Title: Growth and survival rates of wild and repatriated hatchling American alligators (Alligator mississippiensis) in central Florida lakes
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Title: Growth and survival rates of wild and repatriated hatchling American alligators (Alligator mississippiensis) in central Florida lakes
Physical Description: Book
Language: English
Creator: Temsiripong, Yosapong, 1975-
Publisher: State University System of Florida
Place of Publication: <Florida>
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Publication Date: 1999
Copyright Date: 1999
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Subject: Wildlife Ecology and Conservation thesis, M.S   ( lcsh )
Dissertations, Academic -- Wildlife Ecology and Conservation -- UF   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
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Summary: ABSTRACT: 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.
Summary: KEYWORDS: alligator, Florida, growth, repatriation, survival
Thesis: Thesis (M.S.)--University of Florida, 1999.
Bibliography: Includes bibliographical references (p. 49-54).
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Statement of Responsibility: by Yosapong Temsiripong.
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General Note: Document formatted into pages; contains xi, 55 p.; also contains graphics (some colored).
General Note: Vita.
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Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
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Resource Identifier: oclc - 45293710
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GROWTH AND SURVIVAL RATES OF WILD AND REPATRIATED HATCHLING
AMERICAN ALLIGATORS (Alligator mississippiensis) IN CENTRAL FLORIDA
LAKES













BY

YOSAPONG TEMSIRIPONG


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


1999






























Copyright 1999

by

Yosapong Temsiripong















ACKNOWLEDGMENTS


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




ACKNOWLEDGEMENTS....................................................................... iii

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

v









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


Table page

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


Figure page

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
LAKES

By

Yosapong Temsiripong

December 1999

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.















INTRODUCTION


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

hatchlings.

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








2
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,








3
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







5
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







6
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.















STUDY AREAS


Lake Apopka

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







8
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

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

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

increasing.










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Figure 2. Satellite imagery of Lake Griffin, Florida with alligator pod number and
location.


















MATERIALS AND METHODS


Egg Collection

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







14
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

Commission, Gainesville.

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).



Egg Incubation

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
and treatment.

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







17
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.



Post-Hatching Observation

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.









Recapture

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







19
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).



GIS Technology

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).



Data Analyses

Growth Rate

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),







20
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.

TL2 TLi
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

SVL2 SVLi
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

1979).









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










30

28










18 :'..""...1!/. LAKE
o 16 .Apopka
24










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

16 Apopka

14 i.. ,Griffin
12 Orange



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

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

alligators.



Statistical Methods

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







24
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.















RESULTS


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-

recaptured study.



Post-Hatching Observation

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







26
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).







27

Table 4. Movement summary during recapture of hatchling American alligators in
central Florida lakes.


Lake

Apopka

Apopka

Apopka

Griffin

Griffin

Griffin

Griffin

Orange

Orange

Orange

Orange

Orange

Orange

Orange

Orange

Orange

Orange

Orange


Pod No.

AP-508W

AP-601W

AP-12N

GR-28N

GR-21N

GR-13S

GR-34S

OR-506W

OR-510W

OR-6N

OR-20N

OR-44N

OR-106N

OR-9S

OR-13S

OR-36S

OR-38S

OR-110S


Original location

28'37.310"/81'41.070"

28'40.770"/81'38.710"

28'37.240"/81'41.010"

28'55.870"/81 '49.990"

28'53.590"/81'49.560"

28'53.400"/81'49.760"

28'56.320"/81'49.730"

29'29.066"/82'10.580"

29'28.137"/82'10.069"

29'25.566"/82'11.140"

29'26.619"/82'07.896"

29'26.000"/82'08.580"

29'28.880"/82'10.100"

29'25.750"/82'11.610"

29'26.421"/82'09.026"

29'25.722"/82'10.667"

29'27.270"/82'11.970"

29'28.730"/82'10.010"


Last location

28'37.269"/81'41.067"

28'40.771"/81'38.724"

28'37.264"/81'40.979"

28'55.844"/81'49.978"

N/A

28'53.365"/81'49.766"

28'56.342"/81'49.745"

29'29.058"/82'10.603"

29'28.189"/82'10.056"

N/A

29'26.682"/82'07.936"

N/A

29'28.855"/82'10.039"

N/A

29'26.427"/82'09.035"

N/A

N/A

29'28.763"/82'09.970"


Dispersal (m)

75.1

25.1

125.4

26.5

Missing pod

52.9

74.8

94.9

105.3

Missing pod

118.2

Missing pod

112.8

Missing pod

63.5

Missing pod

Missing pod

127.1


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

airboat

OR-506W Orange 2320 7'-8' alligator submerged as we approached, kept 10 m

observation distance

OR-45N Orange 2345 7' alligator submerged immediately as we approached

OR-126N Orange 2125 7' alligator submerged shortly after we shined light on

her

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

hatchling grunts

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









Growth Rate

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.


Median

Lake recapture date No. of pod


Wild hatchlings

TL (cm)1 TL (cm/day)2


Repatriated hatchlings

Released at Nest site Released in Suitable habitat

TL (cm)1 TL (cm/day)2 TL (cm)1 TL (cm/day)2


0.076 0.02

0.081 0.02

0.159 0.05

0.100 0.05


15.24

19.98

19.41

17.65


0.075 0.01

0.083 0.01

0.103 0.03

0.086 0.02


15.64

18.99

22.51

20.16


0.079 0.01

0.080 0.01

0.107 0.04

0.095 0.03


** (P < 0.01)
1 Average 10 month increase in total length (TL)
2 Average 10 month increase in total length change per growth day


Apopka

Griffin

Orange

Average


June 25th

June 14th

July 2nd


15.67

19.88

40.73

24.03















.13

n=22
>, .12



I .11

n=50
.10


.09


.08


.07

Wild Repatriated
Hatchling Hatchling

Treatment



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).




















n=-6







n=8
n8-
Ii8 ------


Wild
Hatchling


n=7


n=5
n=10 --,---

.r...............


Repatriated hatchling
at the nest site


n=16

n=5 7
n=7
_hq


Repatriated hatchling
in the suitable habitat


Treatment



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.


LAKE

I
] Apopka



r. Griffin



Orange















.20

.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


.10.
13 *Eb 0 3 D3 D0 03


S.06 0 [ 0

.04 0
0
.02 1:
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

treatments.



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







36
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

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.


Lake

Apopka

Griffin

Orange

Average

* (P = 0.028)


Wild hatchlings

0.28 0.14

0.31 0.08

0.29 0.22

0.29 0.14*


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


Overall mean

0.25 0.13

0.21 0.12

0.23 0.19

0.23 0.16


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


Lake Apopka

Lake Griffin

Orange Lake

Overall


1.0

0.95

0.85

0.92















0.41

n=22




0.3.


Sn56



0 2 .






0.1

Wild Hatchling Repatriated Hatchling

Treatment





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.









40





0.4,






n=25 n=34
0.3,
n=19





0.2,






0.1

Apopka Griffin Orange

Lake




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.

















0.7'


0.6, y = 30.3948-0.3369x
R2= 0.033

0.5. n = 78
P = 0.113
0.4, D D
E 0.3.

a 0 0 00 3
0 13 13 13 03 3



oo o

0 0
0.12 0 0




-0.1
0 10 20 30 40 50


Clutch Size



Figure 10. Relationship of survival rate of hatchling American alligators to clutch size
in central Florida lakes.















DISCUSSION


Growth Rate

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







43
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







44
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).



Survival Rate

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







45
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







46
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.















CONCLUSION


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







48
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.















REFERENCES


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-
325.

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.
Publ.

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
Comm. 25:117-124.

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.
Herptol. 13:510-512.

Deitz, D. C., and T. C. Hines. 1980. Alligator nesting in north-central Florida. Copeia
1980:249-258.

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.
103A:667-672.

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,
Gainesville.

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,
N.Y.









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
34:43-47.

Graham, A. 1968. The Lake Rudolf crocodile (Crocodylus niloticus Laurenti)
population. Report to the Kenya Game Department by Wildlife Services Limited.
145pp.

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.
22:166-180.

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.
Copeia 1975(4):763-764.

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,
Boston. 117pp.

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,
Athens.

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
1971(3):557-560.

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
83:228-237.

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.
445pp.

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.















BIOGRAPHICAL SKETCH


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

Thailand.

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

tradition.




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