VFUHHQ PRXOGLQJ )LJ f WKH WKLUG ORRS ZDV VLWXDWHG DORQJ WKH LQVLGH SHULSKHU\ DW WKH ULP 7KH HQGV RI WKLV DQWHQQDO ORRS ZHUH FRQQHFWHG WR D P VHFWLRQ RI LQVXODWHG FRSSHU ZLUH ZKLFK ZDV FRQQHFWHG E\ LQVXODWHG WLS SOXJV WR WKH DQWHQQD RI D SRUWDEOH $07 UDGLR 6LJQDOV JHQHUDWHG DQ\ZKHUH LQVLGH WKH ORRS FRXOG WKXV EH PRQLWRUHG PDQ\ PHWHUV DZD\ $ LQFK PHVK KDUGZDUH FORWK UHWDLQLQJ IHQFH ZDV DWWDFKHG WR WKH WRS HGJH RI WKH WURXJK DQG GLUHFWHG LQZDUG WRZDUG WKH FHQWHU RI WKH SHQ WR SUHYHQW WKH HVFDSH RI VQDNHV 7KLV DSSDUDWXV ZDV IORDWHG LQWR WKH ODNH DQG ILOOHG ZLWK ZDWHU WR WKH OHYHO RI WKH ERWWRP RI WKH ZRRGHQ VSRRO 7KH IUHHIORDWLQJ SHQ ZDV WKHQ DQFKRUHG DQG WKH ZLUH FRQQHFWLQJ WKH DQWHQQDO ORRS WR WKH UDGLR ZDV VXQN WR WKH ERWWRP EHWZHHQ WKH SHQ DQG WKH VKRUH 6QDNHV XVHG LQ WKLV SKDVH RI UHVHDUFK ZHUH LQWURGXFHG LQWR WKH SHQ DQG DOORZHG VHYHUDO GD\V WR DGMXVW WR WKHLU HQYLURQPHQW 7KH\ ZHUH WKHQ IRUFHIHG DQ LQJHVWLEOH WUDQVPLWWHU 2Q VXQQ\ GD\V WKH VQDNH KDG ERWK VXQQ\ DQG VKDGHG EDVNLQJ VLWHV DYDLODEOH RQ WKH ZRRGHQ VSRRO RU LW FRXOG UHPDLQ XQGHUZDWHU LQ WKH FDYLWLHV RI WKH FRQFUHWH EORFNV $LU ZDWHU DQG EODFNEXOE WHPSHUDWXUHV ZHUH PRQLWRUHG ZLWK HLWKHU D <6, WHOHn WKHUPRPHWHU ORFDWHG RQ VKRUH RU ZLWK PHUFXU\ EXOE WKHUPRPHWHUV ,Q WULDO GHWHUPLQDWLRQV WKH ZDWHU WHPSHUDWXUH LQVLGH DQG RXWVLGH WKH SHQ QHYHU GLIIHUHG E\ PRUH WKDQ r& 7KH ZDWHU LQVLGH ZDV VRPHWLPHV

PAGE 17

)LJXUH ([SHULPHQWDO SHQ DW /DNH $OLFH

PAGE 19

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n WUROOHG E\ FLUFXODWLQJ ZDWHU EHWZHHQ WKH DTXDULXP DQG D )RUPD FRQVWDQW WHPSHUDWXUH ZDWHU EDWK $ ERWWRPOHVV ZRRGIUDPH LQFK PHVK FDJH FP ; FP ; FPf ZLWK VOLGLQJ JODVV SDQHOV LQ IURQW ZDV SODFHG DERYH WKH DTXDULXP DQG 6DPEXFXV OLPEV ZHUH ZLUHG LQWR SRVLWLRQV ERWK XQGHUZDWHU DQG DERYH ZDWHU WR SURYLGH WKH VQDNHV ZLWK QXPHURXV UHVWLQJ DQG EDVNLQJ VLWHV $ ZDWW LQIUDUHG KHDW ODPS ZDV SODFHG GLUHFWO\ DERYH WKH ULJKW VLGH RI WKH FDJH DERXW FP DERYH WKH KLJKHVW EDVNLQJ VLWH $ ZRRGHQ SDUWLWLRQ ZDV KXQJ IURP WKH WRS RI WKH FDJH WKLV GLG QRW UHVWULFW PRYHPHQW EXW UDWKHU VKDGHG WKH OHIW VLGH RI WKH FDJH IURP VXQOLJKW )LJ f &DJHG DQLPDOV FRXOG WKXV HLWKHU UHPDLQ VXEPHUJHG RU EDVN DHULDOO\ LQ WKH VXQ RU VKDGH 7KLV DTXDULXPFDJHZDWHU EDWK FRPELQDWLRQ ZDV SODFHG LQVLGH D /DE /LQH FRQWUROOHG HQYLURQPHQWDO URRP ZKLFK PDLQWDLQV WHPSHUDWXUHV EHWZHHQ DQG r& ZLWKLQ r& :DWHU DLU DQG EODFNEXOE WHPSHUDWXUHV ZHUH PRQLWRUHG ZLWK D <6, WHOHWKHUPRPHWHU SODFHG RXWVLGH WKH URRP 7KH SUREHV ZHUH SODFHG LQVLGH WKH DTXDULXP SHQ LQ WKH ZDWHU VKDGHG DLU DQG DSSUR[LPDWHO\ FP GLUHFWO\ EHORZ WKH VXQODPS UHVSHFWLYHO\ 7KH EODFNEXOE SUREH ZDV FRDWHG ZLWK IODW EODFN SDLQW ,QJHVWLEOH WUDQVPLWWHUV ZHUH XVHG WR PRQLWRU ERG\ WHPSHUDWXUHV $ WKUHHSODQH DQWHQQDO ORRS ZDV SODFHG LQ WKH DTXDULXP FDJH DQG OHDGV ZHUH H[WHQGHG RXWVLGH WKH URRP WR WKH DQWHQQD RI DQ $0)0 UDGLR $OO

PAGE 20

)LJXUH ([SHULPHQWDO FKDPEHU XVHG WR GHWHUPLQH WKH UHVSRQVHV RI ZDWHU VQDNHV WR YDULRXV FRPELQDWLRQV RI DLU DQG ZDWHU WHPSHUDWXUH

PAGE 22

REVHUYDWLRQV ZHUH PDGH WKURXJK WZR FP ; FP KROHV LQ D VKHHW RI EURZQ SDSHU ZKLFK FRYHUHG WKH JODVV GRRU RI WKH HQYLURQPHQWDO URRP :LWK WKLV DSSDUDWXV DLU DQG ZDWHU WHPSHUDWXUHV FRXOG EH PRQLWRUHG DQG YDULHG LQGHSHQGHQWO\ WKH VQDNHnV EHKDYLRUDO DGMXVWPHQWV FRXOG EH REVHUYHG DQG LWV ERG\ WHPSHUDWXUH UHFRUGHG ZLWKRXW GLVWXUELQJ WKH DQLPDO 5HVSRQVHV RI WKH DQLPDOV ZHUH UHFRUGHG IRU DOO FRPELQDWLRQV RI DLU DQG ZDWHU WHPSHUDWXUHV IURP r WKURXJK r& $ WLPHU ZDV DWWDFKHG WR WKH HQYLURQPHQWDO URRP DQG D KRXU OLJKW F\FOH KRXUV (67f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r& WKURXJK r& ZHUH UXQ (DFK FRPELQDWLRQ ZDV UXQ IRU WZR KRXUV DQG WKHQ WKH DLU WHPSHUDWXUH ZDV HOHYDWHG r& 6LQFH WKHVH WHPSHUDWXUH FKDQJHV ZHUH JUDGXDO WKHUH LV QR UHDVRQ WR EHOLHYH WKDW WKH VQDNHV XVHG LQ WKLV H[SHULPHQW ZHUH DFFOLPDWHG WR WHPSHUDWXUHV WR ZKLFK WKH\ ZRXOG QRW RUGLQDULO\ EH DFFOLPDWHG XQGHU WKH VDPH WKHUPDO FRQGLWLRQV LQ WKH ZLOG 7KHUPDO *UDGLHQW $ WKHUPDO JUDGLHQW ZDV XVHG WR GHWHUPLQH SUHIHUUHG ERG\ WHPSHUDWXUH OHYHOV LQ WKLV VSHFLHV 7KH JUDGLHQW FRQVLVWHG RI D UHFWDQJXODU RSHQ WRS ZRRGHQ ER[ PP ORQJ FP ZLGH DQG FP KLJK ZLWK D QLFNOHVWHHO

PAGE 23

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r& SHU FP EHWZHHQ r DQG r& FRXOG EH PDLQWDLQHG LQGHILQLWHO\ DIWHU DQ LQLWLDO HLJKW KRXU ZDUPXS SHULRG $FFOLPDWHG VQDNHV ZHUH IRUFHIHG LQJHVWLEOH WUDQVPLWWHUV DW DERXW KRXUV SODFHG LQ WKH JUDGLHQW DQG OHIW RYHUQLJKW IRU DGMXVWPHQW %RG\ WHPSHUDWXUH DQG ORFDWLRQ LQ WKH JUDGLHQW ZHUH UHFRUGHG DW DSSUR[LPDWHO\ KRXU LQWHUYDOV EHWZHHQ DQG KRXUV RI WKH IROORZLQJ GD\ 6QDNHV LQ WKH JUDGLHQW UHn FHLYHG WKH VDPH KRXU SKRWRSHULRG IURP RYHUKHDG OLJKWLQJ DV LQ WKHLU DFFOLPDWLRQ TXDUWHUV $ UHG OLJKW ZDV XVHG ZKHQ UHDGLQJV ZHUH WDNHQ GXULQJ KRXUV RI GDUNQHVV 0HWDEROLVP 0HWDEROLF UDWHV ZHUH PHDVXUHG ZLWK D %HFNPDQ R[\JHQ DQDO\]HU 0HWDEROLF FKDPEHUV FRQVLVWHG RI FP GLDPHWHU JODVV EDWWHU\ MDUV FP KLJK ZLWK KROHV GULOOHG DW ORZ DQG KLJK OHYHOV RQ WKH VLGHV WR OHW DLU LQ DQG RXW $ SOH[LJODVV OLG ZLWK D FP GLDPHWHU KROH IRU D VL]H UXEEHU VWRSSHU ZDV FHPHQWHG WR WKH WRS RI WKH FKDPEHU $FFOLPDWHG VQDNHV ZHUH LQWURGXFHG LQWR WKH FKDPEHU ZKLFK ZDV WKHQ VXEPHUJHG LQ D FRQWUROOHGWHPSHUDWXUH ZDWHUEDWK WKDW PDLQWDLQHG ZDWHU WHPSHUDWXUH ZLWKLQ r& $LU [UDV SXPSHG WKURXJK D FRLO RI FRSSHU WXELQJ WKDW ZDV VXEPHUJHG LQ WKH ZDWHU EDWK EHIRUH HQWHULQJ WKH FKDPEHU

PAGE 24

2[\JHQ FRQVXPSWLRQ UHDGLQJV ZHUH WDNHQ DW KDOIKRXU LQWHUYDOV XQWLO VWDEOH YDOXHV ZHUH REWDLQHG 'LJHVWLYH (IILFLHQF\ 7KH HIIHFW RI WHPSHUDWXUH XSRQ GLJHVWLYH HIILFLHQF\ ZDV PHDVXUHG FDORULPHWULFDOO\ $ OLUJH QXPEHU RI JL]]DUG VKDG 'RURVRPD FHSHGLDQXP ZHUH FROOHFWHG E\ URWHQRQH SRLVRQLQJ DW 1HPDQnV /DNH DQG LPPHGLDWHO\ IUR]HQ ,Q IHHGLQJ H[SHULPHQWV ILVK ZHUH ZHLJKHG JURXQG ZKROH LQ D :DULQJ EOHQGHU DQG IUHH]HGULHG LQ D 9LUWLV IUHH]HGU\LQJ DSSDUDWXV 7KH UHVXOWLQJ PL[WXUH ZDV JURXQG DJDLQ DQG ILOWHUHG WKURXJK LQFK PHVK VFUHHQLQJ WR UHPRYH VFDOHV DQG ODUJH VFDOH IUDJPHQWV 7KH UHn VXOWLQJ SRZGHU ZDV WKRURXJKO\ PL[HG DQG D WR J VDPSOH UHPRYHG IRU FDORULPHWULF GHWHUPLQDWLRQ LQ D 3DUU DGLDEDWLF R[\JHQ ERPE FDORULn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f WKH DFFXPXODWHG IHFHV ZHUH HLWKHU IUHH]HGULHG RU YDFXXP GHVVLFDWHG DQG WKH GU\ IHFHV ZHLJKHG DQG ERPEHG $W WKH WHPSHUDWXUHV RI r& DQG DERYH VQDNHV SDVVHG PXVN IURP WKH PXVN JODQGV WKH DPRXQW LQFUHDVLQJ ZLWK WHPSHUDWXUH 7KH TXDQWLW\ RI PXVN SHU J RI ERG\ ZHLJKW ZDV GHWHUPLQHG DW WKH DFFOLPDWLRQ WHPSHUDWXUHV XVHG DQG VDPSOHV ZHUH ERPEHG WR GHWHUPLQH FDORULPHWULF YDOXH $ FRUUHFWLRQ IRU WKLV IDFWRU ZDV LQWURGXFHG LQWR WKH FDOFXODWLRQV 'LJHVWLYH HIILFLHQF\ LV GHILQHG

PAGE 25

KHUH DV &I f 2Q ( r &L ZKHUH ( GLJHVWLYH HIILFLHQF\ &I FDORULF YDOXH RI IHFHV FDORULF YDOXH RI LQJHVWHG IRRG DQG FDORULF YDOXH RI PXVN 'ULHG VDPSOHV RI ILVK IHFHV DQG PXVN ZHUH ZHLJKHG WR WKH QHDUHVW JUDP RQ D 0HWWOHU + EDODQFH

PAGE 26

5(68/76 $1' ',6&866,21 3UHIHUUHG %RG\ 7HPSHUDWXUH 7KURXJKRXW WKLV GLVFXVVLRQ WKH WHUP SUHIHUUHG ERG\ WHPSHUDWXUH DEEUHYLDWHG 3%7f ZLOO EH XVHG LQ DFFRUGDQFH ZLWK 3HWHUV f ZKR GHILQHG LW DV WKDW WHPSHUDWXUH DW RU DERXW ZKLFK DOO PHPEHUV RI D UHSWLOLDQ VSHFLHV ZLOO PDLQWDLQ WKHPVHOYHV JLYHQ WKH RSSRUWXQLW\ WR VHOHFW SURSHU VXEVWUDWH H[SRVXUH WR VXQOLJKW RU RWKHU WKHUPDO IDFWRUV 7KH 3%7 FDQ WKXV UHIHU WR D WKHUPDO UDQJH DV LQLWLDOO\ GHILQHG &RZOHV DQG %RJHUW f RU WR WKH PHDQ RI WKDW UDQJH WKH ODWWHU EHLQJ PRUH XVHIXO IRU FRPSDULVRQV RI LQWHUVSHFLILF SUHIHUHQFHV 7KH OHYHO RI ERG\ WHPSHUDWXUH VHOHFWHG E\ 1DWUL[ WD[LVSLORWD LQ D WKHUPDO JUDGLHQW LV LQYHUVHO\ SURSRUWLRQDO WR WKH WHPSHUDWXUH DW ZKLFK WKH VQDNHV ZHUH DFFOLPDWHG )LJ f 7KLV LV FRQVLVWHQW ZLWK WKH ILQGn LQJV RI :LOKRIW DQG $QGHUVRQ f IRU 6FHORSRUXV RFFLGHQWDOLV 7KH HFRORJLFDO VLJQLILFDQFH RI VXFK LQWHUGHSHQGHQFH LV QRW LPPHGLDWHO\ FOHDU ,W PLJKW EH H[SHFWHG WKDW 3%7 ZRXOG EH LQGHSHQGHQW RI DFFOLPDWLRQ DV /LFKW f IRXQG LQ $QROLV DQG VHUYH DV DQ LPPXWDEOH IRFDO SRLQW IRU WKHUPRUHJXODWRU\ EHKDYLRU ,Q RWKHU YHUWHEUDWH SRLNLORWKHUPV VLPLODUO\ GLVSDUDWH UHVXOWV KDYH EHHQ REWDLQHG 5DQD SLSLHQV WDGSROHV /XFDV DQG 5H\QROGV f DQG PDQ\ ILVK 1RUULV )U\ f VKRZ FKDQJHV LQ 3%7 ZLWK DFFOLPDWLRQ EXW WKH SUHIHUUHG WKHUPDO OHYHO RI WKH QHZW 7DULFKD ULYXODULV FDQQRW EH VKLIWHG E\ DFFOLPDWLRQ /LFKW DQG %URZQ f 7KXV LW LV LPSRVVLEOH WR JHQHUDOL]H DERXW WKH FDSDFLW\ RI YHUWHEUDWH SRLNLORWKHUPV IRU DGMXVWPHQW RI WKHLU WKHUPDO SUHIHUHQGD

PAGE 27

)LJXUH (IIHFW RI DFFOLPDWLRQ WHPSHUDWXUH RQ WKH UDQJH RI ERG\ WHPSHUDWXUHV VHOHFWHG E\ 1DWUL[ WD[LVSLORWD LQ D JUDGLHQW

PAGE 29

(VSHFLDOO\ SX]]OLQJ LV WKH IDFW WKDW WKH UHODWLRQVKLS LQ 1DWUL[ WD[LVSLORWD LV LQYHUVH EHFDXVH WKH FULWLFDO WKHUPDO PD[LPXP LV GLUHFWO\ FRUUHODWHG ZLWK WKH DFFOLPDWLRQ WHPSHUDWXUH /RZH DQG 9DQFH /DUVRQ %UDGVKDZ .RXU DQG +XWFKLVRQ f DQG 3%7 DW OHDVW LQ LQWHUVSHFLILF FRPSDULVRQV LV GLUHFWO\ SURSRUWLRQDO WR FULWLFDO WKHUPDO PD[LPXP %UDWWVWURP VHH )LJ f 7KHVH LQFRQVLVWHQFLHV ZDUUDQW DQ H[DPLQDWLRQ RI WKH HFRORJLFDO VLJQLILFDQFH RI WKH SK\VLRORJLFDO FDSDFLW\ IRU WKHUPDO DFFOLPDWLRQ LQ WKHVH VQDNHV +LHUH LV VRPH HYLGHQFH WKDW VHDVRQDO DFFOLPDWLRQ RI 3%7 GRHV RFFXU LQ WHPSHUDWH ]RQH UHSWLOHV 0XHOOHU f IRXQG WKDW ERWK 3%7 PHDVXUHG LQ D JUDGLHQWf DQG FULWLFDO WKHUPDO PD[LPXP ZHUH KLJKHU LQ 6FHORSRUXV JUDFLRVXV FROOHFWHG LQ WKH VXPPHU WKDQ LQ WKRVH FROOHFWHG LQ WKH VSULQJ 6LPLODU LQFUHDVHV LQ WKH OHYHO RI ILHOG ERG\ WHPSHUDWXUHV IURP VSULQJ WR VXPPHU KDYH EHHQ IRXQG LQ WZR JDUWHU VQDNHV 7KDPQRSKLV VLUWDOLV DQG 7 EXWOHUL &DUSHQWHU f DQG LQ WZR OL]DUGV &QHPLGRSKRUXV VH[OLQHDWXV DQG 6FHORSRUXV ZRRGL %RJHUW f $ VLPLODU VHDVRQDO YDULDWLRQ ZDV IRXQG LQ ERG\ WHPSHUDWXUHV RI 1DWUL[ WD[LVSLORWD EXW WKH GLIIHUHQFHV ZHUH QRW FRQVLVWHQW ZLWK WKH ODERUDWRU\ HYLGHQFH IRU WKH UHODWLRQVKLS EHWZHHQ DFFOLPDWLRQ WHPSHUDWXUH DQG 3%7 7KH OHYHO RI ERG\ WHPSHUDWXUH LQ 'HFHPEHU DQG HDUO\ -DQXDU\ UDQJHG EHWZHHQ DQG r& DQG PRVW YDOXHV ZHUH EHORZ DLU WHPSHUDWXUHV )LJ f %\ ODWH -DQXDU\ KLJKHU DLU WHPSHUDWXUHV UHVXOWHG LQ ERG\ WHPSHUDWXUHV RI WR r& ZLWK YDOXHV DSSUR[LPDWLQJ DLU WHPSHUDWXUH ,Q 0DUFK PRVW ERG\ WHPSHUDWXUHV UDQJHG EHWZHHQ DQG r& )LJ f DQG H[FHHGHG DLU WHPSHUDWXUH 7KHVH REVHUYDWLRQV ZHUH PDGH RQ VXQQ\ DQG UHODWLYHO\ ZLQGOHVV GD\V ZKHQ EODFN EXOE WHPSHUDWXUHV H[FHHGHG DLU WHPSHUDWXUHV E\ WR r& 7KH RFFXUUHQFH RI VQDNH ERG\ WHPSHUDWXUHV EHORZ DLU WHPSHUDWXUH FDQ EH H[SODLQHG RQO\ DV UHVXOWLQJ IURP UHFHQW HPHUJHQFH IURP FRROHU ZDWHU DQG LQLWLDO HYDSRUDWLYH

PAGE 30

)LJXUH 1DWUL[ WD[LVSLORWD ERG\ WHPSHUDWXUHV DQG DVVRFLDWHG DLU WHPSHUDWXUHV DW 1HPDQnV /DNH GXULQJ $f ODWH 'HFHPEHU DQG HDUO\ -DQXDU\ DQG %f ODWH -DQXDU\

PAGE 31

$,5 7(03(5$785( r&f )LJXUH 0DWUL[ WD[LVSLORWD ERG\ WHPSHUDWXUHV DQG DVVRFLDWHG DLU WHPSHUDWXUHV DW 1HZQDQnV /DNH GXULQJ 0DUFK

PAGE 32

FRROLQJ 7KURXJKRXW WKH ZDUPHU PRQWKV ERG\ WHPSHUDWXUHV UHPDLQHG DSSUR[LPDWHO\ ZLWKLQ WKH UDQJH IRXQG LQ 0DUFK )LJ f EXW E\ PLG 2FWREHU ORZHU DLU WHPSHUDWXUHV DJDLQ FDXVHG D GHFUHDVH LQ WKH ILHOG ERG\ WHPSHUDWXUHV 7KXV ILHOG GDWD SURYLGHG QR HYLGHQFH RI WKH LQYHUVH UHODWLRQVKLS WKDW PLJKW EH H[SHFWHG EHWZHHQ VHDVRQDO WHPSHUDWXUH DQG SUHVXPDEO\ WKHUPDO DFFOLPDWLRQ RI 3%7f DQG OHYHO RI ERG\ WHPSHUDWXUH +RZHYHU WKHVH ILHOG YDOXHV IRU ZLQWHU UHSUHVHQW DW EHVW OHYHOV RI WHPSHUDWXUH DWWDLQDEOH DQG QRW QHFHVVDULO\ WKRVH SUHIHUUHG 6QDNHV FROOHFWHG LQ -DQXDU\ VHOHFWHG ZDUPHU WHPSHUDWXUHV LQ D JUDGLHQW WKDQ WKRVH FROOHFWHG LQ $SULO RU -XO\ 7DEOH f VXJJHVWLQJ WKDW DFFOLPDWLRQ RI 3%7 GRHV RFFXU LQ QDWXUH 7KH ERG\ WHPSHUDWXUHV VHOHFWHG E\ VQDNHV FROOHFWHG LQ $SULO DQG -XO\ GLG QRW GLIIHU VLJQLILFDQWO\ LQGLFDWLQJ WKDW WKHVH VQDNHV ZHUH DFFOLPDWHG WR D FRPPRQ WKHUPDO OHYHO WKHLU 3%7 'XULQJ WKH FROGHU ZHDWKHU RI -DQXDU\ KRZHYHU WKHUPRUHJXODWRU\ EHKDYLRU FHDVHG DQG WKH VQDNHV EHFDPH DFFOLPDWHG WR WKH FROGHU WKHUPDO UHJLPH RI WKH ZDWHU LQ ZKLFK WKH\ UHPDLQHG WRUSLG 7KHLU 3%7 DW WKLV WLPH UHn IOHFWHG WKLV DFFOLPDWLRQ 0HWDEROLF GDWD DOVR VXJJHVW WKLV UHODWLRQVKLS )LJXUH JLYHV WKH PHWDEROLF UDWH RI VQDNHV DV D IXQFWLRQ RI VL]H DQG DFFOLPDWLRQ WHPSHUDWXUH 7KH OHYHO RI PHWDEROLVP DW D JLYHQ WHPSHUDWXUH LV LQn YHUVHO\ FRUUHODWHG ZLWK DFFOLPDWLRQ WHPSHUDWXUH 7KLV UHODWLRQVKLS KDV EHHQ UHSRUWHG IRU ILVK DPSKLELDQV UHSWLOHV DQG PDQ\ LQYHUWHEUDWHV IRU H[WHQVLYH UHYLHZV VHH %HUJ %XOORFN )U\ f DQG DSSHDUV WR EH D QHDUO\ XQLYHUVDO FKDUDFWHULVWLF RI SRLNLORWKHUPV :KHQ VQDNHV ZHUH PDLQWDLQHG DW YDU\LQJ WKHUPDO UHJLPHV r& IURP KRXUV WKURXJK KRXUV r& IURP KRXUV WKURXJK KRXUVf KRZHYHU WKHLU PHWDEROLVP EHFDPH DFFOLPDWHG WR WKH KLJKHU RI WKH WZR WHPSHUDWXUHV )LJ f $FFOLPDWLRQ WR WKH KLJKHVW RI YDU\LQJ WHPSHUDWXUHV KDV EHHQ

PAGE 33

)LJXUH %RG\ WHPSHUDWXUHV RI 0DWUL[ WD[LVSLORWD FROOHFWHG DW 1HZQDQnV /DNH EHWZHHQ KRXUV IURP 0DUFK WKURXJK 2FWREHU

PAGE 34

180%(5 2) 5(&25'6 7(03(5$785( r&f

PAGE 35

7DEOH 7KH SUHIHUUHG UDQJHV RI ERG\ WHPSHUDWXUH RI IUHVKO\ FDXJKW 1DWUL[ WD[LVSLORWD -$18$5< $35,/ -8/< 3%7 5$1*( r&f 0($1 r 1 2%6f f f f f'LIIHUHQFHV EHWZHHQ PHDQV IRU $SULO DQG -XO\ DUH QRW VWDWLVWLFDOO\ VLJQLILFDQW EXW WKH PHDQ IRU -DQXDU\ GLIIHUV VLJQLILFDQWO\ S f IURP WKH RWKHU PHDQV

PAGE 36

UHSRUWHG IRU 5DQD SLSLHQV +XWFKLVRQ DQG )HUUDQFD f DQG IRU VHYHUDO VSHFLHV RI ILVK LQ ERWK WKH ILHOG %UHWW f DQG XQGHU FRQWUROOHG FRQGLWLRQV )U\ HW DO +HDWK f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r&f FRUUHODWHV DOPRVW H[DFWO\ ZLWK WKRVH SUHIHUUHG r&f E\ VQDNHV DFFOLPDWHG WR r& DQG r& D FORVH DJUHHPHQW EHWZHHQ ILHOG DQG ODERUDWRU\ GDWD 7KHUPRUHJXODFLRQ DW WKH SUHIHUUHG OHYHO DSSDUHQWO\ IL[HV WKH OHYHO RI WKHUPDO DFFOLPDWLRQ WKURXJKRXW WKRVH SDUWV RI WKH \HDUZKHQ DGHTXDWH WKHUPDO RSSRUWXQLWLHV H[LVW 'XULQJ WKH FROGHU PRQWKV ZKHQ WKLV LV QRW SRVVLEOH )LJ f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

PAGE 37

)LJXUH 0HWDEROLF UDWH RI 0DWUL[ WD[LVSLORWD DV D IXQFWLRQ RI DFFOLPDWLRQ WHPSHUDWXUH DQG ERG\ ZHLJKW $ DFFOLPDWHG WR r& % r& & r& r& ( YDU\LQJ WHPSHUDWXUHV r& QLJKW r& GD\f

PAGE 38

/2* 0(7$%2/L60 FF&AKUf /2* %2'< :(,*+7 Jf

PAGE 39

KLJKHVW DLU WHPSHUDWXUH UHFRUGHG LQ *DLQHVYLOOH LQ D \HDU SHULRG .LQFHU f LV r& ZKLFK LV VHYHUDO GHJUHHV EHORZ WKH SUREDEOH FULWLFDO WKHUPDO PD[LPXP IRU 1DWUL[ WD[LVSLORWD %UDWWVWURP f 2QO\ ZKHQ GUDVWLF FOLPDWLF ZDUPLQJ RFFXUV ZRXOG VQDNHV EHFRPH DFFOLPDWHG WR WHPSHUDWXUHV VLJQLILFDQWO\ DERYH WKHLU SUHIHUUHG UDQJH DQG WKHUH ZRXOG EH D FOHDU VHOHFWLYH SUHVVXUH IDYRULQJ LQGLYLGXDOV ZKR EHKDYLRU DOO\ VRXJKW FRRO ERG\ WHPSHUDWXUHV HYHQ LI WKH ORZHVW DWWDLQDEOH ERG\ WHPSHUDWXUH ZDV DERYH WKH SUHIHUUHG OHYHO %HKDYLRUDO 7KHUPRUHJXODWLRQ W 0RUQLQJ (PHUJHQFH r %URZQ ZDWHU VQDNHV DOPRVW LQYDULDEO\ VSHQG WKH QLJKW LQ WKH ZDWHU +LH WLPH RI HPHUJHQFH GHSHQGV XSRQ VHYHUDO FOLPDWLF IDFWRUV DQG XSRQ VRPH HQGRJHQRXV UHVSRQVHV RI WKH VQDNH 7KH HIIHFW RI DLU DQG ZDWHU WHPSHUDWXUHV RQ HPHUJHQFH )LJXUH VKRZV WKH UHVSRQVH RI D J IHPDOH ZDWHU VQDNH PDLQn WDLQHG LQ WKH HQYLURQPHQWDO FKDPEHU WR DOO FRPELQDWLRQV RI DLU DQG ZDWHU WHPSHUDWXUHV EHWZHHQ DQG r& 7KLV LQFOXGHV DOO WKH WKHUPDO UHJLPHV ZKLFK WKH VSHFLHV HYHU HQFRXQWHUV LQ QDWXUH DQG VHYHUDO DUWLILFLDO VLWXn DWLRQV 7KH UHVSRQVHV RI VHYHUDO RWKHU DQLPDOV WR D QXPEHU RI WKHVH WKHUPDO FRPELQDWLRQV QHYHU GLIIHUHG DSSUHFLDEO\ IURP WKRVH RI WKH J IHPDOH VR WKH SDWWHUQ VKRZQ LQ )LJXUH PD\ WKHUHIRUH EH FRQn VLGHUHG UHSUHVHQWDWLYH ,W VKRXOG EH UHPHPEHUHG WKURXJKRXW WKH GLVFXVVLRQ WKDW DQLPDOV XVHG LQ WKLV ODERUDWRU\ H[SHULPHQW ZHUH DGDSWHG WR WKH DSSUR[LPDWH WKHUPDO FRPELQDWLRQV WR ZKLFK WKHLU UHVSRQVHV ZHUH UHFRUGHG VHH 0DWHULDOV DQG 0HWKRGVf 7KH ORZHVW DLU WHPSHUDWXUH WKDW HOLFLWHG HPHUJHQFH ZDV r& DQG WKHQ RQO\ LI WKH ZDWHU WHPSHUDWXUH ZDV r& RU DERYH 7KLV ODWWHU FRPELQDWLRQ LV DQ DUWLILFLDO VLWXDWLRQ DW RQH H[WUHPH RI D JHQHUDO

PAGE 40

)LJXUH %HKDYLRUDO UHVSRQVHV RI D J 1DWUL[ WD[LVSLORWD WR FRPELQDWLRQV RI DLU DQG ZDWHU WHPSHUDWXUH IURP r& WKURXJK r& VQDNH VQDNH Â’ mmNH LQ ZDWHU LQ VXQ LQ VKDGH

PAGE 41

SDWWHUQ WKH FROGHU WKH ZDWHU WHPSHUDWXUH WKH ZDUPHU WKH DLU WHPSHUDWXUH QHHGHG WR HOLFLW HPHUJHQFH 7KH ORZHVW ZDWHU WHPSHUDWXUH DW ZKLFK VQDNHV HPHUJHG ZDV r& DQG WKHQ RQO\ LI DLU WHPSHUDWXUH ZDV DW OHDVW r& DJDLQ DQ DUWLILFLDO VLWXDWLRQf 7KHUH DUH WKHUHIRUH ORZHU OLPLWV IRU DLU DQG ZDWHU WHPSHUDWXUHV WKDW HOLFLW HPHUJHQFH LQ 1DWUL[ WD[LVSLORWD DQG DERYH WKHVH H[WUHPHV WKHVH PLQLPDO YDOXHV DUH LQYHUVHO\ UHODWHG 7KLV LQYHUVH UHODWLRQn VKLS LV QRW LVRWKHUPDO LH WKH VORSH RI WKLV DLUZDWHU WHPSHUDWXUH LQWHUIDFH LV QRW $W D ZDWHU WHPSHUDWXUH RI r& VQDNHV ZLOO HPHUJH IRU D PLQLPDO DLU WHPSHUDWXUH RI r& EXW DW ZDWHU WHPSHUDWXUHV EHORZ WKLV OHYHO DLU WHPSHUDWXUHV PXVW H[FHHG ZDWHU WHPSHUDWXUH WR HYRNH HPHUJHQFH )LJ f 7KH ORZHU WKH ZDWHU WHPSHUDWXUH WKH JUHDWHU WKH DLUZDWHU WHPSHUDWXUH GLIIHUHQWLDO UHTXLUHG IRU HPHUJHQFH 9DOXHV IRU WKLV GLIIHUHQWLDO DW RU QHDU WKH ZDWHU WHPSHUDWXUH DV\PSWRWH RI r& DUH DV PHQWLRQHG QRW HFRORJLFDOO\ VLJQLILFDQW EHFDXVH VXFK GLIIHUHQWLDOV GR QRW RFFXU LQ QDWXUH $W ZDWHU WHPSHUDWXUHV DERYH WKH DLUZDWHU LVRWKHUPDO HPHUJHQFH SRLQW r&f WKH PLQLPDO ZDWHU WHPSHUDWXUHV WKDW HYRNHG HPHUJHQFH ZHUH LQ H[FHVV RI DLU WHPSHUDWXUH 7KH KLJKHU WKH ZDWHU WHPSHUDWXUH IURP ZKLFK D VQDNH HPHUJHV WKH KLJKHU LWV ERG\ WHPSHUDWXUH DW HPHUJHQFH DQG WKH OHVV WLPH LW WDNHV D EDVNLQJ LQGLYLGXDO WR UHDFK WKH SUHIHUUHG WKHUPDO OHYHO 7KLV PD\ H[SODLQ ZK\ VQDNHV HPHUJH IURP ZDUP ZDWHU LQWR FRROHU DLU DW ZDWHU WHPSHUDWXUH DERYH r& $OWKRXJK WKH ZDWHU LV UHODWLYHO\ ZDUP LW LV VWLOO EHORZ WKH SUHIHUUHG OHYHO %DVNLQJ SHUPLWV DWWDLQPHQW RI 3%7 RU DW OHDVW D FORVHU DSSUR[LPDWLRQ WKDQ LV UHSUHVHQWHG E\ WKH ZDWHU WHPSHUDWXUH 7KXV VQDNHV DSSDUHQWO\ ZLOO QRW HPHUJH ZKHQ WKHLU ERG\ WHPSHUDWXUHV DUH

PAGE 42

EHORZ r& XQOHVV WKH DHULDO SKDVH LQVXUHV UDSLG DWWDLQPHQW RI WKLV OHYHO )LJXUH VXPPDUL]HV WKH ILHOG UHODWLRQVKLS EHWZHHQ DLU DQG ERG\ WHPSHUDWXUH ,W LV VLJQLILFDQW WKDW RQO\ SHUFHQW RI WKH ERG\ WHPSHUDWXUH UHFRUGV DUH EHORZ r& D FORVH DJUHHPHQW ZLWK ODERUDWRU\ UHVXOWV 7KH GHFUHDVH LQ QXPEHU RI UHFRUGV IRU VQDNH ERG\ WHPSHUDWXUH DW DLU WHPSHUDWXUHV EHORZ r& LV SUHFLSLWRXV DQG QRW D JUDGXDO DWWHQXn DWLRQ 7KH ERG\DLU GLIIHUHQWLDOV PDLQWDLQHG E\ VQDNHV DW DLU WHPSHUDWXUHV IURP r& WKURXJK r& DUH LQYHUVHO\ FRUUHODWHG ZLWK DLU WHPSHUDWXUH )LJ f 7KLV LV FOHDUO\ D UHIOHFWLRQ RI GLIIHUHQWLDO XWLOL]DWLRQ RI VXQOLJKW DV D IXQFWLRQ RI HQYLURQPHQWDO WHPSHUDWXUHV ,W LV HFRORJLFDOO\ VLJQLILFDQW WKDW WKHUH H[LVWV D ORZHU WKHUPDO WKUHVKROG IRU WKHUPRSKLOLF UHVSRQVHV DV HYLGHQFHG E\ WKH UHIXVDO RI VQDNHV WR HPHUJH DW ZDWHU DQG WKHUHIRUH ERG\f WHPSHUDWXUHV EHORZ r& HYHQ ZKHQ DLU WHPSHUDWXUH ZDV ZDUPHU %HORZ WKH ERG\ WHPSHUDWXUH UHTXLUHG IRU FRRUGLQDWHG ORFRPRWLRQ HPHUJHQW VQDNHV ZRXOG EH YHU\ YXOQHUDEOH WR SUHGDWLRQ E\ KRPRLRWKHUPV $OVR DW WHPSHUDWXUHV EHORZ WKH WKUHVKKROGV IRU IHHGLQJ DQG GLJHVWLRQ WKHUPRSKLOLF UHVSRQVHV ZRXOG LQFUHDVH WKH PHWDEROLF PDLQWHQDQFH FRVW ZLWKRXW SURYLGLQJ DGGLWLRQDO HQHUJ\ VRXUFHV 7KLV ZRXOG GHSOHWH WKH UHSWLOHnV HQHUJ\ VWRUHV QHHGHG IRU SHULRGV RI WRUSRU DQG DW KLJKHU ODWLWXGHVf KLEHUn QDWLRQ :KHQ WKH ZDWHU WHPSHUDWXUH DSSURDFKHG WKH ORZHU OLPLW RI WKH SUHIHUUHG UDQJH r&f D FRPPRQ RFFXUUHQFH EHWZHHQ $SULO DQG 2FWREHU WKH PLQLPDO DLU WHPSHUDWXUH UHTXLUHG WR HYRNH HPHUJHQFH LQFUHDVHG VKDUSO\ IURP r& DW r& ZDWHU WHPSHUDWXUH WR r& DW r& ZDWHU WHPSHUDWXUH )LJ f $W ZDWHU WHPSHUDWXUHV DERYH r& WKH PLQLPDO DLU WHPSHUDWXUHV QHFHVVDU\ IRU HPHUJHQFH ZHUH LQYHUVHO\ SURSRUWLRQDO

PAGE 43

)LJXUH %RG\ WHPSHUDWXUHV RI 1DWUL[ WD[LVSLORWD DQG DVVRFLDWHG DLU WHPSHUDWXUHV DW WLPH RI FDSWXUH DW 1HYDUDQnV /DNH

PAGE 44

OE E OL  $,5 7(03(5$785( r&f

PAGE 45

)LJXUH $YHUDJH ERG\DLU WHPSHUDWXUH GLIIHUHQWLDOV RI 1DWUL[ WD[LVSLORWD DW 1HZQDQnV /DNH DV D IXQFWLRQ RI DLU WHPSHUDWXUH 'DWD DUH WKH VDPH DV WKRVH SORWWHG LQ )LJXUH 1XPEHUV LQ SDUHQWKHVHV LQGLFDWH QXPEHU RI VQDNHV LQ HDFK FDWHJRU\

PAGE 46

/ F F] /8 4B XM M &I F 8( £ 4 2 & $,5 7(03(5$785( r&f

PAGE 47

WR ZDWHU WHPSHUDWXUHV 7KLV VKDUS LQFUHDVH LQ WKH PLQLPDO DLU WHPSHUn DWXUHV QHFHVVDU\ WR HOLFLW HPHUJHQFH VXJJHVWV WKDW ZDWHU LV RI FRQn VLGHUDEOH LPSRUWDQFH IRU WKHUPRUHJXODWLRQ EHWZHHQ $SULO DQG 2FWREHU ZKHQ VXFK WKHUPDO FRQGLWLRQV DUH FRPPRQ :KHQ ZDWHU WHPSHUDWXUHV H[FHHGHG WKH 3%7 HPHUJHQFH LQWR ORZHU DLU WHPSHUDWXUHV SHUPLWWHG FRROLQJ WR WKH SUHIHUUHG OHYHO 7KHVH ZDWHUDLU WHPSHUDWXUH GLIIHUHQn WLDOV SUREDEO\ QHYHU REWDLQ LQ QDWXUH DQG RUGLQDULO\ ZDWHU WHPSHUDn WXUHV DSSUHFLDEO\ DERYH DLU WHPSHUDWXUH ZRXOG RFFXU LQ WKH HYHQLQJ ZHOO DIWHU WKH HPHUJHQFH SHULRG 7KH HIIHFW RI DFFOLPDWLRQ RQ HPHUJHQFH $QLPDOV XVHG LQ WKH HQYLURQPHQWDO URRP VWXGLHV ZHUH DGDSWHG WR WKH DLUZDWHU WHPSHUDWXUH FRPELQDWLRQV WR ZKLFK WKHLU UHVSRQVHV DUH JUDSKHG LQ )LJ ,Q WKH ZLOG WKLV LV QRW DOZD\V WKH FDVH 6XGGHQ FOLPDWLF FKDQJHV PD\ UHVXOW LQ H[SRVXUH RI VQDNHV WR D WKHUPDO HQYLURQn PHQW WR ZKLFK WKH\ DUH QRW SK\VLRORJLFDOO\ DGDSWHG )RU LQVWDQFH WKH VDPH DSSUR[LPDWH DLU DQG ZDWHU WHPSHUDWXUH UDQJHV RQ )HEUXDU\ DQG $SULO UHVXOWHG LQ WKH HPHUJHQFH RI DQG VQDNHV UHVSHFWLYHO\ )LJ f %RWK GD\V ZHUH UHODWLYHO\ KXPLG DQG ZLQGOHVV VR WKH GLVSDULW\ VHHPV WR EH D UHIOHFWLRQ RI WKH GLIIHUHQFH LQ FOLPDWLF FRQGLWLRQV GXULQJ WKH ZHHN SUHFHHGLQJ WKHVH GDWHV $SULO ZDV ZDUP DQG W\SLFDO RI WKH ZHDWKHU RI WKLV SHULRG DQG VQDNHV ZHUH SK\VLRn ORJLFDOO\ DFFOLPDWHG WR WKHLU 3%7 )HEUXDU\ KRZHYHU ZDV WKH ZDUPHVW GD\ RI D IRXU GD\ ZDUPLQJ WUHQG 1LJKW DLU WHPSHUDWXUHV KDG EHHQ DW RU QHDU IUHH]LQJ XQWLO )HEUXDU\ 7KHVH VQDNHV WKHQ ZHUH DFFOLPDWHG WR WHPSHUDWXUHV ZHOO EHORZ WKRVH RI )HEUXDU\ DQG WKH EDVNLQJ UHVSRQVH ZDV JUHDWO\ DFFHQWXDWHG 7KHVH GDWD DQG WKH UHn ODWLRQVKLS EHWZHHQ DFFOLPDWLRQ WHPSHUDWXUH DQG 3%7 VXJJHVW WKDW WKH PLQLPDO DLU DQG ZDWHU WHPSHUDWXUH FRPELQDWLRQV UHTXLUHG WR HOLFLW HPHUJHQFH DQG EDVNLQJ DUH ORZHU LQ FROG WKDQ LQ ZDUPDFFOLPDWHG VQDNHV

PAGE 48

)LJXUH 1XPEHU RI 1DWUL[ WD[LVSLORWD EDUVf EDVNLQJ DW 1HZQDQnV /DNH RQ YDULRXV GD\V WKURXJKRXW WKH \HDU VXPPDWLRQ RI GDWD IURP DQG f DQG WKH UDQJHV RI DLU WHPSHUDWXUH YHUWLFDO OLQHVf UHFRUGHG DW WKH *DLQHVYLOOH ZHDWKHU VWDWLRQ IRU WKRVH GD\V

PAGE 49

180%(5 2) 61$.( $,5 7(03(5$785( 5$1*( F&f

PAGE 50

(IIHFW RI SK\VLRORJLFDO VWDWH XSRQ HPHUJHQFH $W RQ $SULO D VQDNH ZDV IRXQG EDVNLQJ ZLWK D ERG\ R WHPSHUDWXUH RI & &RUUHVSRQGLQJ DLU DQG ZDWHU WHPSHUDWXUHV DW WKH WLPH ZHUH r& DQG r& UHVSHFWLYHO\ 7KHVH ZHUH WKH ORZHVW ERG\ WHPSHUDWXUH DQG DVVRFLDWHG HQYLURQPHQWDO WHPSHUDWXUHV UHFRUGHG GXULQJ WKLV VWXG\ )LJ f ,W LV SUREDEO\ VLJQLILFDQW WKDW WKLV LQGLYLGXDO KDG D SURPLQHQW EXOJH IURP D ILVK LW KDG UHFHQWO\ HDWHQ ,W LV SRVVLEOH WKDW WKH PLQLPXP DLU DQG ZDWHU WHPSHUDWXUHV QHFHVVDU\ WR HYRNH EDVNLQJ PD\ EH ORZHU LQ VQDNHV GLJHVWLQJ IRRG WKDQ LQ WKRVH LQ D SRVWDEVRUSWLYH VWDWH 3UHVXPDEO\ KLJKHU ERG\ WHPSHUDWXUHV VKRXOG IDFLOLWDWH GLJHVWLYH SURFHVVHV LQ UHSWLOHV &RZOHV DQG %RJHUW 5HJDO f (IIHFW RI OLJKW RQ HPHUJHQFH &RPELQDWLRQV RI DLU DQG ZDWHU WHPSHUDWXUHV LGHDO IRU EDVNLQJ GLG QRW LQGXFH HPHUJHQFH DW DQ\ KRXU LQ WKH DEVHQFH RI OLJKW :KHQ WKH VXQ ODPS ZDV WXUQHG RQ GXULQJ WKH QLJKW VQDNHV EDVNHG LI WKHUPDO FRQGLWLRQV ZHUH SURSHU %R\HU f IRXQG WKDW WXUWOHV DOVR ZRXOG EDVN LQ UHVSRQVH WR OLJKW DW DQ\ WLPH 'XULQJ FORXG\ ZHDWKHU EDVNLQJ EHKDYLRU ZDV HLWKHU GLPLQLVKHG LH IHZHU LQGLYLGXDOV HPHUJHGf RU HPHUJHQFH ZDV GHOD\HG %R\HU f IRXQG WKLV DOVR WR EH WUXH IRU WXUWOHV ,Q WKH VHPLDTXDWLF UHSWLOHV VWXGLHG WKHUHIRUH EDVNLQJ EHKDYLRU GRHV QRW DSSHDU WR EH DQ HQGRJHQRXV UK\WKP EXW D UHVSRQVH WR WKH SURSHU FRQGLWLRQV RI OLJKW ZDWHU WHPSHUDWXUH DQG DLU WHPSHUDWXUH 7KH SK\VLRORJLFDO VWDWH RI WKH DQLPDO LV DQ LPSRUWDQW IDFWRU LQ GHWHUPLQLQJ WKH OHYHO RI WKH HQYLURQPHQWDO WHPSHUDWXUHV QHFHVVDU\ WR LQGXFH HPHUJHQFH )LJXUH SUHVHQWV WKH WKHUPDO HQYLURQPHQW DW 1HZQDQnV /DNH RQ $SULO DQG WKH HPHUJHQFH UHVSRQVH RI VQDNHV &OLPDWLF FRQGLWLRQV

PAGE 51

)LJXUH 7KH QXPEHU RI 1DWUL[ WD[LVSLORWD EDVNLQJ DW 1HZQDQnV /DNH DW YDULRXV WLPHV RQ $SULO DQG WKH DVVRFLDWHG DLU ZDWHU DQG EODFN EXOE WHPSHUDWXUHV

PAGE 52

180%(5 2) 61$.(6 7(03(5$785( r&f

PAGE 53

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r& DQG UHVSRQVHV ZHUH UHFRUGHG 8QGHU VXFK FRQGLWLRQV WKHUH RFFXUUHG D WHPSRUDO FKDQJH LQ WKH VQDNHVn SURSHQVLW\ IRU HPHUJQFH 7HPSHUDWXUH FRPELQDWLRQV ZKLFK ZRXOG HOLFLW HPHUJHQFH EHIRUH DERXW KRXUV (67f FRXOG QRW HOLFLW LQLWLDO HPHUJHQFH DIWHU WKDW WLPH 7KH UHVSRQVHV UHFRUGHG LQ )LJ ZHUH DOO UHFRUGHG SULRU WR KRXUV 7KH KHDWLQJ UDWH D 7 r&KUf DQG JHQHUDO ZDUPLQJ SDWWHUQ DSSUR[LPDWH FRQGLWLRQV RFFXUULQJ LQ WKH ZLOG GXULQJ ZLQWHU 8QGHU ODERUDWRU\ FRQGLWLRQV KRXUV RFFXUUHG KDOIZD\ WKURXJK WKH VXQOLJKW F\FOH KRXUVf ,Q QDWXUH VL[ KRXUV DIWHU VXQULVH ZRXOG EH DERXW KRXUV (67 GXULQJ 'HFHPEHU DQG -DQXDU\ $Q DQLPDO LQLWLDOO\ HPHUJLQJ DIWHU WKLV WLPH LQ UHVSRQVH WR WKUHVKROG HPHUJHQFH WHPSHUDWXUHV ZRXOG EHJLQ WR WKHUPRUHJXODWH DW RU IROORZLQJ WKH SHDN DLU WHPSHUDWXUH RI WKH GD\ DQG ZRXOG FRQIURQW GHFUHDVLQJ DQG WKHUHIRUH VXEWKUHVKROGf DLU WHPSHUDWXUHV IRU WKH UHPDLQGHU RI WKH GD\ &OHDUO\ WKHQ WKLV WHPSRUDO UHVWUDLQW RQ WKH WKHUPRSKLOLF HPHUJHQFH UHVSRQVH LV QHFHVVDU\ WR UHVWULFW WKHUPRUHJXODWRU\ DFWLYLW\ WR WKHUPDOO\ KRVSLWDEOH SHULRGV 2WKHUZLVH H[WHQVLYH EDVNLQJ ZRXOG RFFXU DW ORZ ERG\ WHPSHUDWXUHV UHn VXOWLQJ LQ H[SRVXUH RI VQDNHV WR SUHGDWLRQ DW VXERSWLPDO DFWLYLW\ WHPSHUDWXUHV

PAGE 54

0DLQWHQDQFH RI 3UHIHUUHG %RG\ 7HPSHUDWXUH (ODERUDWH EHKDYLRUDO DGMXVWPHQWV SHUPLW VRPH OL]DUGV WR WKHUPR UHJXODWH ZLWKLQ YHU\ QDUURZ OLPLWV 'HVHUW OL]DUGV DSSDUHQWO\ KDYH WKH PRVW HODERUDWH EHKDYLRUDO UHSHUWRLUH LQFOXGLQJ SRVWXUDO DGMXVWn PHQWV %RJHUW 1RUULV +HDWK f UHWUHDW WR EXUURZV &RZOHV DQG %RJHUW 1RUULV 'H:LWW D E 0F*LQQLV f SDQWLQJ &ROH &RZOHV DQG %RJHUW 5XLEDO .RXU DQG +XWFKLVRQ f FOLPELQJ 1RUULV 'H:LWW Df DQG EXUURZLQJ &RZOHV DQG %RJHUW +HDWK f 3K\VLRORJLFDO PRGLILFDWLRQV DUH NQRZQ LQ WKHVH UHSWLOHV EXW DUH FOHDUO\ RI VHFRQGDU\ LPSRUWDQFH LQ WKHUPDO KRPHRVWDVLV 7KHUPRUHJXODWLRQ LQ VQDNHV KDV EHHQ VWXGLHG YHU\ OLWWOH DQG DYDLODEOH LQIRUPDWLRQ VXJJHVWV WKDW WKHUPDO FRQWURO LV QRW DV SUHFLVH DQG WKH EHKDYLRUDO UHSHUWRLUH QRW DV FRPSOH[ DV LQ WKH FDVH RI KHOLRWKHUPLF OL]DUGV )ROORZLQJ HPHUJHQFH EURZQ ZDWHU VQDNHV EDVNHG XQGHU WKH VXQODPS RU OD\ LQ WKH VKDGH DW KLJKHU DLU WHPSHUDWXUHVf XQWLO D ERG\ WHPSHUDWXUH LQ WKH SUHIHUUHG UDQJH ZDV UHDFKHG DQG WKHUHDIWHU PRYHG IURP WKH VXQ WR VKDGH WR ZDWHU LQ RUGHU WR PDLQWDLQ WKLV OHYHO 1R FRQVLVWHQW SRVWXUDO RU FRLOLQJ DGMXVWPHQWV ZHUH QRWHG 5HWUHDW WR WKH VKDGH RU HQWUDQFH LQWR VXQOLJKW XVXDOO\ UHTXLUHG WR PLQXWHV 7KLV VORZ SDFH LV SUREDEO\ WKH UHVXOW RI D VORZ KHDWLQJ DQG FRROLQJ UDWH WR EH H[SHFWHG LQ DQ DQLPDO RI VXFK EXON DQG WKH ZLGH UDQJH RI SUHn IHUUHG WHPSHUDWXUHV $W ZDWHU WHPSHUDWXUHV EHORZ r& DQG DSSURSULDWH DLU WHPSHUDWXUHVf VQDNHV HPHUJHG DQG EDVNHG LQ WKH VXQOLJKW XQWLO WKHLU 3%7 ZDV UHDFKHG DQG WKHQ PRYHG LQWR WKH VKDGH 7KHUH LV D EURDG ]RQH RI RYHUODS EHn WZHHQ DLU WHPSHUDWXUH DW ZKLFK DQLPDOV EDVNHG LQ WKH VXQ DQG WKRVH DW ZKLFK WKH\ UHWUHDWHG WR WKH VKDGH 7KLV DSSHDUV WR EH ODUJHO\ D

PAGE 55

UHIOHFWLRQ RI WKH GLVWDQFH EHWZHHQ WKH VQDNH DQG WKH VXQODPS WKH HFRORJLF HTXLYDOHQW ZRXOG EH WKH GLUHFWQHVV DQGRU LQWHQVLW\ RI VXQOLJKW 6LPLODUO\ WKHUH ZDV RYHUODS EHWZHHQ WKH DLU WHPSHUDWXUHV DW ZKLFK DQLPDOV OD\ LQ WKH VKDGH DQG WKRVH DW ZKLFK WKH\ HQWHUHG WKH ZDWHU 7KLV SUREDEO\ LV D UHIOHFWLRQ RI YDULDWLRQ LQ ERG\ WHPSHUDWXUH RI WKH VQDNH IURP RQH H[SHULPHQWDO UXQ WR WKH QH[W DW WKH WLPH LW UHWUHDWHG IURP WKH VXQOLJKW 7KH ORZHVW DLU WHPSHUDWXUH DW ZKLFK VQDNHV UHWUHDWHG WR VKDGH ‘ZDV LQYHUVHO\ SURSRUWLRQDO WR ZDWHU WHPSHUDWXUH DW ZDWHU WHPSHUDWXUHV IURP r& WKURXJK r& (YLGHQWO\ PRUH WLPH ZDV UHTXLUHG DW WKHVH ORZ ZDWHU WHPSHUDWXUHV HPHUJHQFH ERG\ WHPSHUDWXUHVf IRU DWWDLQPHQW RI SUHIHUUHG OHYHOV 7KLV UHVXOWHG LQ WKH UHFRUGHG H[WUHPH RI D VQDNH EDVNLQJ LQ WKH VXQ DW DQ DLU WHPSHUDWXUH RI r& IROORZLQJ HPHUJHQFH IURP r& ZDWHU ,Q RQH DLUZDWHU WKHUPDO UHJLPH VQDNHV FRXOG EH IRXQG LQ HLWKHU DLU ZDWHU RU VXQ )LJ f 7KLV ZDV EHWZHHQ ZDWHU WHPSHUDWXUHV RI DSSUR[LPDWHO\ r& DQG r& DQG DLU WHPSHUDWXUHV RI r& DQG r& 7KHVH DUH HYLGHQWO\ WKH RQO\ ZDWHU WHPSHUDWXUHV DERYH r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n UHJXODWRU\ EHKDYLRU DQG WKH VSDUVHQHVV RI IROLDJH SHUPLWV DEXQGDQW

PAGE 56

DFFHVV WR VXQOLJKW $W VXFK WLPHV )LJ f WKH QXPEHU RI LQGLYLGXDOV EDVNLQJ XVXDOO\ SHDNV LQ ODWH PRUQLQJ DQG GHFOLQHV WKHUHDIWHU 7KHUH LV DQ LQGLYLGXDO WXUQRYHU DQG GXULQJ WKH DIWHUQRRQ VXEPHUJHQFH UDWH H[FHHGV HPHUJHQFH UDWH UHVXOWLQJ LQ D GHFUHDVH LQ WKH QXPEHU RI EDVNn LQJ LQGLYLGXDOV 7KH ILUVW LQGLYLGXDOV WR DWWDLQ 3%7 DQG HYHQWXDOO\ UHHQWHU WKH ZDWHU DUH SUREDEO\ WKH VPDOOHU DQLPDOV VLQFH WKH\ KHDW PRUH UDSLGO\ 'DWD WDNHQ RQ 0DUFK VXEVWDQWLDWH WKLV )LJ f %HWZHHQ DQG KRXUV WKHUH ZDV DQ LQYHUVH UHODWLRQVKLS EHn WZHHQ VL]H RI EDVNLQJ LQGLYLGXDOV DQG WKH ERG\DLU WHPSHUDWXUH GLIIHUHQWLDO 1R VXFK FRUUHODWLRQ H[LVWHG EHWZHHQ DQG KRXUV LQGLFDWLQJ WKDW WLPH RI HPHUJHQFH ZDV LQGHSHQGHQW RI ERG\ VL]H )LJXUH VKRZV WKH FKDQJHV LQ ERG\ WHPSHUDWXUH RI D 1DWUL[ WD[LVSLORWD DQG WKH DVVRFLDWHG HQYLURQPHQWDO WHPSHUDWXUHV XQGHU QDWXUDO FOLPDWLF FRQn GLWLRQV RI 1RYHPEHU DW /DNH $OLFH 'XULQJ WKH ZDUPHU PRQWKV PLG$SULO WKURXJK PLG2FWREHUf VXFK WKHUPRUHJXODWRU\ EHKDYLRU LV VHOGRP QHFHVVDU\ EHFDXVH DLU DQG ZDWHU WHPSHUDWXUHV GXULQJ WKH GD\ DUH XVXDOO\ ZLWKLQ WKH 3%7 RI WKLV VSHFLHV %HFDXVH RI WKH OHYHO DQG ZLGH UDQJH LQ 3%7 VQDNHV RFFDVLRQDOO\ ZHUH IRXQG WR EDVN LQ RQH ORFDWLRQ IURP WLPH RI HPHUJHQFH XQWLO HYHQLQJ VXEPHUJHQFH :DWHU WHPSHUDWXUHV GXULQJ WKHVH PRQWKV ZHUH RIWHQ ZLWKLQ WKH SUHIHUUHG UDQJH DQG PRVW VQDNHV HLWKHU UHPDLQHG LQ WKH ZDWHU RU KDG VXEPHUJHG E\ FHQVXV WLPH )LJ f (YHQLQJ 6XEPHUJHQFH :LWK WKH DSSURDFK RI QLJKWIDOO IHZ LI DQ\ VQDNHV UHPDLQ RQ EDVNLQJ VLWHV DERYH WKH ZDWHU )LJ f ,Q LQLWLDO ODERUDWRU\ H[SHULPHQWV ZKHUH OLJKWV FDPH RQ DW KRXUV DQG ZHQW RII DW KRXUV VQDNHV XVXDOO\ HPHUJHG ZLWKLQ DQ KRXU RI RQVHW RI OLJKWLQJ JLYHQ SURSHU WKHUPDO FRQGLWLRQVf DQG VXEPHUJHG ZLWKLQ WKH PLQXWH SHULRG DIWHU

PAGE 57

)LJXUH 7KH UHODWLRQVKLS EHWZHHQ ERG\ VL]H DQG ERG\DLU WHPSHUDWXUH GLIIHUHQWLDOV RI 1DWUL[ WD[LVSLORWD FROOHFWHG EHWZHHQ DQG KRXUV RQ 0DUFK

PAGE 58

727$/ /(1*7+ FPf %2'< 7(03(5$785( $,5 7(03(5$785( r&f r

PAGE 59

)LJXUH &KDQJHV LQ ERG\ WHPSHUDWXUH RI D 1DWUL[ WD[LVSLORWD WKHUPRUHJXODWLQJ XQGHU QDWXUDO FOLPDWLF FRQGLWLRQV RI 1RYHPEHU LQ H[SHULPHQWDO SHQ DW /DNH $OLFH VQDNH LQ ZDWHU > VQDNH LQ VKDGH VQDNH LQ VXQ

PAGE 60

'Rf IO/9G:

PAGE 61

OLJKW ZDV WHUPLQDWHG $IWHU VHYHUDO ZHHNV H[SRVXUH WR WKLV SKRWRSHULRG KRZHYHU VQDNHV RIWHQ HQWHUHG WKH ZDWHU DQ KRXU RU PRUH EHIRUH KRXUV 7KLV HYHQLQJ VXEPHUJHQFH DSSHDUV WR EH D WHPSHUDWXUHLQGHSHQGHQW UHVSRQVH WR GHFUHDVHG OLJKW VQDNHV VOLGH LQWR WKH ZDWHU UHJDUGOHVV RI WKH DLUZDWHU WHPSHUDWXUH GLIIHUHQWLDO %R\HU A QRWHG WKDW PRVW EDVNLQJ WXUWOHV OHIW WKHLU EDVNLQJ VLWHV DQG VXEPHUJHG SULRU WR PLQXWHV EHIRUH VXQVHW DOWKRXJK QR PHQWLRQ ZDV PDGH RI DLU DQG ZDWHU WHPSHUDWXUHV DW WKHVH WLPHV 6LQFH HYHQLQJ VXEPHUJHQFH LV HYLGHQWO\ FRPPRQ LQ PRVW VHPLDTXDWLF UHSWLOHV DQG VLQFH LW LV WHPSHUDWXUH LQGHSHQGHQW DW OHDVW LQ 1DWUL[ WD[LVSLORWDf WKLV UHVSRQVH SUREDEO\ UHSUHVHQWV D SUHGDWRU DYRLGDQFH EHKDYLRU &OHDUO\ PXFK IHHGLQJ DOPRVW H[FOXVLYHO\ RQ ILVK GRHV RFFXU DW WKLV WLPH ZKHQ ZDWHU WHPSHUDWXUHV SHUPLW EXW OLWWOH IHHGLQJ EHKDYLRU SUREDEO\ RFFXUV EHORZ D ZDWHU WHPSHUDWXUH DQG WKHUHIRUH ERG\ WHPSHUDWXUHf RI r& /XHWK f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r& WKURXJKRXW PRVW RI WKH \HDU 7KHUH DUH RWKHU HFRORJLFDOO\ UHOHYDQW IDFWRUV ZKLFK PD\ DOWHU WKH OHYHO RI SUHIHUUHG WHPSHUDWXUH DW OHDVW WHPSRUDULO\

PAGE 62

'LJHVWLRQ 6QDNHV DFFOLPDWHG WR r& ZHUH IHG ILVK FRQWDLQLQJ LQJHVWLEOH WUDQVPLWWHUV DQG ZHUH IRXQG WR UHJXODWH LQ D JUDGLHQWf DW D ZDUPHU HQG RI WKH QRUPDO UDQJH 7DEOH f 7KH VDPH SDWWHUQ ZDV IRXQG LQ DQLPDOV WKDW ZHUH JLYHQ DFFHVV WR D KHDW ODPS LQ DQ LVRWKHUPDO r&f HQYLURQPHQW 7ZR 1DWUL[ WD[LVSLORWD ZHUH IHG ILVK FRQWDLQLQJ WUDQVPLWWHUV DQG SHUPLWWHG WR WKHUPRUHJXODWH LQ WKLV HQYLURQPHQWDO FKDPEHU 7KH OHYHO RI DLU DQG ZDWHU WHPSHUDWXUHV ZDV ORZ HQRXJK WR LQGXFH EDVNLQJ EXW KLJK HQRXJK WR SHUPLW DWWDLQPHQW RI ERG\ WHPSHUDWXUHV LQ H[FHVV RI r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r& DQG F& :KHQ WKH\ ILUVW HPHUJHG WKH VQDNHV XVXDOO\ OD\ ZLWK WKH EROXV GLUHFWO\ XQGHU WKH VXQODPS DQG PRYHG WR D FRROHU DUHD DIWHU ERG\ WHPSHUDWXUH UHDFKHG r& WR r& $ IRXUGD\ WKHUPDO UHFRUG IRU RQH RI WKHVH VQDNHV LV VKRZQ LQ )LJ 7KHUPRSKLOLF UHVSRQVHV WR IHHGLQJ KDYH EHHQ UHSRUWHG IRU RWKHU UHSWLOHV 5HJDO %XVWDUG .LWFKHOO f LQFOXGLQJ WZR VHPLDTXDWLF VQDNHV 1DWUL[ VLSHGRQ DQG 7KDPQRSKLV VLUWDOLV ,Q DOO FDVHV WKH SUHIHUUHG WKHUPDO UDQJH IROORZLQJ IHHGLQJ VHHPV WR FRQn VWLWXWH D VXEUDQJH RI WKH SRVWDEVRUSWLYH 3%7 7KLV LQFUHDVH LQ SUHn FLVLRQ RI WKHUPRUHJXODWLRQ KDV LQ DOO FDVHV EHHQ LQWHUSUHWHG DV D IDFLOLWDWLRQ RI GLJHVWLYH SURFHVVHV

PAGE 63

)LJXUH )RXUGD\ ERG\ WHPSHUDWXUH UHFRUG RI D 1DWUL[ WD[LVSLORWD GLJHVWLQJ D ILVK HDWHQ RQ 0DUFK 7KURXJKRXW WKH ILUVW GD\ RI GLJHVWLRQ WKH VQDNH UHPDLQHG LQ WKH ZDWHU VHH WH[Wf WKH VXEVHTXHQW IRXUGD\ SHULRG LV VKRZQ $LU DQG ZDWHU WHPSHUDWXUH ZHUH PDLQWDLQHG DW r& 'DUN EDUV LQGLFDWH SHULRGV RI GDUNQHVV OLJKW EDUV LQGLFDWH SHULRGV RI OLJKW

PAGE 64

2'< 7(03(5$785( r&f +285

PAGE 65

7KH HIIHFW RI WHPSHUDWXUH RQ GLJHVWLYH HIILFLHQF\ ZDV GHWHUPLQHG IRU 1DWUL[ WD[LVSLORWD DW DQG r& 7KH JUHDWHVW H[WUDFWLRQ HIILFLHQF\ RFFXUUHG DW r& )LJ f DQG GHFUHDVHG ERWK DERYH DQG EHORZ WKLV WHPSHUDWXUH 7KLV WKHUPDO OHYHO FRUUHVSRQGV WR WKH SUHIHUUHG OHYHO IRU GLJHVWLRQ 7DEOH ,,f 5HJXUJLWDWLRQ RI IRRG ZDV YHU\ FRPPRQ DPRQJ VQDNHV PDLQWDLQHG DW r& DQRWKHU LQGLFDWLRQ WKDW WKLV ZDV VXSUDRSWLPDO WKHUPDO OHYHO IRU GLJHVWLRQ %HORZ r& GLJHVWLYH HIILFLHQF\ GHFUHDVHG ZLWK GHFUHDVLQJ WHPSHUDWXUH EXW WKH SHUFHQW HIILFLHQW\ OHYHO DW r& LV VWLOO D VXEVWDQWLDO ILJXUH ,W LV REYLRXV WKDW KLJK ERG\ WHPSHUDWXUHV H[SHGLWHG GLJHVWLRQ EXW ZHUH QRW DEVROXWHO\ QHFHVVDU\ LQGLFDWLQJ WKDW XQGHU QDWXUDO FRQGLWLRQV GLJHVWLYH SURFHVVHV ZRXOG FRQWLQXH DW QLJKW ZHOO DIWHU VXEPHUJHQFH LI ZDWHU WHPSHUDWXUH ZDV QRW H[FHVVLYHO\ FROG 7KLV ZLGH UDQJH RI GLJHVWLYH DFWLYLW\ LV SUREDEO\ QHFHVVDU\ LQ VXFK SRLNLORWKHUPV WR SUHYHQW SXWUHIDFWLRQ RI LQJHVWHG IRRG DW QLJKW DQG GXULQJ RWKHU SHULRGV ZKHQ ERG\ WHPSHUDWXUH IDOOV ZHOO EHORZ r& 3XWUHIDFWLRQ ZRXOG EH D SDUWLFXODUO\ JUHDW SUREOHP LQ VQDNHV VLQFH WKH\ LQJHVW LWHPV ZKROH DQG WKH LQWHUQDO WLVVXH RI LQn JHVWHG LWHPV ZRXOG QRW EH UHDFKHG E\ JDVWULF HQ]\PHV IRU PDQ\ KRXUV RU GD\V LI GLJHVWLRQ FHDVHG DW WHPSHUDWXUHV VOLJKWO\ EHORZ WKH RSWLPDO OHYHO 7KH LQIOXHQFH RI WHPSHUDWXUH RQ JDVWULF GLJHVWLRQ LQ WKH (XURSHDQ JUDVV VQDNH 1DWUL[ QDWUL[ ZDV VWXGLHG E\ 6NRF]\ODV f ZKR XVHG [UD\ SKRWRJUDSK\ WR GHWHUPLQH WKH VSHHG RI GLJHVWLRQ DW WHPSHUDWXUHV RI DQG r& +H IRXQG WKDW GLJHVWLRQ ZDV FRPSOHWHO\ DUUHVWHG DW r& DQG SURFHHGHG YHU\ VORZO\ RU HQGHG LQ UHJXUJLWDWLRQf DW r& 'LJHVWLRQ ZDV FRPSOHWH DW ERWK DQG r& EXW ZDV IDVWHU DW r& 'LJHVWLYH UDWHV LQ WKH NLQJ VQDNH /DPQURSHOWLV JHWXOXV ZHUH IRXQG E\ 5RRW f WR EH VLPLODU WR WKRVH RI 1 QDWUL[ EHORZ

PAGE 66

%2'< 7(03(5$785( r&f )LJXUH 7KH HIIHFW RI WHPSHUDWXUH RQ GLJHVWLYH H[WUDFWLRQ HIILFLHQF\ RI 1DWUL[ WD[LVSLORWD +RUL]RQWDO OLQH PHDQ YHUWLFDO EDU VWDQGDUG GHYLDWLRQ YHUWLFDO OLQH UDQJH

PAGE 67

7DEOH 3%7 5$1*( r&f 0($1 (IIHFW RI GLJHVWLRQ RQ WKH QRUPDO UDQJH RI SUHIHUUHG ERG\ WHPSHUDWXUHV 3267$%62537,9( ',*(67,1* 1 2%6f f f

PAGE 68

r& EXW WKH PD[LPXP GLJHVWLYH UDWH RFFXUUHG DW WKH KLJKHVW WHPSHUDWXUH HPSOR\HG r& 6NRF]\ODV DWWULEXWHG WKH GLVFUHSDQF\ LQ GLJHVWLYH UDWHV RI WKH WZR VSHFLHV DW r& WR LQWUDVSHFLILF GLIIHUHQFHV LQ 3%7 5HVHDUFK RQ GLJHVWLYH UDWHV RI RWKHU SRLNLORWKHUPV WHQGV WR VXEVWDQWLDWH WKLV JHQHUDOL]DWLRQ 0DQ\ IUHVKZDWHU ILVK DUH DEOH WR GLJHVW IRRG DW r& WR r& :DQJHQVWHHQ HW DO 0ROQDU DQG 7OJ f 7KHVH WHPSHUDWXUHV DUH EHORZ WKH ORZHU OLPLW RI WKH WKHUPDO DFWLYLW\ UDQJH RI 6SHQRGRQ SXQFWDWXV WKH ORZHVW NQRZQ IRU DQ\ UHSWLOH %RJHUW D Ef ,Q ILVK VWXGLHG RYHU D ZLGH UDQJH GLJHVWLYH UDWH DSSHDUV WR EH GLUHFWO\ FRUUHODWHG ZLWK ZDWHU WHPSHUDWXUH 5LGGOH f +RZHYHU WKH UDWH RI IRRG LQSXW PD\ DOVR LQIOXHQFH GLJHVWLYH HIILFLHQF\ 'DYLHV f IRXQG WKDW LQ &DUDVVLXV DXUDWXV WKH SURSHU OHYHO RI IRRG LQSXW FRXOG LQFUHDVH H[WUDFWLRQ HIILFLHQF\ WR SHUFHQW DW HLWKHU r& RU r& 2WKHU ZRUNHUV ,YOHY *HUNLQJ f KDYH IRXQG H[WUDFWLRQ HIILFLHQFLHV RI RWKHU ILVK DW D JLYHQ WHPSHUDWXUH WR EH LQGHSHQGHQW RI LQSXW UDWH $PSKLELDQV DOVR VKRZ ZLGH WKHUPDO UDQJHV IRU GLJHVWLRQ 3HJHO -RO\ 5RRW f DQG DUH FDSDEOH RI GLJHVWLQJ DW WHPSHUDWXUHV OHVV WKDQ r& OHYHOV DW ZKLFK SHULVWDOVLV FHDVHV LQ PRVW UHSWLOHV 6NRF]\ODV f 7KH SURFHVVHV RI JDVWULF GLJHVWLRQ DQG SHULVWDOVLV PD\ KDYH GLIIHUHQW WKHUPDO WKUHVKROGV DV LQ WKH SDLQWHG WXUWOH &OLU\VHP\V SLFWD ZKLFK FDQQRW GLJHVW EXW PDLQWDLQV SHULVWDOVLV DW r& )R[ DQG 0DVDFFKLD f 1RQKHOLRWKHUPLF SRLNLORWKHUPV WKHUHn IRUH VHHP WR KDYH ORZHU WKHUPDO WKUHVKROGV IRU GLJHVWLYH SURFHVVHV WKDQ KHOLRWKHUPLF VSHFLHV 2WKHU )DFWRUV $IIHFWLQJ 3UHIHUUHG %RG\ 7HPSHUDWXUH 5HJDO f FOHDUO\ GHPRQVWUDWHG WKDW VHYHUDO VSHFLHV RI OL]DUGV SODFHG LQ D JUDGLHQW ZLOO VHOHFW QLJKW WHPSHUDWXUHV WKDW DUH ZHOO EHn ORZ WKHLU SUHIHUUHG GLXUQDO 3(7 7KLV ZDV WUXH RI .ODXEHULQD ULYHUVLDQD

PAGE 69

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f VXJJHVW WKDW VQDNHV XQGHUJRLQJ HFG\VLV DFWLYHO\ VHOHFW ERG\ WHPSHUDWXUHV EHORZ WKHLU QRUPDO 3%7 7KH WKUHH VSHFLHV KH LQYHVWLJDWHG LQFOXGHG WZR VHPLDTXDWLF VSHFLHV 7KDPQRSKLV VLUWDOLV DQG 1DWUL[ VLSHGRQ 7KH ODWWHU ZKHQ QRW VKHGGLQJ KDG D 3%7 RI r& PHDQ VWDQGDUG GHYLDWLRQf EXW D SUHIHUHQFH RI r& ZKHQ XQGHUJRLQJ HFG\VLV ,Q WKH SUHVHQW VWXG\ WKHUH ZHUH QRW HQRXJK GDWD DYDLODEOH WR GHWHFW VXFK YROXQWDU\ K\SRWKHUPLF UHVSRQVH WR HFG\VLV EXW LQ YLHZ RI WKH XQDQLPLW\ RI .LWFKHOOnV GDWD IRU WKUHH VSHFLHV RI VQDNHV RQH FRQJHQHULF ZLWK 1 WD[LVSLORWD LW VHHPV OLNHO\ WKDW EURZQ ZDWHU VQDNHV KDYH ORZHU WKHUPDO SUHIHUHQGD ZKHQ VKHGGLQJ 1R SUHJQDQW IHPDOHV ZHUH XVHG LQ WKLV VWXG\ EXW GDWD IURP VHYHUDO VRXUFHV VXJJHVW WKDW VXFK LQGLYLGXDOV KDYH WKHUPDO SUHIHUHQFHV WKDW GLIIHU IURP WKRVH RI PDOHV DQG QRQSUHJQDQW IHPDOHV 6WHZDUW f IRXQG LQ 7KDPQRSKLV VLUWDOLV DQG 7 RUGLQRLGHV D FRQVLVWHQW WHQGHQF\ IRU SUHJQDQW IHPDOHV RI ERWK VSHFLHV WR PDLQWDLQ UHODWLYHO\ KLJK ERG\ WHPSHUDWXUHV )LWFK f IRXQG WKDW JUDYLG IHPDOH FRSSHUKHDGV $QFLVWURGRQ FRQWRUWUL[ UHJXODWHG ZLWKLQ PRUH SUHFLVH OLPLWV WKDQ PDOHV RU QRQSUHJQDQW IHPDOHV DQG QRWHG WKDW PRVW RI WKH FRSSHUKHDGV IRXQG EDVNLQJ LQ VXQVKLQH LQ VXPPHU ZHUH IHPDOHV 2VJRRG f IRXQG

PAGE 70

SUHJQDQW IHPDOH 1DWUL[ WD[LVSLORWD DQG 1 IDVHLDWD WR WKHUPRUHJXODWH ZLWKLQ D QDUURZHU WHPSHUDWXUH UDQJH WKDQ PDOHV RU QRQSUHJQDQW IHPDOHV EXW KLV VDPSOH IRU 1DWUL[ WD[LVSLORWD FRQVLVWHG RI RQO\ IRXU LQGLYLGXDOV WKUHH SUHJQDQW IHPDOHV RQH PDOHf ,Q DOO RI WKHVH DFFRXQWV WKH ERG\ WHPSHUDWXUHV IHOO ZLWKLQ WKH OLPLWV RI WKH QRUPDO 3%7 EXW FRQVWLWXWHG D VPDOOHU VXEUDQJH ZLWKLQ LW 7KH HIIHFW RI LQWUDVSHFLILF GLIIHUHQFHV LQ VL]H XSRQ 3%7 KDV EHHQ H[DPLQHG E\ VHYHUDO ZRUNHUV LQWHU DOLD %RJHUW f :LOKRIW f +LUWK f DQG %URRNV f 2QO\ LQ %DVLOLVFXV YLWWDWXV 0LUWK f ZHUH VWDWLVWLFDOO\ VLJQLILFDQW GLIIHUHQFHV IRXQG DQG WKH GLIIHUHQFHV ZHUH VR VOLJKW r& LQ MXYHQLOHV r& LQ DGXOWVf WKDW HFRORJLFDO VLJQLILFDQFH FDQQRW EH DVFULEHG 7KH PRVW OLNHO\ FDQGLGDWH IRU DQ HFRORJLFDOO\ VLJQLILFDQW FKDQJH LQ 3%7 ZLWK VL]H LV SUREDEO\ 9DUDQXV NRPRGRHQVLV WKH ZRUOGnV ODUJHVW OL]DUG 7KLV VSHFLHV LV DUERUHDO DV D MXYHQLOH DQG EHFRPHV WHUUHVWULDO XSRQ DWWDLQLQJ WKH OHQJWK RI WR PHWHUV :DOWHU $XIIHQEHUJ SULYDWH FRPPXQLFDWLRQf ,W ZRXOG EH VXUSULVLQJ LI D FKDQJH LQ 3%7 GLG QRW DFFRPSDQ\ WKLV FKDQJH LQ KDELWDW SUHIHUHQFH 7KH 3%7 LQ D JLYHQ VSHFLHV RI UHSWLOH WKHQ LV QRW DQ LPPXWDEOH WKHUPDO OHYHO ,W PD\ XQGHUJR WHPSRUDO FKDQJHV DQG FKDQJHV UHIOHFWLQJ WKH WKHUPDO RSWLPD IRU YDULRXV SK\VLRORJLFDO SURFHVVHV ,W KDV ORQJ EHHQ NQRZQ WKDW VQDNHV XQGHUJRLQJ HFG\VLF SURFHVVHV UHIXVH WR IHHG 7KLV EHKDYLRU SDWWHUQ KDV EHHQ LQWHUSUHWHG DV D UHVSRQVH WR DYRLG GDPDJH WR WKH QHZO\ GHYHORSLQJ HSLGHUPDO OD\HU ZKLFK ZRXOG EH VHYHUHO\ VWUHWFKHG RU HYHQ VSOLW E\ WKH LQJHVWLRQ RI ODUJH LWHPV 7KH SUHn FHGLQJ GLVFXVVLRQ RI WKH WKHUPDO UHTXLUHPHQWV RI WKHVH WZR SURFHVVHV HHG\VLV DQG GLJHVWLRQf LQ UHSWLOHV VXJJHVWV D WKHUPDO LQFRPSDWLELOLW\ DQG FHUWDLQO\ SUHVHQWV DW OHDVW DV VWURQJ DQ DUJXPHQW IRU WKHLU QRQn FRQFXUUHQFH

PAGE 71

7KH (FRORJLFDO 6LJQLILFDQFH RI 5HSWLOLDQ 3UHIHUUHG %RG\ 7HPSHUDWXUH 0DQ\ ZRUNHUV 5XLEDO %UDWWVWURP .LWFKHOO 6NRF]\ODV f KDYH FRPPHQWHG RQ WKH HPSLULFDO UHODWLRQVKLS EHn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n WKH OHYHO RI 3%7 7KH WKHUPDO H[WUHPHV EHWZHHQ ZKLFK UHSWLOHV PXVW OLYH DUH WKH DSSUR[LPDWH OHYHOV WKDW IUHH]H WKHLU WLVVXHV DQG WKRVH WKDW GHQDWXUH WKHLU SURWHLQV RU LQ RWKHU ZD\V FDXVH SK\VLRORJLFDO KHDWGHDWK %XW PRVW LI QRW DOO UHSWLOHV NHHS WKHLU ERG\ WHPSHUDWXUH IURP YDU\LQJ ZLWK HQYLURQPHQWDO WHPSHUDWXUH E\ PDLQWDLQLQJ LW DW D FHUWDLQ OHYHO ZLWKLQ WKLV r& VSDQ (YROXWLRQDULO\ UHSWLOHV FDQ FKRRVH WKH FHLOLQJ RI WKHLU SUHIHUUHG UDQJH E\ EHKDYLRUDOO\ XWLOL]LQJ VRODU HQHUJ\ (PSLULFDO HYLGHQFH RI WKLV LV WKH RFFXSDWLRQ E\ VHYHUDO VSHFLHV RI UHSWLOHV ZLWK GLIIHUHQW 3%7V RI D FRPPRQ KDELWDW &RZOHV DQG %RJHUW %RJHUW 6RXOHf +RZHYHU WKH WKHUPDO FKDUDFWHULVWLFV RI WKH HQYLURQPHQW OHDYH OHVV HYROXWLRQDU\ FKRLFH LQ WKH ORZHU WKUHVKROG RI WKH 367 EHFDXVH UHSWLOHV ODFN WKH FRROLQJ PHFKDQLVPV FKDUDFWHULVWLF RI PRVW PDPPDOV DQG ELUGV 6FKPLGW1LHOVHQ DQG 'DZVRQ f DQG FDQ WKHUHIRUH FRRO RQO\ WR WKH OHYHO RI WKH FRROHVW VHJPHQW RI WKHLU HQYLURQn PHQW 6XPPHU VKDGH WHPSHUDWXUHV LQ 1RUWK $PHULFD VHW WKLV ORZHU XWLOL]DEOH

PAGE 72

R R OHYHO DW DERXW & WR & IRU GLXUQDOO\DFWLYH WHUUHVWULDO UHSWLOHV 7KXV WKH REVHUYDWLRQ WKDW 3%7 LV JHQHUDOO\ FORVHU WR WKH FULWLFDO WKHUPDO PD[LPXP WKDQ WR WKH FULWLFDO WKHUPDO PLQLPXP LV WR EH H[SHFWHG EHFDXVH WKH WKHUPDO UDQJH EHWZHHQ FULWLFDO WKHUPDO PLQLPXP DQG r& LV XQDYDLODEOH +RZHYHU PDQ\ GLXUQDO UHSWLOHV RSHUDWH DW WKHUPDO OHYHOV RQO\ D IHZ GHJUHHV EHORZ WHPSHUDWXUHV WKDW FDXVH LUUHYHUVLEOH WLVVXH GDPDJH 7KH TXHVWLRQ WKHUHIRUH EHFRPHV ZK\ GR QRW DOO GLXUQDOO\ DFWLYH UHSWLOHV FKRRVH 3%7V RI DERXW r& DQG OHDYH PDUJLQV RI VDIHW\ DW ERWK HQGV" 7KH DQVZHU LV DSSDUHQWO\ UHODWHG WR f WKH ELRORJLFDO HIIHFWV RI WKHUPDO H[WUHPHV DQG f WKH FRUUHODWLRQ EHWZHHQ 3%7 DQG WKH FULWLFDO WKHUPDO PD[LPXP +\SRWKHUPLD VORZV WKH UDWHV RI SK\VLRORJLFDO SURFHVVHV EXW UDUHO\ FDXVHV LUUHYHUVLEOH GDPDJH DERYH r& +RZHYHU LUUHYHUVLEOH WLVVXH GDPDJH LV LQFXUUHG DW WHPSHUDWXUHV DERYH DERXW r& 7KHVH WHPSHUDWXUHV VOLJKWO\ H[FHHG WKH KLJKHVW DLU WHPSHUDWXUH WKRXJK FHUWDLQO\ QRW WKH KLJKHVW EODFNEXOE WHPSHUDWXUHf WR ZKLFK D GLXUQDO DQLPDO FRXOG H[SHFW WR EH H[SRVHG LQ LWV QRUPDO DFWLYLW\ DQG QDWXUDO KDELWDW 7KHUH LV D GLUHFW FRUUHODWLRQ EHWZHHQ WKH SUHIHUUHG OHYHO RI ERG\ WHPSHUDWXUH DQG WKH OHYHO RI FULWLFDO WKHUPDO PD[LPXP 6FKPLGW1LHOVHQ DQG 'DZVRQ %UDWWVWURP VHH )LJ f 7KH KLJKHVW ERG\ WHPSHUDWXUH D UHSWLOH ZLOO HYHU DWWDLQ PXVW EH EHORZ WKH &70D[ LI WKDW DQLPDO LV WR VXUYLYH DQG WKLV ERG\ WHPSHUDWXUH VKRXOG EH GLUHFWO\ UHODWHG WR WKH KLJKHVW DLU WHPSHUDWXUH H[SHULHQFHG 7KHVH HQYLURQPHQWDO WKHUPDO H[WUHPHV DUH A7KH WKHUPDO SRLQW DW ZKLFK ORFRPRWRU\ DFWLYLW\ EHFRPHV GLVn RUJDQL]HG DQG WKH DQLPDO ORVHV LWV DELOLW\ WR HVFDSH IURP FRQGLWLRQV WKDW ZLOO SURPSWO\ OHDG WR LWV GHDWK &RZOHV DQG %RJHUW f 7KH WHPSHUDWXUH WKDW FDXVHV D FROG QDUFRVLV DQG HIIHFWXDOO\ SUHYHQWV ORFRPRWLRQ &RZOHV DQG %RJHUW f

PAGE 73

7KH UHODWLRQVKLS EHWZHHQ SUHIHUUHG ERG\ WHPSHUDWXUH DQG FULWLFDO WKHUPDO PD[LPXP LQ UHSWLOHV [ f 'DWD DUH IURP %UDWWVWURP f IRU VSHFLHV ZLWK VDPSOH VL]HV RI )LJXUH

PAGE 75

VHOHFWLYH IDFWRUV ZKLFK VHW WKH OHYHO RI &70D[ E\ HOLPLQDWLQJ WKH LQGLYLGXDOV ZLWK ORZHVW WKHUPDO WROHUDQFH 6LQFH &70D[ EHDUV D UHn ODWLRQVKLS WR 3%7 WKDW LV DSSDUHQWO\ JHQHWLFDOO\ IL[HG WKHUH VKRXOG EH D GLUHFW FRUUHODWLRQ EHWZHHQ WKHVH HQYLURQPHQWDO H[WUHPHV DQG 3%7 )XUWKHUPRUH WKH 3%7 RI D UHSWLOH VKRXOG EH PRUH VWURQJO\ FRUUHODWHG ZLWK WKH KLJKHVW WHPSHUDWXUH UHFRUGHG LQ LWV KDELWDW WKDQ ZLWK DQ\ PHDQ KLJK WHPSHUDWXUH YDOXH EHFDXVH WKH ODWWHU DUH FOHDUO\ RI OHVV HYROXWLRQDU\ VLJQLILFDQFH LQ IL[LQJ WKH OHYHO RI &70D[ )LJXUH VKRZV WKH KLJK FRUUHODWLRQ U f EHWZHHQ 3%7 LQ VHYHUDO SULPDULO\ KHOLRWKHUPLF VSHFLHV RI UHSWLOHV DQG WKH KLJKHVW WHPSHUDWXUH HYHU UHFRUGHG DW WKH ZHDWKHU VWDWLRQ QHDUHVW WKH FROOHFWLRQ ORFDOLW\ .LQFHU f 6WXGLHV WKDW IDLOHG WR OLVW FROOHFWLQJ ORFDOLW\ RU IRU ZKLFK QR VXFK ZHDWKHU GDWD FRXOG EH IRXQG DUH H[FOXGHG 'DWD IURP VWXGLHV LQ ZKLFK ILHOG ERG\ WHPSHUDWXUHV FRQVWLWXWHG WKH EDVLV IRU GHWHUPLQDWLRQ ZHUH LQFOXGHG RQO\ LI WKH VDPSOH VL]H H[FHHGHG DQG REVHUYDWLRQDO FRUUHODWLRQV ZHUH PDGH :KHQ WKHVH FRQGLWLRQV DUH PHW 3%7 DQG PHDQ ERG\ WHPSHUDWXUH 3HWHUV f EHFRPH V\QRQ\PRXV DQG FRPSDULVRQ EHWZHHQ WKHVH YDOXHV LV YDOLG 7KH SHUWLQHQW VWDWLVWLFDO GDWD DQG UHIHUHQFHV DUH OLVWHG LQ 7DEOH $V H[SHFWHG WKH FRUUHODWLRQ ZLWK 3%7 LV VLJQLILFDQWO\ JUHDWHU IRU PD[LPXP WHPSHUDWXUH WKDQ IRU WKH PHDQ WHPSHUDWXUH RI WKH KRWWHVW PRQWK -XO\ LQ WKH QRUWKHUQ KHPLVSKHUH -DQXDU\ LQ WKH VRXWKHUQf 7KLV VXSSRUWV WKH K\SRWKHVLV WKDW WKH OHYHO RI 3%7 LV LQGLUHFWO\ IL[HG HYROXWLRQDULO\ E\ LWV UHODWLRQVKLS WR WKH OHYHO RI &70D[ ZKLFK LV GLUHFWO\ IL[HG E\ KLJK HQYLURQPHQWDO WHPSHUDWXUH H[WUHPHV 7KLV GRHV $ SULPDU\ KHOLRWKHUP LV KHUH GHILQHG DV D GLXUQDOO\DFWLYH OL]DUG LQKDELWLQJ DQ RSHQ KDELWDW RU KDELWDWVf WKDW RIIHU DFFHVV WR VXQOLJKW WKURXJKRXW WKH GD\

PAGE 76

)LJXUH 5HODWLRQVKLS EHWZHHQ SUHIHUUHG ERG\ WHPSHUDWXUH RI SULPDU\ KHOLRWKHUPV DQG WKH KLJKHVW DLU WHPSHUDWXUH UHFRUGHG LQ WKH DUHD IURP ZKLFK WKH\ ZHUH FROOHFWHG 6WDWLVWLFDO LQIRUPDWLRQ DQG VRXUFHV IRU WKH GDWD DUH OLVWHG LQ 7DEOH

PAGE 77

35()(55(' %2'< 7(03(5$785( r&f 21

PAGE 78

7DEOH 'DWD IRU SRLQWV SORWWHG LQ )LJXUH IRU SULPDU\ KHOLRWKHUPLF OL]DUGV 180%(5 ,1 ),* 63(&,(6 1 3%7 6285&( $QROLV DOOLVRQL 5XLEDO $QROLV KRPROHFKLV 5XLEDO $QROLV VDJUHL 5XLEDO &URWDSK\WXV FROODULV )LWFK 'LSVRVDXUXV GRUVDOLV 0r 'H:LWW E 6DXURPDOXV REHVXV &RZOHV DQG %RJHUW 6FHORSRUXV JUDFLRVXV 0XHOOHU 6FHORSRUXV RFFLGHQWDOLV /DUVRQ 6FHORSRUXV RUFXWWL 0D\KHZ 8URVDXUXV RUQDWXV %UDWWVWURP &QHPLGRSKRUXV VH[OLQHDWXV 0r )LWFK 6FHORSRUXV ZRRGL %RJHUW &QHPLGRSKRUXV WHVVHODWXV %RJHUW $PSKLERORUXV EDUEDWXV /HH DQG %DGKDP $PSKLERORUXV LQHUPLV 0 3LDQND 0$;,080 7(03 0($1 +,*+ 7(03 &255(/$7,21 &2()),&,(17 (48$7,21 )25 /,1( < ; f§ f‘PDQ\

PAGE 79

QRW PHDQ KRZHYHU WKDW WKH DEVROXWH OHYHO RI 3%7 LV VROHO\ D IXQFWLRQ RI KLJK DLU WHPSHUDWXUH H[WUHPHV $Q\ VSHFLHVVSHFLILF EHKDYLRU EXUURZLQJ SDQWLQJ HWFf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nPHWDEROLF HIILFLHQF\n DW QRQRSWLPDO WHPSHUDWXUHV $W ERG\ WHPSHUDWXUHV EHORZ 3%7 PHWDEROLVP PHUHO\ VORZV GRZQ DV D IXQFWLRQ RI WHPSHUDWXUH )LJ f DQG QRUPDO DFWLYLW\ VXFK DV IRRG SURFXUHPHQW FHDVHV %XW DW VXFK WLPHV WKH DQLPDO LQFXUV QR WLVVXH GDPDJH DQG WKH GHFUHDVHG OHYHO RI PHWDEROLVP LV FRPSDWLEOH ZLWK GHFUHDVHG GLJHVWLYH HIILFLHQF\ DQG WKHUHIRUH HQHUJ\ DYDLODELOLW\f DQG IRRG FRQVXPSWLRQ $W WHPSHUDWXUHV DERYH 3%7 KRZHYHU WKH GHFUHDVHG OHYHOV RI GLJHVWLYH HIILFLHQF\ DQG PHWDEROLF HIILFLHQF\ JHQHUDOO\f DQG IRRG FRQVXPSWLRQ FRLQFLGH Z7LWK DQ LQFUHDVH LQ PHWDEROLVP ,Q DGGLWLRQ YHU\ KLJK WHPSHUDWXUHV ZLOO FDXVH LUUHYHUVLEOH WLVVXH GDPDJH 6R E\ FKRRVLQJ UHODWLYHO\ KLJK ERG\ WHPSHUDWXUHV KHOLRWOLHUPLF UHSWLOHV DYRLG WKH SUREOHP RI RYHUKHDWLQJ DQG DUH SHQDOL]HG E\ KDYLQJ WR UHPDLQ LQDFWLYH RU VXERSWLPDOO\ DFWLYH RQFRRO GD\V 7KH RSSRVLWH VWUDWHJ\ RI FKRRVLQJ D ORZ 3%7 WR LQVXUH PRUH GD\V RI DFWLYLW\ HQWDLOV WKH ULVN RI RYHUn KHDWLQJ WR WKH SRLQW RI GHDWK 7KLV DV PHQWLRQHG LV SUREDEO\ WKH PHFKDQLVP WKDW VHWV WKH OHYHO RI UHSWLOLDQ 3%7 HYROXWLRQDULO\ +LJK WKHUPDO H[WUHPHV ZLOO HOLPLQDWH WKH OHDVW KHDW WROHUDQW ORZHVW &70D[f

PAGE 80

)LJXUH 7KH HIIHFW RI WHPSHUDWXUH RQ WKH PHWDEROLF UDWH RI D J 1DWUL[ WD[LVSLORWD DW WZR DFFOLPDWLRQ WHPSHUDWXUHV $f r DQG %f r

PAGE 81

%2'< 7(03(5$785( r&f 0(7$%2/,60 FFKUf =/

PAGE 82

LQGLYLGXDOV DQG VHOHFW IRU D VSHFLHV ZLWK D KLJKHU &70D[ DQG 3%7f 7KHRUHWLFDOO\ D UHSWLOHnV &70D[ VKRXOG EH MXVW DERYH WKH KLJKHVW DPELHQW WHPSHUDWXUH DQG ERG\ WHPSHUDWXUHf WKH VSHFLHV HYHU HQFRXQWHUHG LQ LWV QRUPDO KDELWDW GXULQJ LWV QRUPDO SHULRG RI DFWLYLW\ 7KHUHIRUH GLXUQDO WHUUHVWULDO VSHFLHV VKRXOG KDYH KLJKHU 3%7V WKDQ QRFWXUQDO WHUUHVWULDO VSHFLHV 6WLOO WKH KLJKHVW GD\WLPH DLU WHPSHUDWXUH UHFRUGHG LQ DQ DUHD VKRXOG EH FRUUHODWHG ZLWK WKH KLJKHVW QLJKW WHPSHUDWXUH $ FRUUHODWLRQ WKHQ GRHV H[LVW EHWZHHQ 3%7 RI QRFWXUQDO UHSWLOHV DQG KLJKHVW DLU WHPSHUDWXUH )LJ f 7KH FRUUHODWLRQ LV ZHDNHU WKDQ ZLWK SULPDULO\ KHOLRWKHUPLF VSHFLHV DV ZRXOG EH H[SHFWHG %HWZHHQ WKH OLQHV UHODWLQJ 3%7 ZLWK KLJKHVW DLU WHPSHUDWXUH LQ SULPDU\ KHOLRWKHUPLF VSHFLHV DQG LQ QRFWXUQDO VSHFLHV WKHUH DUH D VHULHV RI SRLQWV ZKLFK IRUP D WKLUG OLQH ZLWK DQ LQWHUPHGLDWH VORSH 7KH SRLQWV DUH IRU GLXUQDOO\DFWLYH VQDNHV DQG IRUHVW OL]DUGV 7KH OL]DUGV $QROLV DQG (XPHFHVf EDVN LQ SDWFKHV RI VXQOLJKW UHDFKLQJ WKH IRUHVW IORRUf EXW QRW QHDUO\ DV H[WHQVLYHO\ DV SULPDU\ KHOLRWKHUPLF VSHFLHV +RZHYHU WKH KHOLRWKHUPLF VQDNHV &ROXEHU DQG +HWHURGRQf RFFXU LQ WKH VDPH RSHQ KDELWDWV LQ ZKLFK KHOLRWKHUPLF OL]DUGV PDLQWDLQ KLJKHU 3%7V 7KLV VXJJHVWV WKDW WKH GLIIHUHQFHV LQ WKHUPDO SUHIHUHQGD RI VQDNHV DQG OL]DUGV PD\ EH D IXQFWLRQ RI GLIIHUHQFHV LQ WKH HFRORJ\ RI WKH WZR JURXSV 7KH QRFWXUQDO VSHFLHV XVHG WR GHWHUPLQH OLQH $ )LJ f ZHUH ZLWK RQH H[FHSWLRQ WKH *LOD PRQVWHU +HORGHUPD VXVSHFWXPf DOO VQDNHV VR LW LV LPSRVVLEOH WR GHWHUPLQH IURP WKHVH GDWD ZKHWKHU WKHLU ORZHU WKHUPDO SUHIHUHQGD H[LVW EHFDXVH WKH\ DUH QRFWXUQDO RU EHFDXVH WKH\ DUH VQDNHV RU ERWK 2QH FRQVLVWHQW FKDUDFWHULVWLF RI VQDNHV WKDW VHSDUDWHV WKHP IURP DOPRVW DOO OL]DUGV VXJJHVWV D EDVLV IRU D ORZHU 3%7 7KLV LV WKH DEVHQFH RI OHJV 7KH WKHUPRUHJXODWRU\ VLJQLILFDQFH RI WKLV LV WKDW

PAGE 83

35()(55(' %2'< 7(03(5$785( r&f )LJXUH 5HODWLRQVKLS EHWZHHQ UHSWLOLDQ SUHIHUUHG ERG\ WHPSHUDWXUH DQG WKH KLJKHVW DLU WHPSHUDWXUH UHn FRUGHG LQ WKH FROOHFWLRQ DUHD $ QRFWXUQDO UHSWLOHV FLUFOHVf % GLXUQDO VQDNHV DQG IRUHVW OL]DUGV VTXDUHV & SULPDU\ KHOLRWKHUPLF OL]DUGV IURP )LJXUH f 6WDWLVWLFDO LQIRUPDWLRQ DQG VRXUFHV IRU GDWD DUH OLVWHG LQ 7DEOH OLQH $f DQG 7DEOH OLQH %f

PAGE 84

7DEOH 'DWD IRU QRFWXUQDO SRLQWV SORWWHG UHSWLOHV OLQH LQ )LJ $f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

PAGE 85

7DEOH 'DWD IRU SRLQWV SORWWHG LQ )LJXUH IRU GLXUQDO VQDNHV DQG IRUHVW OL]DUGV OLQH %f 180%(5 ,1 ),* 63(&,(6 1 3%7 6285&( $QROLV DOORJXV 5XLEDO $QROLV OXFLXV 5XLEDO (XPHFHV IDVFLDWXV )LWFK (XPHFHV REVROHWXV 0 )LWFK &ROXEHU FRQVWULFWRU )LWFK &ROXEHU FRQVWULFWRU .LWFKHOO +HWHURGRQ SODW\UKLQRV .LWFKHOO 0$;,080 7(03 0($1 +,*+ 7(03 &255(/$7,21 &2()),&,(17 (48$7,21 )25 /,1( < ; I

PAGE 86

WHUUHVWULDO VQDNHV DUH LQ PRUH LQWLPDWH SK\VLFDO FRQWDFW ZLWK WKHLU HQYLURQPHQW DQG PRUH YXOQHUDEOH WR FRQGXFWLYH KHDW H[FKDQJH ZLWK WKH VXEVWUDWH 7KLV LQ SDUW H[SODLQV ZK\ &DUSHQWHU f LQ KLV VWXG\ RI WKHUPRUHJXODWLRQ LQ WKUHH VSHFLHV RI JDUWHU VQDNHV IRXQG FORDFDO WHPSHUDWXUHV WR EH PRUH FORVHO\ FRUUHODWHG ZLWK WKH WHPSHUDWXUH DW WKH JURXQG VXUIDFH WKDQ ZLWK DLU WHPSHUDWXUH DERYH RU VRLO WHPSHUDWXUH EHORZ 'HVHUW OL]DUGV UHO\ JUHDWO\ RQ VXFK FRQGXFWLYH KHDW H[FKDQJH DV D FRROLQJ PHFKDQLVP 7KH GHVHUW LJXDQD 'LSVRVDXUXV GRUVDOLV SUHVVHV LWV YHQWHU IURP VLGH WR VLGH LQ WKH VDQG H[SRVLQJ FRROHU OD\HUV WR ZKLFK LW ORVHV ERG\ KHDW E\ FRQGXFWLRQ 1RUULV f $W KLJKHU WHPSHUDWXUHV OL]DUGV UHWUHDW WR EXUURZV 'H:LWW D E 0F*LQQLV 1RUULV f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f ZLWK GLXUQDO VQDNHV 7KH RQO\ GDWD DYDLODEOH IRU VXFK OL]DUGV DUH IRU WKH VSHFLHV 2SKLVDXUXV DWWHQXDWXV )LWFK f LQ .DQVDV )LHOG WHPSHUDWXUHV RI DFWLYH LQGLYLGXDOV FROOHFWHG RQ FOHDU GD\V UDQJHG EHWZHHQ r& DQG r& 7KH PHDQ YDOXH RI r& ZRXOG IDOO r& EHORZ WKH GLXUQDO VQDNHIRUHVW OL]DUG OLQH 7KLV LV JRRG DJUHHPHQW HYHQ WKRXJK WKLV SRLQW ZDV EDVHG RQ D VDPSOH VL]H WRR VPDOO WR ZDUUDQW LWV LQFOXVLRQ LQ )LJ

PAGE 87

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n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

PAGE 88

%URZQ ZDWHU VQDNHV GLJHVWLQJ IRRG WKHUPRUHJXODWH DW D VXEOHYHO ZLWKLQ WKH QRUPDO SUHIHUUHG ERG\ WHPSHUDWXUH UDQJH 'LJHVWLYH HIILFLHQF\ LV JUHDWHVW DW DERXW r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

PAGE 89

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

PAGE 90

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f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f +DQGERRN RI 3K\VLRORJ\ 6HFW $GDSWDWLRQ WR WKH HQYLURQPHQW $PHU 3K\AVLRO 6RF :DVKLQJWRQ & )U\ ) ( 6 +DUW DQG ) :DONHU /HWKDO WHPSHUDWXUH UHODWLRQV IRU D VDPSOH RI \RXQJ VSHFNOHG WURXW 6DOYHOLQXV IURQWLQDOLVf 8QLY 7RURQWR 6WXG %LRO

PAGE 91

*HUNLQJ 6 ,QIOXHQFH RI UDWH RI IHHGLQJ RQ ERG\ FRPSRVLWLRQ DQG SURWHLQ PHWDEROLVP RI EOXHJLOO VXQILVK 3K\VLRORJLFDO =RRORJ\ +HDWK ( 7HPSHUDWXUH UHJXODWLRQ DQG GLXUQDO DFWLYLW\ LQ KRUQHG OL]DUGV 8QLY &DOLI 3XEO =RRO +HDWK : 7KHUPRSHULRGLVP LQ VHDUXQ FXWWKURDW WURXW 6DOPR FODUNL FODUNLf 6FLHQFH +LUWK + ) 7KH HFRORJ\ RI WZR OL]DUGV RQ D WURSLFDO EHDFK (FRORJLFDO 0RQRJUDSKV +XWFKLVRQ 9LFWRU + +HUQGRQ 'RZOLQJ DQG $OOHQ 9LQHJDU 7KHUPRUHJXODWLRQ LQ D EURRGLQJ IHPDOH ,QGLDQ S\WKRQ 3\WKRQ PROXUXV ELYLWWDWXV 6FLHQFH +XWFKLVRQ 9LFWRU + DQG 0LFKDHO 5 )HUUDQFH 7KHUPDO WROHUDQFHV RI 5DQD SLSLHQV DFFOLPDWHG WR GDLO\ WHPSHUDWXUH F\FOHV +HUSHWRORJLFD ,YOHY 9 6 %DODQFH RI HQHUJ\ LQ FDUSV =RRO =K -RO\ ,QIOXHQFH GHV EDVVHV WHPSHUDWXUHV VXU F\FOH DOLPHQWDLUH GH TXHOTXHV WULWRQV )UDQM£LV %XOO 6RF =RRO )U .LQFHU % &OLPDWH DQG ZHDWKHU GDWD IRU WKH 8QLWHG 6WDWHV
PAGE 92

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f LQ
PAGE 93

5RRW + *DVWULF GLJHVWLRQ ZLWK K\SRWKHUPLD REVHUYDWLRQV DQG DSSOLFDWLRQV 7KHVLV 8QLYHUVLW\ RI 0LQQHVRWD 5XLEDO 5RGROIR 7KHUPDO UHODWLRQV RI ILYH VSHFLHV RI WURSLFDO OL]DUGV (YROXWLRQ 6FKPLGW1LHOVHQ .QXW DQG :LOOLDP 5 'DZVRQ 7HUUHVWULDO DQLPDOV LQ GUM KHDW GHVHUW UHSWLOHV ,Q % 'LOO HGf +DQGERRN RI 3K\VLRORJ\ 6HFW $GDSWDWLRQ WR WKH (QYLURQPHQW $PHU 3K\VLRO 6RF :DVKLQJWRQ & 6NRF]\ODV 5DID ,QIOXHQFH RI WHPSHUDWXUH RQ JDVWULF GLJHVWLRQ LQ WKH JUDVV VQDNH 1DWUL[ QDWUL[ / &RPS %LRFKHP 3K\VLRO 6RXOH 0LFKDHO $VSHFWV RI WKHUPRUHJXODWLRQ LQ QLQH VSHFLHV RI OL]DUGV IURP %DMD &DOLIRUQLD &RSHLD 6WHZDUW *OHQQ 5 7KHUPDO HFRORJ\ RI WKH JDUWHU VQDNHV 7KDPQRSKLV VLUWDOLV FRQFLQQXV +DOORZHOOf DQG 7KDPQRSKLV RUGLQRLGHV %DLUG DQG *LUDUGf +HUSHWRORJLFD :DQJHQVWHHQ + + 5RRW & % -HQVRQr ,PDPRJOX DQG 3 $ 6DOPRQ 'HSUHVVLRQ RI JDVWULF VHFUHWLRQ DQG GLJHVWLRQ E\ JDVWULF K\SRn WKHUPLD ,WV FOLQLFDO XVH LQ PDVVLYH KHPDWRPHVLV 6XUJHU\ :HDWKHUV :HVOH\ : 3K\VLRORJLFDO WKHUPRUHJXODWLRQ LQ WKH OL]DUG 'LSVRVDXUXV GRUVDOLV &RSHLD :LOKRIW & 2EVHUYDWLRQV RQ SUHIHUUHG ERG\ WHPSHUDWXUHV DQG IHHGLQJ KDELWV RI VRPH VHOHFWHG WURSLFDO LJXDQDV +HUSHWRORJLFD :LOKRIW & DQG $QGHUVRQ (IIHFW RI DFFOLPDWLRQ RQ WKH SUHIHUUHG ERG\ WHPSHUDWXUH RI WKH OL]DUG 6FHORSRUXV RFFLGHQWDOLV 6FLHQFH

PAGE 94

%,2*5$3+,&$/ 6.(7&+ 'RQDOG (XJHQH *RRGPDQ ZDV ERUQ -DQXDU\ DW .HQQHWW 0LVVRXUL ,Q -XQH KH UHFHLYHG WKH GHJUHH RI %DFKHORU RI $UWV ZLWK D PDMRU LQ =RRORJ\ IURP WKH 8QLYHUVLW\ RI 0LVVRXUL ,Q KH HQUROOHG LQ WKH *UDGXDWH 6FKRRO RI WKH 8QLYHUVLW\ RI )ORULGD DQG KDV XQWLO WKH SLnHVHQW WLPH SXUVXHG KLV ZRUN WRZDUG WKH GHJUHH RI 'RFWRU RI 3KLORVRSK\ LQ WKH 'HSDUWPHQW RI =RRORJ\ 'RQDOG (XJHQH *RRGPDQ LV D PHPEHU RI WKH $PHULFDQ 6RFLHW\ RI ,FKWK\RORJLVWV DQG +HUSHWRORJLVWV DQG WKH $PHULFDQ $VVRFLDWLRQ IRU WKH $GYDQFHPHQW IRU 6FLHQFH

PAGE 95

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

PAGE 96

7KLV GLVVHUWDWLRQ ZDV VXEPLWWHG WR WKH 'HDQ RI WKH &ROOHJH RI $UWV DQG 6FLHQFHV DQG WR WKH *UDGXDWH &RXQFLO DQG ZDV DFFHSWHG DV SDUWLDO IXOILOOPHQW RI WKH UHTXLUHPHQWV IRU WKH GHJUHH RI 'RFWRU RI 3KLORVRSK\ -XQH 'HDQ *UDGXDWH 6FKRRO

PAGE 97

81,9(56,7< 2) )/25,'$ P QL LQQ LQ}


6
UNIVERSITY OF FLORIDA
I m ni inn in -
3 1262 08556 7401