GROWTH AND SURVIVAL RATES OF WILD AND REPATRIATED HATCHLING
AMERICAN ALLIGATORS (Alligator mississippiensis) IN CENTRAL FLORIDA
A THESIS PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE
UNIVERSITY OF FLORIDA
I am grateful to my advisor, Professor F. Wayne King, for his support and
guidance throughout my master's education at the University of Florida. Without his
help, I could not have accomplished the achievements I have made.
I am greatly indebted to Dr. James Perran Ross for his extensive advice and
unselfish help. I have greatly benefited by his stimulating approach to research and his
relentless pursuit of perfection. Many thanks are extended to him for his invaluable help
in preparation of this document. I thank also Professor Ray Carthy for serving on my
committee and for reviewing this thesis. Special thanks go to Dr. Franklin H. Percival for
his advice and help in improving my research and with logistics.
I must thank Allan R. Woodward for technical support and countless discussions
without which I could not have completed this work. He made significant contributions
to the fieldwork. I am overwhelmed with his tireless effort to improve the quality of the
work. I also appreciate much help from Florida Fish and Wildlife Conservation
Commission (FWC) biologists, Dwayne Carbonneau, Arnold Brunell, John White, Chris
Vischer, and Paul Kubilis.
To my friends and colleagues, Stanley Howater, Michael Cherkiss, Gregg
Klowden who have made my stay at Gainesville one of the most memorable periods of
my life, I offer my appreciation for the innumerable enjoyable discussions as well as for
the encouragement and support I received from them.
Special thanks go to my wife, Theeranan Temsiripong, for the happiness we
shared and for being with me to get through the hardship together. I am forever indebted
to my parents and my brothers. Without their endless love and sacrifice, I could not have
accomplished so much.
TABLE OF CONTENTS
L IST O F T A B L E S ....................................................... ........... ........... vii
LIST OF FIGURES ................................................................ ........... viii
A B STR A C T ............................................................................ ........ x
INTRODUCTION ............................................................................. 1
REVIEW OF LITERATURE..................................................... ......... 4
ST U D Y A R E A S .................................................................................... 7
Lake Apopka .......................................................................... 7
L ake G riffi n ................................................................... ...... . ..... 8
Orange Lake ............................................................................... 9
MATERIALS AND METHODS......................................... ................ 13
Egg Collection .............................................................. ......... 13
Egg Incubation .............................................................. ......... 14
Tagging and Releasing ......................................... ....................... 16
Post-Hatching Observation ................................................ ......... 17
Recapture ............................................................................. 18
G IS-T technology .................................................. ........... ......... 19
Data Analysis ......................................................................... 19
G row th R ate ........................................................ ......... 19
Survival Rate ....................................................... ......... 23
Statistical Methods ................................................................... 23
R E S U L T S ...................................................................................... ..... 2 5
Post-Hatching Observation....... ..................... ........... .... .......... 25
G row th R ate ............................................. . .......... ... ......... 29
Change in Total Length (TL)........................................... 30
Change in Snout-Vent Length (SVL)................................... 35
Change in Weight (W) ........................................................ 35
Body Condition Factor (K) ........................ ............................ 35
Survival Rate ......................................................................... 37
DISCUSSION ................................................................................. 42
Growth Rate .......................................................................... 42
Survival R ate ...................................................... ........... . . .... 44
CONCLUSION ....................................................................... ......... 47
R E F E R E N C E S .......................... ..................................... ....................... 4 9
BIOGRAPHICAL SKETCH ...................................... ............. 55
LIST OF TABLES
1. Results of egg collection and incubation of American alligators
from different locales in central Florida in 1998................................ 15
2. Sample sizes (number of pods) for each treatment and lake.......................... 16
3. Average water temperature in Lake Apopka, Lake Griffin,
and Orange Lake during the study period ............................ .......... 21
4. Movement summary during recapture of hatchling American alligators
in central Florida lakes ................................... ............. .......... 27
5. Behavioral summary of adult alligators observed at pod sites....................... 28
6. Recapture rates (by individual) of hatchling American alligators in
three central Florida lakes ........................................................... 29
7. Summary of ten-month growth increment in total length (TL) change and
Change of TL per day................................... ........................ ... 31
8. Regression equations and standard error of the regression for predicting
weight (W) from total length (TL) across three central Florida lakes ....... 36
9. Survival rates of hatchling American alligators in central Florida lakes ............. 38
10. Proportion of pods from which at least 1 hatchling alligator was
recaptured during a 9-month period on three central Florida lakes........... 38
LIST OF FIGURES
1. Satellite imagery of Lake Apopka, Florida
with alligator pod number and location ............................... ......... 10
2. Satellite imagery of Lake Griffin, Florida
with alligator pod number and location .................................. 11
3. Satellite imagery of Orange Lake, Florida
with alligator pod number and location .............................. .......... 12
4. Water temperature of lakes in central Florida during study period.
The minimum temperature for growth is 200C (Deitz 1979).
The four arrow lines depict the period of no growth days.
The three double arrow lines mean the period when no
growth occurred for the three lakes...................... ... ........ .......... 22
5. 95% Confidence Interval of total length (TL) change per growth day
of wild and repatriated hatchling American alligators in central
Florida lakes ............................................................ .......... 32
6. Differences in the variability of growth of hatchling American
alligators among different lakes and different treatments. 95%
Confidence Interval of total length (TL) change per growth day
in central F lorida lakes............................................................... 33
7. Relationship between hatching size and growth rate of hatchling alligators
(P = 0.213) in central Florida lakes................................... ............ 34
8. 95% Mean 9-month survival rate and confidence interval for wild and
repatriated hatchling American alligators in central Florida lakes.
Survival rate of wild hatchlings was greater (P = 0.028) than repatriated
hatchlings .................................................. ............... .......... 39
9. 95% Mean 9-month survival rate and confidence interval for wild and
repatriated hatchling American alligators in central Florida lakes.
Survivorship of was not different (P = 0.589) across the lakes................ 40
10. Relationship of survival rates of hatchling American alligators to clutch size
(P = 0.113) in central Florida lakes......................... .............. .. 41
Abstract of Thesis Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Master of Science
GROWTH AND SURVIVAL RATES OF WILD AND REPATRIATED HATCHLING
AMERICAN ALLIGATORS (Alligator mississippiensis) IN CENTRAL FLORIDA
Chairman: F. Wayne King
Major Department: Wildlife Ecology and Conservation
Egg harvests are implemented extensively by the Florida Fish and Wildlife
Conservation Commission (FWC) for American alligators (Alligator mississippiensis).
However, egg collection may influence population dynamics of alligators resulting in
changes of growth and survival rates. Egg collection and incubation was conducted on
Lake Apopka, Lake Griffin, and Orange Lake in summer, 1998. After hatching, 1,676
hatchlings were individually measured, weighed, marked, and released back at nest sites
and in suitable habitats away from nests. Growth and survival rates of 10 month-old
hatchlings were analyzed to investigate if there was a difference between wild and
repatriated hatchling alligators. Growth increment of animals from different localities
varied considerably among Lake Apopka, Lake Griffin, and Orange Lake (P < 0.01).
Survival of tagged wild alligators (29.3%) was 41% greater than that of repatriated
alligators (20.7%) (P = 0.028). Although the survival rate of repatriated hatchling
alligators was apparently less than that of wild alligators that were naturally hatched, this
added mortality may have compensated for by increased survival of collected eggs by
protecting them from flooding and depredation. Therefore, the net effect of egg
collections with repatriation on the population dynamics of these alligator populations
would be negligible.
The American alligator (Alligator mississippiensis) exists in a wide range of
aquatic habitats throughout the southeastern United States from North Carolina to Florida
and west into Texas. In the wild, American alligator eggs are subject to flooding (Hines
et al. 1968, Fogarty 1974, Jennings et al. 1988), depredation (Goodwin and Marion 1978,
Deitz and Hines 1980), desiccation (Ferguson 1985), and disturbances by nesting turtles
(Goodwin and Marion 1977, Deitz and Jackson 1979). It is a common practice around
the world to remove crocodilian eggs and hatchlings from the wild for commercial use
and restocking of endangered species. In Florida, a proportion of alligator eggs is
collected and incubated in captivity for research purposes and the hatchlings released. A
key question is whether this practice affects growth and survival rates of repatriated
Growth rates and changes in growth with age and size are important life-history
characteristics. Growth rates of numerous reptiles including alligators are known to vary
geographically as well as by habitat and individual (Andrews 1982). It is evident that
different pods (groups of siblings) have different growth and survival rates, which could
be due to many factors.
The logarithmic relationship between total length or snout-vent length and body
mass is used to evaluate condition factors (Taylor 1979). Condition factors are an index
of animal's health (Le Cren 1951). The factors have been used to make seasonal and
habitat comparisons (Taylor 1979, Elsey et al. 1992).
Alligators are most susceptible to mortality, through natural causes and from
predators, while embryonic in the nest or during the first few years of life. While in the
nest, eggs are subject to fluctuations of environmental parameters and direct predation of
egg-eating animals taking a heavy toll of unguarded clutches, both by day and night
(Woodward et al. 1989).
Most of the generalities about crocodilians can be applied to alligators. Many
species occupy densely vegetated or remote areas. They are behaviorally very
sophisticated reptiles. An early work has demonstrated that crocodilians possess well-
developed sensory abilities (Bellairs 1971), display repertoires and social systems
(Modha 1967, Garrick and Lang 1977, Garrick et al, 1978), learning abilities (Northcutt
and Heath 1971) and reproductive behaviors which include extensive parental care (Hunt
1975, Pooley 1977). McIlhenny (1935) described parental behaviors of alligators
previously unreported for any crocodilian or, in fact, any reptile. Alligator nest guarding
and nest opening behaviors were discussed, and Kushlan (1973) first described maternal
duties from moving her fresh hatchlings to defending of groups of sibling (pods). Carr
(1976) pointed out that most of McIlhenny's and Kushlan's observations were supported
by subsequent investigations. Deitz (1979) was the first to provide quantitative data of
these complex behaviors by finding that maternal presence, which involves regular
maternal attendance or defense, was observed for 34% of all pods in central Florida lakes.
This leads to the question of whether growth and survival of naturally hatched pods is
different from that of repatriated pods. Adult alligators, presumably maternal females,
were observed readopting the pods released at the nest site (Woodward, pers. comm.).
Understanding the reasons of early age mortality will aid in the management and
conservation of the species.
The objective of this study is, first, to determine if growth and survival of
hatchling American alligators is different between wild and repatriated hatchlings across
several locales in central Florida. Second, to find out whether hatchlings released at the
nest site have a greater chance of survival and faster growth rate than those released at
suitable habitat away from the nest site. This was accomplished by comparing relative
growth rate, body condition factor, and survival rate between wild and repatriated pods.
REVIEW OF LITERATURE
Although only some alligators actively defend their nests against humans (Reese
1915, Joanen 1969, Cott 1971, Metzen 1978, Deitz 1979, Kushlan and Kushlan 1980,
Hunt and Watanabe 1982), most if not all, tend their nests through the incubation period
(Joanen 1969, Joanen and McNease 1970, Hunt and Watanabe 1982). Far from
terminating maternal behavior, the post-hatching period seems to be a continuation of the
complex relationship between mother and offspring. In 1976, Watanabe (1980) observed
and photographed a female scraping her nest open with her forefeet and carrying some of
the hatchlings to water in her mouth. Kushlan (1973) reported a mother carrying one of
her vocalizing hatchlings from a roadbed where he had taken it. The amount and
duration of parental care that pods receive is extremely variable in nature. Deitz (1979)
pointed out that most protective females care for their pods from hatching to at least the
onset of cold weather. Further some females remained in close association with their
pods through the following spring. Woodward et al. (1987) reported that hatchlings
remained together in pods for at least their 1st year and then began to disperse during their
2nd spring and summer.
Early conservation interest in the alligator beginning in the 1960's has led to
many quantitative studies on growth (Hines et al. 1968, Chabreck and Joanen 1979,
Brandt 1991, Magnusson 1995, Dalrymple 1996). Males grow faster than females in
Crocodylus niloticus (Graham 1968) and A. mississippiensis (McIlhenny 1935, Deitz
1979). Differences in growth rates of Louisiana and Florida alligators are probably not
significant until juveniles reach at least 60 cm SVL (Nichols et al. 1976). Deitz (1979)
studied the mean yearly growth increment in north Florida (11.9-21.1 cm/yr), which is
about the same as in Louisiana (22.0 cm/yr) reported by Chabreck and Joanen (1979). It
was higher than that reported by Fuller (1981) in North Carolina (12.4 cm/yr) and
Dalrymple (1996) in south Florida (13.6 cm/yr). However, most studies, based growth
rates on small sample size, included animals of unknown age and of various size classes,
and relied mainly on recaptures over short time intervals. These studies have shown
great variability in growth rates and age at maturity of alligators from different
geographic areas, and habitats, and among different ages, sizes, and sexes. Not all
methods of age estimation are equally reliable for crocodilians (Magnusson and Sanaiotti
1995). Size frequency analyses are difficult to interpret because of large individual
variation and the possibility that reproductive failure may mean that some year classes
are missing. Because of this variability, population models (and harvest schedules based
on these models) based on data from one area may not be applicable to other areas
(Brandt 1991). Therefore, more detailed information on the extent and pattern of
variability in growth rates within and among populations is needed.
Recent studies have indicated wide variation in survival rates of alligators. For
example, Nichols et al. (1976) estimated that the average annual survival rate was 78.8%
for alligators in the 1.2-1.5-m TL size class in southwestern Louisiana based on size class
distribution. Taylor and Neal (1984) used a size class frequency distribution and found
that 59.2% of alligators of the 1.2-m TL size class survive to the 1.5-m TL size class.
Deitz (1979) found that 30% of a sample of lake alligators survived through their first
year in Florida. Woodward et al. (1987) estimated 1-year survival of hatchling alligators
in Orange Lake, Florida to be 41%. The wide range of estimates of survival rates is
attributable in part to the differences between years and areas and also reflects biases due
to different techniques (Chabreck et al. 1998).
Mortality explained earlier may be due to behavioral disturbances. Recently,
Huchzermeyer (1997) found in captive breeding situations that C. niloticus hatchlings
housed with a "substitute mother" made out of concrete slab or pipe had a lower level of
stress. He proposed that stressed hatchlings had high plasma corticosterone levels, which
lead to behavioral disturbances and appeared to be responsible for a large proportion of
mortality in intensively reared crocodile hatchlings. Consequently, high levels of plasma
corticosterone can cause slower growth rate. Elsey et al. (1990) found change in body
weight was negatively correlated with plasma corticosterone; the lower the hormone
levels, the faster the rate of growth.
Marking techniques have been used widely in fishery and wildlife management to
obtain information on migration, behavior, population size, and stocking success (Emery
and Wydoski 1987). Five marking techniques used for many of crocodilian studies were
tagging, web-hole punching, toe-clipping, freeze branding, and scute-clipping. Jennings
et al. (1991) had proved that these marking techniques have no effect on growth or
survivorship of hatchling alligators. Even though scute-clipping appeared to be one of
the best marking techniques, tagging was appropriate for this short-term study and also
easy to apply in the field.
Lake Apopka is the head water lake for the Ocklawaha Chain of Lakes (Figure 1).
The lake is located in Orange and Lake counties, Florida, at Latitude 28' 37' N and
Longitude 810 38' W. The water surface of the lake is approximately 12,465 ha (Conrow
et al., 1993), average depth is 1.65 m, average Trophic State Index (TSI) has varied from
82-91 (hypereutrophic condition), and the lake is considered the most severely polluted
large Florida lake (U.S. EPA 1979). The lake water is well buffered, alkaline, highly
turbid, and pea-green in color (Secchi transparency about 30 cm (12 in) or less).
Consequently, the water quality of Lake Apopka is very poor. The biota of the
community reflects its hypereutrophic chemical status. Blue-green algae dominate the
water column throughout the year. The limited amount of emergent vegetation is
predominantly cattails (Typha sp.), with some stands of bullrush (Scirpus sp.), and
knotgrass, (Paspalidium geminatum) interspersed around the lake shoreline.
Alligator population sizes were estimated from annual night-light counts during
1995-1999 and adjusted for observability (Murphy 1977) by the Florida Fish and Wildlife
Conservation Commission (FWC). Alligator surveys indicated that Lake Apopka
alligator population density is 77.2 alligators/shoreline mile for juvenile less than 4 feet,
and 20 alligators/shoreline mile for 4-foot and larger alligators. Juvenile population trend
was increasing (B = 0.265, P = 0.01), but 4" and larger alligators had a stable population
trend (B = -0.057, P = 0.16).
Lake Griffin is a large (6,679 ha) mesotrophic lake, with extensive marshy areas
adjacent to northern portion of the lake and Oklawaha river (Florida LAKEWATCH
1996). The lake is located in Lake county, Florida at Latitude 280 51' 33" N and
Longitude 810 50' 52" W (Figure 2). Trophic State Index (TSI) has varied from 80-90
(Walt Godwin, DWMP, pers. comm.). The lake is dominated by deeply weathered
clayey sand and granular sand of the Hawthorne Formation (Florida LAKEWATCH
1996). The lake water is well buffered, alkaline, highly turbid, and pea-green in color
(average Secchi transparency about 57.9 cm (Florida LAKEWATCH 1996)). Recent
algal bloom affected the lakes in many ways, for example, there are more particles
intercepting sunlight and heating up the water resulting in the warmer water temperature
above average (Ross, pers. comm.). The temperature, then, dropped slower than that of
Lake Apopka and Orange Lake during the onset of winter.
Alligator surveys by FWC in 1995-1999 indicated that Lake Griffin supports an
alligator population comparable to Lake Apopka in density (76.1 3" and smaller
alligators/shoreline mile and 50.2 4" and larger alligators/shoreline mile). Population
trend for 3" and smaller alligators was stable (B = 0.135, P = 0.29), but it is increasing in
4" and larger alligators (B = 0.187, P = 0.01).
Orange Lake is a large (5,330 ha) mesotrophic lake, with extensive marsh
covering portions of the basin (Brezonik and Shannon, 1971). The lake is located in
Alachua county, Florida, at Latitude 290 27' 20" N and Longitude 820 10' 20" W (Figure
3). Trophic State Index (TSI) is 59.6 and exhibits no significant long-term trend in water
quality (Walt Godwin, DWMP unpublished data). Characteristic of marsh areas of this
lake is a heavy buildup of peat. Gasses formed by decomposition bring large chunks of
peat to the surface, resulting in floating islands and floating mats extending out from the
lakeshore. Vegetational composition of these islands and fringe areas is largely
Sagittaria lancifolia, Cladium jamaicensis, Hydrocotyle umbellata, Panicum sp., Myrica
cerifera, Cephalanthus occidentalis and Decodon verticillatus. Nupha lutem and Typha
sp. covers extensive portions of the open water margins, with Eichornia crassipes,
Limnobium spongia and Pistia stratiotes common in more sheltered areas. In some areas,
there is abundant submerged growth of Hydrilla verticillata, which is a suitable habitat
for young American alligators.
FWC conducted alligator surveys in 1995-1999 indicating that Orange Lake
alligator population density was 63.8 alligators/shoreline mile for juvenile less than 4
feet, and 52 alligators/shoreline mile for 4-foot and larger alligators. Both juvenile (B =
0.361, P = 0.03) and 4"and larger (B = 0.174, P = 0.01) alligator population trend was
Figure 2. Satellite imagery of Lake Griffin, Florida with alligator pod number and
MATERIALS AND METHODS
Alligator eggs were collected as part of an ongoing Florida Fish and Wildlife
Conservation Commission (FWC) clutch viability investigation from perimeter marshes
and swamps on Lake Apopka, Lake Griffin, and Orange Lake in central Florida (Figures
1, 2, and 3). Entire clutches from a sample of accessible nests in each collection area
were collected. Eggs were collected from 23 June to 6 July, 1998. A helicopter was used
to locate nests and to direct airboat crews to nests by air-to-ground communications.
Before removal, eggs were uncovered and marked on their upper axis, next to the opaque
band (Ferguson 1985), with a waterproof-marking pen. Eggs were transferred to a
50x35xl3-cm plastic pan lined with 5-7 cm of nest material. We were careful not to
invert, rotate, or otherwise agitate eggs. If two layers of eggs were placed in a pan, a 1-
cm-thick layer of nest material was used to separate layers.
A second layer of nest material was placed over the eggs to provide insulation and
protection during transportation. Pans packed in this manner were hand-held and
transported individually in a small airboat (3.6 m long) to a larger airboat (4.5 m),
minimizing excessive motion and shocks from waves and uneven terrain. Inflated tire
inner tubes were placed on the floor of the larger boat and covered with alternating sheets
of 1.6-cm-thick plywood and 5-cm-thick foam rubber to separate and cushion layers of
pans during transport. We used similar packing methods when transporting clutches by
pick-up truck to incubators. Temperatures were monitored to ensure that the eggs were
maintained between 280C and 330C from the time of collection until reaching the
incubator at Wildlife Research Laboratory, Florida Fish and Wildlife Conservation
After the eggs were removed, we noted moisture content (dry, moist, or saturated)
of the nesting material, presence and level of water in the egg cavity, evidence of
previous flooding, % shade, measurement of the mound, and evidence of attendant
alligators. Global Positioning System (GPS) coordinates were taken at the nest sites to
assist navigation when returning back to release hatchlings. Coordinates of important
map points such as boat ramp and waypoints were also recorded. We collected twenty-
five clutches from Lake Apopka, thirty clutches from Lake Griffin, and forty-one
clutches from Orange Lake (Table 1).
Alligator eggs were artificially incubated as described by Woodward et al. (1989)
to examine inherent egg viability. A 1-room incubator was maintained at constant
temperature (mean = 32.10C, range 30.20C-34.40C) and humidity (mean = 92%, range
85%-94%). Egg fertility was determined by the presence of an opaque spot or band
(Ferguson 1981, 1985; Webb et al. 1987). Embryo viability was determined by
comparing the consistency of opaque bands among eggs in a clutch, egg odor, general
color of eggs, and color of egg contents when transilluminated (Ferguson 1982). We
removed all infertile eggs and eggs with dead embryos before incubation. A total of
eighty-two clutches hatched from this artificial incubator (Table 1).
Table 1. Results of egg collection and incubation of American alligators from different
locales in central Florida in 1998.
No. of clutch No. of egg Viability Hatch No. of clutches
Lake collected collected Rate1 Rate2 successfully hatching
Apopka 25 1,171 0.47 0.67 25
Griffin 30 1,457 0.29 0.54 16
Orange 41 1,448 0.63 0.85 41
Source: The Florida Fish and Wildlife Conservation Commission (FWC)
1 Viability rate was the proportion of eggs successfully hatching from a total clutch of
eggs (Woodward et al. 1993).
2 Hatch rate of incubated eggs.
Tagging and Releasing
Each hatchling was tagged on the web of right-rear foot. The tag is in numerical
series for each clutch so that it is convenient to recognize and verify in the field. Number
1 monel tags (Natl. Band and Tag Co., Newport, Ky.) were used to identify individual.
All pods were measured TL (total length) and SVL (snout-vent length), weighed, tagged,
and relocated into the wild following treatments described below. TL and SVL were
measured to the nearest 0.1cm. Hatchlings remained in captivity for approximately 2
weeks before releasing due to the large number of clutches needed to be released. Only
pods with at least 8 hatchlings were selected as experimental units. Therefore, the
number of pods used in this study (Table 2) was smaller than the number of clutches
produced in 1998 (Table 1)
Table 2. Sample sizes (number of pods) of hatchling alligators monitored for each lake
Treatment Apopka Griffin Orange Total
Repatriated at nest site 10 6 9 25
Repatriated at suitable habitat 7 5 19 31
Wild 8 8 6 22
Total 25 19 34 78
Repatriated pods were released at known nest sites and in suitable habitat away
from the nest site (Table 2). The word "Nest Site" defines the same site as egg collection
site, while the word "Suitable Habitat" means an area that appeared to be suitable for
hatchling alligators (Deitz 1979, Woodward et al. 1987) but separated from the nest site.
Hatchlings released at nest sites were assumed to have associated maternal female
alligators, whereas, hatchlings released in suitable habitats, were assumed to not be
associated with maternal females. With this treatment design, differences in growth and
survival could be influenced by the differences in treatments.
In addition, naturally hatched wild hatchlings were located and captured at night,
measured TL and SVL, weighed, and tagged in the same fashion as repatriated
hatchlings. Wild hatchling alligators were caught for tagging from airboats after locating
eyeshines with a 200,000 c.p. spotlights and 15,000 c.p. head lamps. Alligators were
caught by hand or by Pillstrom Tong (Pillstrom Tong Co., Ft. Smith, Ark.). The GPS
position was also taken for later relocation. Locations of capture and recapture sites were
ground-marked with bright colored flags and reflective nails for night detection.
Hatchlings (groups of siblings) from one clutch are commonly referred as a
"pod." I conducted periodic observations of pods after releasing them to monitor pod
movements. Each month during the study period, every pod was visited at least twice,
once at night to capture one marked hatchling to verify pod identity and once during the
daytime to observe the distance traveled and whether an adult alligator was present.
Attempts to follow marked hatchlings were made every three months in October,
January, and April to make sure they did not disperse a great distance. The last recapture
was in May-July 1999 except for 3 Apopka pods that were checked in September 1999. I
went back to the pod sites by following the coordinates from a GPS unit along with the
satellite imageries and attribute data (pod location) on it (Figures 1, 2, and 3) and
captured as many individuals as possible. Marked sites were revisited at night to capture
marked hatchlings by searching the immediate area around the nest with a low intensity
(15,000 c.p.) spotlight. If hatchlings could not be found, the search pattern was expanded
for up to 200 m to cover accessible marsh and open water in the general vicinity of the
nest. All pods were recaptured with the best and equal effort. Weather was one of the
most important factors affecting hatchling capture. If wind and waves were too strong,
hatchlings would climb up on land to avoid disturbances. Therefore, if the wind was too
strong, it was extremely difficult to capture hatchlings. In such cases I returned and
recaptured them again on a calm night. The number of nights I spent to recapture
hatchlings varied across lakes. I spent 6, 5, and 9 nights in Lake Apopka, Lake Griffin,
and Orange Lake respectively.
Hatchlings were captured by hand or with Pillstrom tongs. All animals were
weighed, measured TL and SVL for analyses of growth rate and body condition.
Individual data on capture-history used in the analysis, and estimates of the TL of
attending alligators were also estimated if applicable. In addition, environmental
conditions such as air and water temperature, water level, wind speed, and general habitat
were noted. Recapture and data collection for each pod was accomplished as fast as
possible to reduce stress and then all animals were released at the site of capture. Sex
was identified by cloacal examination. Sexes were determined by comparing clitero-
penis color and dimensions (Allsteadt and Lang 1995).
The general approach combines the use of digitized topographic map layers of
attributes (such as waterways, roads, vegetation type) and images (aerial photographs,
satellite imagery, or digitized maps) supported by Florida Department of Environmental
Protection (DEP). Application of geographic information system (GIS) technology to
this project has had many additional benefits over more conventional mapping. The
position of hatchling alligators and nest site were recorded via a GPS (Global Positioning
System) in degrees and minutes of latitude and longitude which were then converted to
decimal degrees for use in an Arcview 3.1 program (Figures 1, 2, and 3).
Growth rate was calculated as a total length (TL) change per growth day
(cm/day). I used TL rather than SVL because there is greater standardization among
researchers in the measurement of TL (Addison Jr. 1993 and Moler 1992). Growth days
were referred to Deitz's thesis (1979) as the period prior to and after the cooler months
when no growth occur. During no-growth period the water temperature dropped below
200C (Coulson and Hernandez 1983). The length of this period is different across the
lakes. Orange Lake had the shortest estimated growth period (365-120 = 245 days),
whereas it was 265 and 285 days in Lake Apopka and Lake Griffin respectively (Table 3
and Figure 4). Log transformation was used to transform TL, SVL, and W to make them
normally distributed. The total length change, then, was calculated by this equation.
Growth days from capture1 to capture2
Growth increment was also calculated using SVL to avoid problems resulting
from tail tip loss. In order to find out the best index
Growth days from capture, to capture2
Change in weight was calculated in a similar fashion to obtain the best indication
of growth rate. This was a relative weight gain since it was compared to each other.
Weight 2 Weight 1
Growth days from capture, to capture2
Condition factors (Le Cren 1951) are an index of the robustness of an animal and
can be an indicator of well-being (Taylor 1979). Condition factors are derived from the
relationship between length and weight in the population, K = W x L-b. K is a condition
factor, W is mass (g), L can be either snout-vent length or total length (cm), and b is the
slope of the regression of the natural log (In) of TL on the natural log of mass. The
constant "b" is dependent upon mean growth characteristics of individuals in the
population and equals the slope of regression equation where InTL is plotted against InW.
An individual relative condition factor (ai) is then calculated as ai = WI(LI)-b (Taylor
Table 3. Average water temperature in Lake Apopka, Lake Griffin, and Orange Lake
during the study period.
Month Lake Apopka (C) Lake Griffin (C) Orange Lake (C)
7/98 29.7 30.6 28.5
8/98 30.2 29.0 30.0
9/98 26.0 28.4 26.7
10/98 25.6 26.3 26.2
11/98 23.7 24.2 23.3
12/98 20.1 21.9 18.0
1/99 19.0 19.3 17.0
2/99 14.3 18.6 17.5
3/99 19.1 17.7 18.5
4/99 24.0 26.7 22.7
5/99 25.5 23.1 23.9
6/99 27.9 27.5 27.3
Average 23.6 24.5 23.1
SD 4.9 4.3 4.7
Source: Department of Water Resources, SJRWMD
18 :'..""...1!/. LAKE
o 16 .Apopka
14 ......................... Griffin
Monthly 22period (09/98 06/99)
Figure 4. Water temperature of lakes in central Florida during study period. The
minimum temperature for ....growth LAKE
14 i.. ,Griffin
Monthly period (09/98 06/99)
Figure 4. Water temperature of lakes in central Florida during study period. The
minimum temperature for growth is 20C (Deitz 1979). The four arrow
lines depict the period of no growth days. The three double arrow lines
indicate the period when no growth occurred for the three lakes.
Survival rate was calculated by using Minimum-Known-Alive (MKA), which has
been used extensively by crocodilian researchers because of its simplicity and for single
recaptures. MKA survival rates represent the proportion of marked hatchlings known to
survive to a certain age from an initial sample of marked animals. Even though MKA
estimates are negatively biassed (Nichols and Pollock 1983), it is still qualified for this
study because I was concerned more with relative rather than absolute survivorship of
All analyses of growth and survival rate were done by computer using SPSS
versions 7.5 and 9.0 for Windows (Norusis 1991, Voelkl and Gerber 1999). My
statistical design was a factorial analysis of variance to test effects of factors influencing
growth and survival. It allowed for 2-way interactions between the effects of treatment
and study areas on each response variable. This design was intended to test the following
null-hypotheses. First, there was no difference in growth rate and survivorship among
study areas. Second, there was no interaction among treatment and study area effects on
growth and survival rates. Third, there was no difference in growth and survival rates
between repatriated hatchlings at nest site and in suitable habitats. Finally, there is no
difference in growth and survival between wild and repatriated hatchlings. The last
hypothesis would be tested if there is no difference in growth and survival rates between
repatriated hatchlings at nest site and in suitable habitat. If my hypotheses are valid, I
should find differences in growth and survival rates between repatriated and wild pods in
different locales in central Florida. Assumptions that have to be made are the following.
First of all, pods are independent. Second, measurements are taken from normally
distributed populations, which will be tested by Kolmorogov-Smirnoff Test. Last, the
populations of growth and survival rates have equal variances tested by Levene's Test.
Egg collection was conducted on Lake Apopka, Lake Griffin, and Orange Lake in
June and July 1998. After hatching, 1,676 hatchlings were marked and released.
Repatriated hatchlings were released in September 1998, and recaptured in May-July
1999. Growth and survival data of hatchling alligators were collected from the marked-
Post-Hatching observation was implemented to reveal where the pod would be
after releasing. A total of 64 hours of daytime-observation was accomplished. Pod
locations in Lake Apopka, Lake Griffin, and Orange Lake were digitally plotted in
satellite images (Figures 1, 2, and 3 respectively). I found that hatchling American
alligators moved little throughout the winter and were mostly inactive except on warm,
sunny days. There was some tendency for pods to be extremely closely aggregated
during cold weather. For example, on the cold night (160C) of 5 December 1998,
eighteen hatchlings were observed with more than ten 1-2 year old alligators near
McCormick Island, Orange Lake. They stayed afloat very close to each other (less than
0.1 m). They were sluggish at this temperature, but were capable of coordinated
movements and vocalized readily when captured. After hatching, American alligators
formed pods and remained among aquatic vegetation. Hatchlings frequently vocalized
while concealed in vegetation. From diurnal observation, adult alligators were
occasionally observed near pods, but made no attempt to defend them, and I did not
observe them responding to hatchling distress calls. Hatchlings were often observed
foraging in non-vegetated shallows and occasionally lying on logs in open water.
Movement of hatchlings following their first winter was documented by monthly
recaptures of one hatchling from each pod. Pods remained at nests for at least ten
months. Most pods (77%) stayed at the original site even after the first winter. There
were 3 Lake Apopka pods, 3 Lake Griffin pods, and 6 Orange Lake pods scattering along
the shorelines, representing 15% of all tagged hatchling pods (Table 4). Average
distance travel of these 12 pods from the three lakes was 83.5 m. Dispersed pods usually
display a one-dimensional spreading along the lake or marsh fringe. Six repatriated pods
(1 Lake Griffin and 5 Orange Lake pods) or 8% were not found (Table 4).
Sixty-four hours diurnal observation was not sufficient to draw a detailed
conclusion on parental behavior. However, recapture at night gave additional
opportunities to observe them. The size of all adult alligators observed near hatchlings
fell in the range of adult female alligators. Seventy percent of female-sized alligators
observed near nursery pond were very persistent (Table 5). Even though they submerged
as the airboat approached, they resurfaced to observe us working up hatchlings. In
presence of the female, non-distress grunting of hatchlings occurred in continuous and
apparently random fashion. Hatchlings grunted frequently when searching for food or
exploring their environment. Such behaviors happened more often in the presence of the
female and this agrees with the findings of Deitz (1979).
Table 4. Movement summary during recapture of hatchling American alligators in
central Florida lakes.
W = Wild hatchlings
N = Repatriated hatchlings at the nest site
S = Repatriated hatchlings into suitable habitat away from the nest site
Table 5. Behavioral summary of adult alligators observed at the pod sites.
Pod No. Locale Time Adult alligator behavior
AP-20N Apopka 0015 7'-8' alligator at location, fled upon approach
GR-402W Griffin 2210 7.5' alligator stayed afloat all the time we were present
GR-10N Griffin 0009 7' alligator observed our activities 15 m away from
OR-506W Orange 2320 7'-8' alligator submerged as we approached, kept 10 m
OR-45N Orange 2345 7' alligator submerged immediately as we approached
OR-126N Orange 2125 7' alligator submerged shortly after we shined light on
OR-4S Orange 0015 7.5' alligator submerged as we approached, resurfaced
briefly as we were working
OR-25S Orange 2205 7'-8' alligator observed our activities, responded to
OR-27S Orange 0015 7.5' alligator submerged as we approached, resurfaced
briefly as we were working
OR-117S Orange 2250 7.5' alligator in midst of pod, submerged promptly and
resurfaced during work up
W = Wild hatchlings
N = Repatriated hatchlings at the nest site
S = Repatriated hatchlings into suitable habitat away from the nest site
Of 1,676 wild and repatriated hatchling alligators from 78 clutches marked and
released during the study, 372 (214 females, 157 males) or 22.2% were recaptured and
used for growth analysis (Table 6). Mean hatchling alligator measurements of repatriated
animals (n = 1,527) are as follows: SVL = 13.0 0.5 cm (range = 10.3 to 14.1 cm); TL =
26.5 1.0 cm (range = 20.5 to 29 cm); mass = 51.3 5.3 g (range = 28.9 to 76.4 g).
Mean hatchling alligator measurements of wild animals (n = 149) are as follows: SVL =
13.9 1.3 cm (range = 10.5 to 16.6 cm); TL = 28.2 2.6 cm (range = 20.5 to 33.5 cm);
mass = 62.29 10.9 g (range = 30 to 90 g).
Table 6. Recapture rates of hatchling American alligators on three central Florida lakes.
Lake No. capture, tag and release No. of recapture Recapture rate
Apopka 525 119 0.23
Griffin 429 80 0.19
Orange 722 173 0.24
Overall 1,676 372 0.22
Change in total length (TL)
The sex ratio for 371 hatchlings was 1:1.36 (males:females). The difference in
length gain was not detected (P = 0.916) between male (n = 157) and female hatchlings
(n = 214). There was no correlation (Figure 7) between initial size of hatchlings and
change in TL per day (P = 0.213). Similarly, growth rate was not correlated with clutch
size (P = 0.417). Change in length did not correlate with the rate of survival (P = 0.054,
R = 0.052). No difference was detected between hatchlings released at nest site and in
suitable habitat (P = 0.226). The difference in TL change/day between wild and
repatriated hatchlings (Figure 5) was not significant (P = 0.580). However, growth rate
differed among Lake Apopka, Lake Griffin, and Orange Lake (P < 0.01). There was no
interaction among LAKE x TREATMENT effects (P = 0.063) on growth rate (Figure 6).
Table 7. Summary of ten-month growth increment in TL change and Change of TL per day for alligator hatchlings on central Florida
lakes during 1998-1999.
Lake recapture date No. of pod
TL (cm)1 TL (cm/day)2
Released at Nest site Released in Suitable habitat
TL (cm)1 TL (cm/day)2 TL (cm)1 TL (cm/day)2
** (P < 0.01)
1 Average 10 month increase in total length (TL)
2 Average 10 month increase in total length change per growth day
Figure 5. 95% Confidence Interval of total length (TL) change per growth
day of wild and repatriated hatchling American alligators in central
Florida lakes. The difference in TL change/day between wild and
repatriated hatchlings is not significant (P = 0.580).
at the nest site
in the suitable habitat
Figure 6. Differences in the variability of growth of hatchling American alligators
among different lakes and different treatments. 95% Confidence
Interval of total length (TL) change per growth day in central Florida
lakes. There was no interaction among LAKE x TREATMENT effects
(P = 0.063) on growth rate.
.18. y = 0.155-0.02x 3
-e R2= 0.007 0 
E.16- n = 220 0 Do
P = 0.213
.14 0 0 [3
m .12 0 3 3
13 *Eb 0 3 D3 D0 03
S.06 0 [ 0
20 22 24 26 28 30
Hatchling size (cm)
Figure 7. Relationship between hatching size and growth rate of hatchling
alligators in central Florida lakes.
Change in Snout-vent Length (SVL)
There was no difference in SVL change/day between hatchlings released at the
nest site and in suitable habitat away from the nest (P = 0.118). Therefore, SVL growth
rates of all repatriated hatchling were compared with wild hatchlings. There was no
difference in SVL change/day between wild and repatriated hatchlings (P = 0.536).
Conversely, SVL differed among lakes (P < 0.01). LAKE x TREATMENT interaction
(P = 0.128) was not detected indicating no difference in SVL change/day due to lakes and
Change in Weight (W)
There was no difference in weight gain between hatchlings released at the nest
site and at suitable habitat away from the nest (P = 0.207). The gain in weight per day
was not different between wild and repatriated hatchlings (P = 0.047). However, the
difference in weight gain was highly significant across Lake Apopka, Lake Griffin, and
Orange Lake (P < 0.01). LAKE x TREATMENT interaction (P = 0.024) was also
detected indicating a difference in weight change/day due to lakes and treatments
Body Condition Factor (K)
As hatchlings grew they showed a slight but significant reduction in mass relative
to length. When growth is isometric, the factor b will be equal to 3; therefore, the K
factor for all animals can be calculated for each individual based on the equation K = M x
10269/TLb (Table 8). The condition factor (K) showed that Orange Lake alligators have a
greater K (K = 2.78), meaning that alligators in Orange Lake have more mass relative to
length than those in Lake Apopka (K = 2.48) and Lake Griffin (K = 2.38).
Table 8. Regression equations and standard error of the regression for predicting weight
(W) from total length (TL) across three central Florida lakes.
Lake Predictor Estimated Value Equation R2 SE
Overall lnTL lnW Y = 2.6931nTL 4.843 0.92* 0.09
Apopka InTL InW Y = 2.4811nTL 4.077 0.86* 0.08
Griffin InTL InW Y = 2.3811nTL 3.630 0.79* 0.10
Orange InTL InW Y = 2.7781nTL 5.167 0.95* 0.09
(P < 0.0001)
Survival rate was determined by the number of marked hatchlings that survived
through the date of last recapture (Table 9). I recaptured at least 1 member of 92.3% of
pods tagged and released (Table 10). Although 72 out of 78 pods were found after 10-
month study periods, only 372 out of 1,676 hatchlings (22.2%) were actually recaptured
(Table 6). The six missing pods were all repatriated pods even though the best efforts
focused on every pod while recapturing. No difference in survivorship was detected (P =
0.546) between repatriated hatchlings released at nest site and in suitable habitat.
Likewise, survivorship was not different (P = 0.589) across the three lakes (Figure 9). No
LAKE x TREATMENT interaction (P = 0.722) was detected indicating that there was no
difference in survival rate among treatments across lakes. No relation was detected
between survival rate and clutch size (P = 0.113, R2 = 0.033, n = 78) (Figure 10).
Therefore, both repatriated treatments and all lake treatments were combined to test for
difference between survivorship of wild vs. repatriated hatchlings. The survivorship of
wild hatchlings pods (mean = 29.30, SD = 14.7, n = 22) was greater (P = 0.028) than
repatriated pods (mean = 20.74, SD = 15.60, n = 56).
Table 9. Survival Rate of hatchling American alligators in central Florida lakes.
* (P = 0.028)
Repatriated hatchlings released at
Nest site Suitable habitat
0.27 0.12 0.18 0.12
0.15 0.11 0.14 0.08
0.22 0.17 0.22 0.20
0.22 0.14 0.20 0.17
Table 10. Proportion of pods from which at least 1 hatchling alligator was recaptured
during a 9-month period on three central Florida lakes.
Capture and Tag (pod) Recapture (pod) Recapture rates
0 2 .
Wild Hatchling Repatriated Hatchling
Figure 8. 95% Mean 9-month survival rate and confidence interval for wild and
repatriated hatchling American alligators in central Florida lakes. Survival rate
of wild hatchlings was greater (P = 0.028) than repatriated hatchlings.
Apopka Griffin Orange
Figure 9. 95% Mean 9-month survival rate and confidence interval for wild and
repatriated hatchling American alligators in central Florida lakes.
Survivorship of was not different (P = 0.589) across the lakes.
0.6, y = 30.3948-0.3369x
0.5. n = 78
P = 0.113
0.4, D D
a 0 0 00 3
0 13 13 13 03 3
0.12 0 0
0 10 20 30 40 50
Figure 10. Relationship of survival rate of hatchling American alligators to clutch size
in central Florida lakes.
Repatriated hatchling alligators grew at rates similar to wild alligators but did not
survive as well. In general, no difference was found between growth rates and survival
rates of repatriated hatchlings released at nest sites or in suitable habitat. However
growth rates and survival rates differed among study areas. The difference was not
consistent and depended on treatment.
Growth rates were compared between wild and repatriated hatchlings across
different locales in north central Florida. The gain in TL and SVL was different among
lakes. The ten months growth increment of wild hatchlings was 24.03 cm which was
higher than repatriated hatchlings at the nest site (17.65 cm) and at suitable habitat away
from the nest (21.16 cm). Deitz (1979) studied the mean yearly growth increment in
north Florida (11.9-21.1 cm/yr) about the same as in Louisiana (22.0 cm/yr) reported by
Chabreck and Joanen (1979). However, it was higher than that reported by Fuller (1981)
in North Carolina (12.4 cm/yr) and Dalrymple (1996) in south Florida (13.6 cm/yr).
It can be seen that the average length gain of repatriated and wild hatchlings
differs across lakes. Growth in Orange Lake was significantly greater than the other
lakes (Table 7). Because body condition factors can be used to make habitat comparisons
(Taylor 1979, Elsey et al. 1992), the greatest body condition factor was found in
alligators from Orange lake indicating that Orange Lake hatchlings were heavier than
Lake Apopka and Lake Griffin animals at the same size. Perhaps, one of the most
important reasons for the difference is food availability because Orange Lake alligators
not only grew at the faster pace, but they were heavier as well. The effects of habitat on
growth rates of hatchling alligator were presumably related to food availability. Prey of
hatchling alligators consists largely of macroinvertebrates and fish (Fogarty and Albury
1967, Chabreck 1971). The abundance and availability of these items varies considerably
with water temperature, water depth and trophic state of the habitat. For example,
alligators in Everglades National Park have an extremely low growth rate (Kushlan and
Jacobsen 1990). Kushlan and Jacobsen suggested that the lower growth rate of
Everglades alligators was due to seasonal shortages of food combined with the prolonged
growing season with high ambient temperatures. The limited amount of emergent
vegetation, predominantly cattails (Typha sp.), in Lake Apopka may limit insect biomass.
The smallest growth rates of animals among the three lakes were found in Lake Apopka
hatchlings, perhaps because of low food availability.
Differences in growth rates among study areas were determined primarily by
differences in the thermoregulatory behavior of individuals, which appeared to be
inherited (Sinervo 1990). Water temperatures differed among lakes and, thus, affected
growth period. Therefore, differences in growth rate of hatchling alligators may be
related to temperature differences. Nonetheless, the growth rate in this study (Table 7)
was higher than that reported by Fuller (1981) in North Carolina (12.4 cm/yr) and
Dalrymple (1996) in south Florida (13.6 cm/yr). Ambient temperature in North Carolina
was very low compared to Florida. Consequently, the period of growth days was limited
to six months while it is at least eight months in central Florida. In an earlier study on
captive-reared hatchling alligators, growth rates of 0.2 cm/day for the first year were
recorded (Joanen and McNease 1970).
This study showed that growth rates of males were not different from females.
The difference in weight and length gain was not detected between sex during their first
year of age. In Louisiana, differences in growth rates of alligators were not significant
until juveniles reach 60 cm SVL (Nichols et al., 1976). As described in Deitz (1979),
Wilkinson and Rhodes (1997), Brandt (1991), and Elsey et al. (1992), male and female
hatchling alligators have equal growth rate in their early years. No correlation was
obtained for initial hatchling size and % increase in body weight. The results indicated
that size based dominance is not an important factor determining hatchling growth.
Because associated adult alligators were sighted with pods in all treatments and
growth rates were not different between wild and repatriated pods, it can be inferred that
all pods might have about the same level of stress associated with lack of associated
maternal female alligators. This results in chronically elevated plasma corticosterone.
Plasma corticosterone showed a strong negative correlation with change in body weight;
the lower the hormone levels, the faster the rate of growth (Elsey et al. 1990).
The survival rate shown in Table 9 was not as high as any other studies in Florida
lakes (Deitz 1979, Woodward et al. 1987), possibly because losses of entire pods were
also included in the mortality rate estimate. Survival estimates of 12 month-old wild
hatchlings on Orange Lake was 41% (Woodward et al. 1987), and 30% (Deitz 1979).
Most hatchling pods remained near nest sites for at least 10 months following hatching as
described by (Deitz 1979). In this study, six missing pods were never found, although
over 200 m around the original release location was intensively searched. All of the
missing pods were repatriated pods although the best and equal effort was put on every
pod during recapture attempts. Mark-recapture data indicated that survival rate of tagged
wild alligators (29.3%) was 41% greater than that of repatriated alligators (20.74%).
It was possible that either emigration, or mortality, was responsible for the
missing 6 pods. Note that all missing pods were from repatriated hatchlings: GR-21N,
OR-9S, OR-36S, OR38-S, OR-6N, and OR-44N (Figures 2 and 3, Table 4). Though
three out of the six were the pods released at nest sites, other extraneous factors might
cause them to disperse; i.e., water level, habitat suitability, and food availability.
Droughts are thought to increase mortality of marsh alligators above that of lake
alligators (Nichols et al. 1976). Twelve hatchling pods were observed travelling
significant distances at the onset of winter season probably due to low water level. This
behavior was viewed as increasing hatchling mortality because of desiccation and
predation (Nichols et al. 1976). Fluctuating water levels concentrate alligator
populations and increase social conflict with consequent injuries (Deitz 1979).
Different survival rates among lakes could be due to differences in population
density, which may be regulated by intraspecific predation. Crocodilians have long been
known to be cannibalistic. For example, in the first canal of Haines Creek, east of Lake
Griffin, several 4-5 years old alligators were observed at the nest site of one missing pod
(GR-21N) just after the first winter (Figure 2). Cannibalism was suspected as a cause of
some mortality in juvenile alligators (Woodward et al. 1987). Similarly cannibalism may
remove 7.4-10.1% of juvenile alligator population on Orange Lake annually (Delany et
al. unpubl. data).
Since survival of tagged wild alligators was 41% greater than that of repatriated
alligators, I hypothesized that parental association contributed to survival of hatchlings in
their 1st year. Maternal behavior seems to be more likely during incubation and early
post-hatching period. Female presence was observed either by chance or because she
attempted to attend her young although it was difficult to estimate the size of big
alligators as well as telling the gender. Besides, repatriated hatchlings remained in
captivity for approximately 2 weeks, their survival skills such as searching behavior is
thought to be affected resulting in greater chance of mortality.
Preliminary data in this study clearly indicate that it is feasible to release
artificially hatched alligators back into the wild to supplement natural loss from
embryonic death, and that repatriated alligators will grow as well as wild alligators,
which presumably would enhance survivorship. Future studies should try to genetically
match up mother and/or father alligator and their young to verify that an observed adult
alligator is the parent of the pod. This work requires an extensive field experience to
handle large alligators as well as knowledge in microsatellite techniques.
Growth rates can be experimentally manipulated fairly easily in laboratory
determinations of growth dynamics, but in wild animals the factors, which determine
access to food, and hence growth, can be very complex. Growth of hatchling alligators
from different locales varied considerably. This study showed that repatriated hatchlings
grow as well as wild alligators. This can be advantageous, as growth can greatly affect
survivorship (Rootes 1989). Jacobsen and Kushlan (1989) suggest that if an alligator
grows slower, it will take longer to reach sexual maturity, and increase its susceptibility
to predation, disease and cannibalism.
This study showed that survival rate of repatriated hatchlings was lower than wild
hatchlings. However, while significant, this difference is small and is unlikely to have
any effect on the population dynamics of these alligators. Supplementing natural loss
from embryonic death by restocking hatchlings appears to be a valuable management tool
for Florida alligators. Although survivorship of naturally hatched alligators is greater
than that of repatriated hatchlings, the initial number of repatriated hatchlings is more
than wild hatchlings and equal growth rate may enhance survival of repatriated hatchlings
to sexual maturity. This study also showed that repatriated hatchlings released at nest site
and suitable habitat had similar growth and survival rates. Therefore, management of
Florida alligators may adjust releasing procedures to be more practical by releasing
hatchlings at suitable habitats. Continuation of this study plus genetic characterization to
individuate alligator families over the next several years should provide data to further
refine management practices, with emphasis on recommendations for techniques in
selecting repatriating sites and optimum size at which to release juveniles.
Addison, B. G., Jr. 1993. Survival and movement of farm-raised alligators released in
a fresh water marsh in southeastern Louisiana. M.S. Thesis, Louisiana State Univ.,
Baton Rouge. 79pp.
Allsteadt, J., and J. W. Lang. 1995. Sexual dimorphism in the genital morphology of
young American alligators, Alligator missisippiensis. Herpetologica. 51(3):314-
Andrews, R. M. 1982. Patterns of growth in reptiles. Pages. 273-320 in: C. Gans and
F. H. Pough, eds. Biology of the Reptilia. Vol. 13. Physiology D--physiological
ecology. Academic press, New York, N.Y.
Bellairs, R. 1971. Developmental processes in higher vertebrates. Univ. of Miami
Press, Coral Gables, Florida. 366pp.
Brandt, L. A. 1991. Growth of juvenile alligators in Par Pond, Savannah River Site,
South Carolina. Copeia 4:1123-1129.
Brezonik, P. L. and E. E. Shannon. 1971. Trophic state of lakes in north-central
Florida. Florida Water Resources Res. Ctr., Publ. No. 13. 102pp.
Carr, A. F. 1976. Excerpts from the life of an alligator: A reappraisal of "The
Alligator's Life History." Foreword to McIlhenny, E. A., 1935. The alligator's life
history. Facsimile reprint, Society for the study of Amphibians and Reptiles Misc.
Chabreck, R. H. 1965. Methods of capturing, marking and sexing alligators. Proc.
Annu. Conf. Southeast. Assoc. Game and Fish Comm. 17:47-50.
1971. The foods and feeding habits of alligators from fresh and saline
environments in Louisiana. Proc. Annu. Conf. Southeast. Assoc. Game and Fish
Chabreck, R. H., and T. Joanen 1979. Growth rates of American alligators in
Louisiana. Herpetologica 35:51-57.
Chabreck, R. H., V. L. Wright, and B. G. Addison, Jr. 1998. Survival indices for farm-
released American alligators in a freshwater marsh. Pages 293-304 in: Crocodiles
Proc. fourteenth meeting of the Crocodile Specialist Group, IUCN The World
Conservation Union, Gland, Switzerland and Cambridge UK.
Conrow, R., W. Godwin, M. F. Coveney, and L. E. Battoe. 1993. SWIM plan for Lake
Apopka. St. Johns River Water Management District, Palatka, Florida. 163pp.
Cott, Hugh B. 1971. Parental care in the crocodilia, with special reference to
Crocodylus niloticus. IUCN Publ. New Series, Suppl. Paper No. 32:166-180.
Coulson, R. A., and T. Hernandez. 1983. Alligator metabolism: Studies on chemical
reactions in vivo. Pergamon, Oxford. 182pp.
Dalrymple, G. H. 1996. Growth of American alligators in the Shark Valley Region of
Everglades National park. Copeia 1996(1):212-216.
Deitz, D. C. 1979. Behavioral ecology of young American alligators. Ph.D.
Dissertation, Univ. of Florida, Gainesville. 151pp.
and D. R. Jackson. 1979. Use of American alligator nests by nesting turtles. J.
Deitz, D. C., and T. C. Hines. 1980. Alligator nesting in north-central Florida. Copeia
Elsey, R. M., T. Joanen, L. McNease, and V. Lance. 1990. Growth rate and plasma
corticosterone levels in juvenile alligators maintained at different stocking
densities. J. Exp. Zool. 255:30-36.
Elsey, R. M., T. Joanen, L. McNease, and N. Kinler. 1992. Growth rates and body
condition factors of Alligator mississippiensis in coastal Louisiana wetlands: A
comparison of wild and farm-released juveniles. Comp. Biochem. Physiol.
Emery, L., and R. S. Wydoski. 1987. Marking and tagging of aquatic animals: an
indexed bibliography. U.S. Fish and Wildl. Serv., Res. Publ. 165. 57pp.
Ferguson, M. W. J. 1981. The application of embryological studies to alligator
farming. Pages 129-145 in: P. Cardeilhac, T. Lane, and R. Larsen ,eds. Proc. First
annual alligator production conference. Inst. Food Agric. Sci., Univ. of Florida,
1982. In vivo and in vitro development of first brachial arch derivatives in
Alligator mississippiensis. Pages 275-286 in: A. D. Dixon and B. G. Sarnet, eds.
Factors and mechanisms influencing bone growth. Alan R. Liss, Inc., New York,
1985. Reproductive biology and embryology of the crocodilians. Pages 329-
491. in C. Gans, F. Billett, and P. Maderson, eds. Biology of the Reptilia. Vol. 14.
John Wiley and Sons, New York, N.Y.
Florida LAKEWATCH. 1996. Florida LAKEWATCH Data 1986-1996. Department
of Fisheries and Aquatic Sciences, University of Florida, Institute of Food and
Agricultural Sciences. Library, University of Florida. Gainesville, FL.
Fogarty, M. J. 1974. The ecology of the everglades alligators. Pages 367-374 in: P. J.
Gleason, ed. Environments of south Florida: present and past. Miami Geological
Society, Miami, FL
and J. D. Albury. 1967. Late summer foods of young alligators in Florida.
Proc. Annu. Conf. Southeast. Assoc. Game and Fish Comm. 21:220-222.
Fuller, M. K. 1981. Characteristics of an American alligator (Alligator
mississippiensis) population in the vicinity of Lake Ellis Simon, North Carolina.
Unpubl. M.S. Thesis, North Carolina State Univ., Raleigh.
Gorzula, S. J. 1978. An ecological study of Caiman crocodilus crocodilus inhabiting
savanna lagoons in the Venezuelan Guayana. Oecologia (Berl.) 35:21-34.
Garrick, L. D., and J. W. Lang. 1977. Social signals and behaviors of adult alligators
and crocodiles. Amer. Zool. 17:225-239.
Garrick, L. D., J. W. Lang, and H. A. Herzog, Jr. 1978. Social signals of adult
American alligators. Bull. Amer. Mus. Nat. Hist. 160(3):153-192.
Goodwin, T. M., and W. R. Marion. 1977. Occurrence of Florida red-bellied turtle
eggs in north-central Florida alligator nests. Fla. Sci. 40:237-238.
Goodwin, T. M., and W. R. Marion. 1978. Aspects of the nesting ecology of American
alligators (Alligator mississippiensis) in north-central Florida. Herpetologica
Graham, A. 1968. The Lake Rudolf crocodile (Crocodylus niloticus Laurenti)
population. Report to the Kenya Game Department by Wildlife Services Limited.
Hines, T. C., M. J. Fogarty and L. C. Chappell. 1968. Alligator research in Florida: A
progress report. Proc. Annu. Conf. Southeast. Assoc. Game and Fish Comm.
Huchzermeyer, F. W. 1997. Do crocodile hatchlings imprint on their parents? Croc.
Spec. Group Newsl. 16(1):21-22.
Hunt, R. H. 1975. Maternal behavior in the Morelet's crocodile, Crocodylus moreleti.
and M. E. Watanabe. 1982. Observations on maternal behavior of the
American alligator (Alligator mississippiensis). J. Herpetol. 16:235-239.
Jacobsen, T., and J. A. Kushlan. 1989. Growth dynamics in the American alligator
(Alligator mississippiensis). J. Zool. 219:309-328.
Jennings, M. L., H. F. Percival, and A. R. Woodward. 1988. Evaluation of alligator
hatchling and egg romoval from 3 Florida lakes. Proc. Annu. Conf. Southeast.
Assoc. Fish and Wildl. Agencies. 42:283-294.
Jennings, M. L., D. N. David, K. M. Portier. 1991. Effect of marking techniques on
growth and survivorship of hatchling alligators. Wildl. Soc. Bull. 19(2):204-207.
Joanen, T. 1969. Nesting ecology of alligators in Louisiana. Proc. Southeast. Assoc.
Game and Fish Comm. 23:141-151.
and L. McNease. 1970. A telemetric study of nesting female alligators on
Rockefeller Refuge, Louisiana. Proc. Annu. Conf. Southeast. Assoc. Game and
Fish Comm. 24:175-193.
Koelin, G. T., L. M. Cowardin, and L. L. Strong. 1994. Techniques for wildlife
habitats. Pages 540-566 in T. A. Bookhout, ed. Research and management
techniques for wildlife and habitats. The Wildlife Society, Bethesda, MD.
Kushlan, J. A. 1973. Observations on maternal behavior in the American alligator,
Alligator mississippiensis. Herpetologica 29:256-257.
and T. Jacobsen. 1990. Environmental variability and the reproductive
success of Everglades alligators. J. Herpetol. 24:176-184.
Kushlan, J. A., and M. S. Kushlan. 1980. Function of nest attendance in the American
alligator. Herpetologica 36:27-32.
Kushlan, J. A., and F. J. Mazzotti. 1989. Population biology of the American
crocodile. J. Herpetol. 23:7-21.
Lauren, D. J. 1985. The effect of chronic saline exposure on the electrolyte balance,
nitrogen metabolism and corticosterone titer on the American alligator (Alligator
mississippiensis). Comp. Biochem. Physiol. 81A:217-223.
LeCren, E. D. 1951. The length/weight relationship and seasonal cycle in gonad
weight and condition in the perch (Percafluviatilis). J. Anim. Ecol. 20:201-219.
Magnusson, W. E. 1995. Safe options for the management of crocodiles. Crocodile
Spec. Group Newsl. 14(4):3-5.
Magnusson, W. E., and T. M. Sanaiotti. 1995. Growth of Caiman crocodilus
crocodilus in centralamazonia, Brazil. Copeia 1995(2):498-501.
McIlhenny, E. A. 1935. The alligator's life history. Christopher Publishing House,
Metzen, W. D. 1978. Nesting ecology of alligators on the Okefenokee National
Wildlife Refuge. Proc. Southeast. Assoc. Game and Fish Comm. 31.
Modha, M. L. 1967. The ecology of the Nile crocodile on Central Island, Lake Rudolf.
E. Afr. Wildl. J. 5:74-95.
Moler, P. E. 1992. American crocodile recovery plan implementation. Final Perf. Rep.
Fla. Game and Fresh Water Fish Comm., Tallahassee. 34pp.
Murphy, T. M. 1977. Distribution, movement, and population dynamics of the
American alligator in a thermally altered reservoir. M.S. Thesis, Univ. Georgia,
Nichols, J. D., and K. H. Pollock. 1983. Estimation methodology in contemporary
small mammal capture-recapture studies. J. Mammal. 64:253-260.
Nichols, J. D., L. Viehman, R. H. Chabreckand B. Fenderson. 1976. Simulation of a
commercially harvested alligator populationin Louisiana. Louisiana Agricultural
Experimental Station Bulletin 691, Baton Rouge, LA.
Northcutt, R. G., and J. E. Heath. 1971. Performance of caimans in a T-maze. Copeia
Norusis, Marija J. 1991. The SPSS guide to data analysis for SPSS/PC+. SPSS
Inc.,Chicago, IL. 499pp.
Pooley, A. C. 1977. Nesting opening response of the Nile crocodile, Crocodylus
niloticus. J. Zool. London. 182:17-26.
Reese, A. M. 1915. The alligator and its allies. G. P. Putnam's Sons, NY, 358pp.
Sinervo, B. 1990. Evolution of thermal physiology and growth rate between
populations of the western fence lizard (Sceloporus occidentalis). Oecologia
Taylor, D., and Neal W. 1984. Management implications of size-class frequency
distributions in Louisiana alligator populations. Wildl. Soc. Bull. 12:312-318.
Taylor, J. A. 1979. The foods and feeding habits of subadult Crocodylus porosus
Schneider in Northern Australia. Aust. Wildl. Res. 6:347-359.
U.S. EPA. 1979. Environmental impact statement. Lake Apopka restoration project,
Lake and Orange Counties Florida. United States EPA, Region 4, Atlanta, GA.
Voelkl, E. K., and S. B. Gerber. 1999. Using SPSS for Windows: data analysis and
graphics. Springer-Verlag New York, Inc., New York, NY. 228pp.
Watanabe, M. E. 1980. The ethology of the American alligator (Alligator
mississippiensis) with emphasis on vocalizations and responses to vocalizations.
Ph.D. Dissertation, New York Univ., New York.
Webb, G. J. W., S. C. Manolis, P. J. Whitehead, and K. Dempsey. 1987. The possible
relationship between embryo orientation, opaque banding and the dehydration of
albumen in crocodile eggs. Copeia 1987:252-257.
Webb, G. J. W., P. G. Bayliss, and S. C. Manolis. 1989. Population research on
crocodiles in the Northern Territory, 1984-1986. Pages 22-59 in Proc. eighth
meeting of the Species Survival Comm., IUCN, Crocodile Specialist Group.
Woodward, A. R., T. C. Hines, C. L. Abercrombie, and J. D. Nichols. 1987. Survival
of young American alligators on Florida lake. J. Wildl. Manage. 51(4):931-937.
Woodward, A. R., M. L. Jennings, and H. F. Percival. 1989. Egg collecting and hatch
rates of American alligator eggs in Florida. Wildl. Soc. Bull. 17:124-130.
Woodward, A. R., H. F. Percival, M. L. Jennings, and C. L. Moore. 1993. Low clutch
viability of American alligators on Lake Apopka. Fla. Sci. 56:52-63.
Wilkinson, P. M., and W. E. Rhodes. 1997. Growth rates of American alligators in
coastal South Carolina. J. Wildl. Manage. 61(2):397-402.
Yosapong Temsiripong was born October 4, 1975, in Bangkok, Thailand. His
family moved to the Sriracha district, a suburban area, where his admiration for wildlife
started to develop. Favorite activities included camping, bird watching, fishing, and
many out-door activities. His commitment to wildlife began when he joined the
Environmental Conservation Organization. He made many trips to rain forests in
Yos's interests remained constant through a high school, which led him to
Kasetsart University, where he pursued a Bachelor of Science degree in zoology,
graduating in 1996. Yos began investigating possible avenues to proceed with graduate
studies. A year after his graduation, he was admitted to a Master of Science program in
the Department of Wildlife Ecology and Conservation, University of Florida.
His present goals include continuing his education in any form available to him.
With his working and training experiences both in his father's crocodile farm with
Siamese crocodiles (Crocodylus siamensis) and at Wildlife Research Lab, Florida Fish
and Wildlife Conservation Commission (FWC) with American alligators (Alligator
mississippiensis), he should have sufficient knowledge to continue exploring the
biological world. He also hopes to be able to share his love and appreciation for
Florida's wildlife, especially American alligators, with his children, continuing a family