• TABLE OF CONTENTS
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 Title Page
 Acknowledgement
 Introduction
 Study area
 Methods
 Results and discussion
 Literature cited






Group Title: Florida Cooperative Fish and Wildlife Research Unit Technical report no. 29
Title: Evaluation of alligator hatchling and egg removal from 3 Florida lakes
CITATION PAGE IMAGE ZOOMABLE
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00073831/00001
 Material Information
Title: Evaluation of alligator hatchling and egg removal from 3 Florida lakes
Series Title: Technical report
Alternate Title: Alligator hatchling and egg removal
Physical Description: 65 leaves : ill., maps ; 28 cm.
Language: English
Creator: Percival, H. Franklin ( Henry Franklin )
Jennings, Michael L
Florida Cooperative Fish and Wildlife Research Unit
Florida Alligator Farmers Association
Florida -- Game and Fresh Water Fish Commission
University of Florida
Publisher: Cooperative Fish and Wildlife Research Unit, Dept. of Wildlife and Range Sciences, School of Forest Resources and Conservation
Place of Publication: Gainesville FL
Publication Date: [1987?]
 Subjects
Subject: American alligator -- Collection and preservation -- Environmental aspects -- Florida   ( lcsh )
American alligator -- Reproduction -- Florida   ( lcsh )
American alligator -- Eggs -- Florida   ( lcsh )
Alligators -- Collection and preservation -- Environmental aspects -- Florida   ( lcsh )
Wild animal collecting -- Environmental aspects -- Florida   ( lcsh )
Reptile populations -- Florida   ( lcsh )
Alligator farming -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by H. Franklin Percival and Michael L. Jennings.
General Note: Cover title.
General Note: "Final report submitted by: Cooperative Fish and Wildlife Research Unit, Department of Wildlife and Range Sciences, School of Forest Resources and Conservation, University of Florida .... Supported by Florida Alligator Farmers Association, Florida Game and Fresh Water Fish Commission, U.S. Fish and Wildlife Service, University of Florida."
General Note: "April 1987."
Funding: This collection includes items related to Florida’s environments, ecosystems, and species. It includes the subcollections of Florida Cooperative Fish and Wildlife Research Unit project documents, the Sea Grant technical series, the Florida Geological Survey series, the Coastal Engineering Department series, the Howard T. Odum Center for Wetland technical reports, and other entities devoted to the study and preservation of Florida's natural resources.
 Record Information
Bibliographic ID: UF00073831
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved, Board of Trustees of the University of Florida
Resource Identifier: aleph - 001894757
oclc - 27959889
notis - AJX0022

Table of Contents
    Title Page
        Title page
    Acknowledgement
        Page 1
    Introduction
        Page 1
        Page 2
    Study area
        Page 3
        Page 4
    Methods
        Page 5
        Removal rate
            Page 5
        Nest production and success
            Page 6
            Page 7
        Hatchling/egg removal
            Page 8
            Page 9
            Page 10
        High-light counts
            Page 11
            Page 12
            Page 13
            Page 14
            Page 15
            Page 16
            Page 17
            Page 18
            Page 19
        Cost-benefit ration of egg and hatchling collection
            Page 20
    Results and discussion
        Page 21
        Early age-class removal
            Page 21
        Nest production and success
            Page 22
            Page 23
            Page 24
            Page 25
            Page 26
            Page 27
            Page 28
            Page 29
            Page 30
            Page 31
            Page 32
        Night-light counts
            Page 33
            Page 34
            Page 35
            Page 36
            Page 37
            Page 38
            Page 39
            Page 40
            Page 41
            Page 42
            Page 43
            Page 44
            Page 45
            Page 46
            Page 47
            Page 48
            Page 49
        Cost-benefit ration of collecting wild production
            Page 50
            Page 51
            Page 52
            Page 53
            Page 54
            Page 55
        Nesting parameters
            Page 56
            Page 57
            Page 58
            Page 59
        Conclusion
            Page 60
            Page 61
        Recommendations
            Page 62
            Page 63
    Literature cited
        Page 64
        Page 65
        Page 66
Full Text





TECHNICAL REPORT NO. 29








EVALUATION OF ALLIGATOR HATCHLING AND EGG
REMOVAL FROM 3 FLORIDA LAKES


H. Franklin Percival
and
Michael L. Jennings








Final Report Submitted by:
Cooperative Fish and Wildlife Research Unit
Department of Wildlife and Range Sciences
School of Forest Resources and Conservation
University of Florida
Gainesville, FL 32611




Supported by:

Florida Alligator Farmers Association
Florida Game and Fresh Water
U. S. Fish and Wildife Service
Univeristy of Florida


April 1987


r'








ACKNOWLEDGEMENTS


The Florida Cooperative Fish and Wildlife Research Unit, Florida

Game and Fresh Water Fish Commission, and the Florida Alligator Farmers

Association jointly supported this research project. C. Abercrombie, A.

Woodward, and T. Hines assisted in developing the frame work for data

collection and interpretation. D. Ashley, and members of the Florida

Alligator Farmers Association provided financial support, equipment,

facilities and personnel. D. David, M. Delany, C. McKelvy, J. White, L.

Hord, G. Holder, T. Reagan, T. Stice, J. Defazio, A. Bush, J. Clugston

assisted in data collection. D. Carlberg provided flawless helicopter

service when requested. We extend our gratitude to these institutions

and people and to the many others who contributed voluntary assistance.






INTRODUCTION

The ranching of eggs and juveniles is an important aspect of

successful crocodilian management programs throughout the world. In

1972, Papua New Guinea began its commercial ranching program which

currently harvests wild Crocodylus porosus and C. novaegineae juveniles

for captive rearing (Rose 1982, National Resource Council 1983). In

Zimbabwe, C. niloticus eggs are collected from wild nests and incubated

and reared on farms. Similarly, in Louisiana, Alligator

mississippiensis eggs are collected and incubated by the Louisiana

Wildlife and Fisheries Commission and then distributed to qualified

alligator farms. Governments in Australia, Africa, Asia, Central








ACKNOWLEDGEMENTS


The Florida Cooperative Fish and Wildlife Research Unit, Florida

Game and Fresh Water Fish Commission, and the Florida Alligator Farmers

Association jointly supported this research project. C. Abercrombie, A.

Woodward, and T. Hines assisted in developing the frame work for data

collection and interpretation. D. Ashley, and members of the Florida

Alligator Farmers Association provided financial support, equipment,

facilities and personnel. D. David, M. Delany, C. McKelvy, J. White, L.

Hord, G. Holder, T. Reagan, T. Stice, J. Defazio, A. Bush, J. Clugston

assisted in data collection. D. Carlberg provided flawless helicopter

service when requested. We extend our gratitude to these institutions

and people and to the many others who contributed voluntary assistance.






INTRODUCTION

The ranching of eggs and juveniles is an important aspect of

successful crocodilian management programs throughout the world. In

1972, Papua New Guinea began its commercial ranching program which

currently harvests wild Crocodylus porosus and C. novaegineae juveniles

for captive rearing (Rose 1982, National Resource Council 1983). In

Zimbabwe, C. niloticus eggs are collected from wild nests and incubated

and reared on farms. Similarly, in Louisiana, Alligator

mississippiensis eggs are collected and incubated by the Louisiana

Wildlife and Fisheries Commission and then distributed to qualified

alligator farms. Governments in Australia, Africa, Asia, Central








America, and South America currently are investigating the feasibility

of commercial ranching of crocodiles.

Though the concept of juvenile or egg harvests is not new,

uncertainties exist regarding short and long-term impacts on harvested

populations. In Florida, where demand for alligator young and eggs is

expanding, identification of potential biological impacts associated

with future management programs is imperative. Florida's harvest

program has been based on an experimental study which evaluates the

biological impact of removal.

Our concept of alligator ranching assumes that harvest rates of

eggs and juveniles depends largely on the degree to which compensatory

mechanisms function in alligator populations. That not all production

is necessary to maintain populations indicates that density independent

and density dependent mechanisms are functioning in alligator

populations from the egg stage through the first few years of life. The

nature of the effects of these mechanisms on populations ultimately will

provide a guide for management decisions regarding future harvest

programs.

The primary objective was to evaluate the impacts on alligators

populations when 50% of the annual production was removed from 3 study

sites in central Florida. Specific research objectives of this study

were to: (1) compare clutch size, fertility, hatchability rates for each

clutch from each study area; (2) evaluate growth rates of early

age-class alligators from all treatment lakes and control area Lake

Woodruff; and (3) document changes in population size and structure on

the study areas.







STUDY AREAS
Study areas were selected based on the following criteria: (1)

they should contain relatively dense alligator populations such that any

changes in population demography could be adequately quantified; (2)

they should contain at least superficial similarities in terms of basin

type, hydrological characteristics and marsh plant communities; and (3)
adequate nesting should exist to satisfy sample size requirements for

nesting studies ( 50 nests/year). Thus, Lakes Griffin, Jessup, and

Apopka were chosen as treatments and Lake Woodruff selected as a

control. Paynes Prairie was utilized as a control only for evaluating

annual variations in nesting.

Lakes Griffin (5860 ha) and Apopka (12141 ha) are eutrophic,
hardwater natural lakes with unconsolidated substrates in the Oklawaha

chain of lakes within the central valley physiographic region of Florida

(Canfield 1981). Lake Griffin receives water primarily through rainfall

and the canals connecting it with Lake Yale and Lake Eustis. It drained

to the north through the Oklawaha River. The southern half of shoreline

is highly developed, while much of the east central marsh has been

drained and cleared for vegetable farming and improved pasture. Bottom

substrates include muck and sand, supporting very little submergent or

emmergent vegetation. Most of the 3815 ha of wooded marsh occurs in a

narrow band proximal to open water areas in the northern half of the

lake and is characterized by Carolina willow (Salix caroliniana), wax
myrtle (Myrica cerifera), red maple (Acer rubrum), blackberry (Rubus
rubripes), and elephant ear (Colocasia esculentum). A true wet marsh

(4265 ha) occurs outside this association characterized by sawgrass
(Cladium jamaicense), maidencane (Panicum hemitomon), cinnomon fern







(Osmunda cinnamomea), sedges (Carex spp.), and rushes (Juncus spp.).
Lake Apopka receives water from rainfall, runoff and springs and
draines northward through the Beauclair canal. Pumps re-circulate water
for agricultural purposes in the former northern marshes. About 96% of
Lake Apopka's northern marsh (13000 ha) was diked and drained in the
1940's for agricultural purposes. The small remnant (543 ha) of the
original marsh is dominated by Carolina willow and arrowhead (Sagittaria
lancifolia). Surrounding much of the remaining shoreline is wooded
marsh (3988 ha) comprised of swamp tupelo (Nyssa sylvatica), bald

cypress (Taxodium distichum), red maple, Carolina willow, wax myrtle,
and arrowhead.
Lakes Jessup (4452 ha) and Woodruff (2429 ha) are eutrophic,
alkaline, natural lakes, with unconsolidated substrates in the St.
John's River drainage system in east central Florida (Canfield 1981).

Much of Lake Jessup's western shore has been cleared and converted to
improved pasture. The undisturbed northeastern marsh (5843 ha) is
dominated by sand cordgrass (Spartina bakeri) and giant reed (Phragmites

australis), whereas the wooded southern marsh (1673 ha) contains bald
cypress, swamp tupelo, and red maple. Water levels are regulated by
hydrological fluctuation in the St. John's River.
Lake Woodruff and its surrounding marsh were incorporated into a
National Wildlife Refuge in 1964 and have not been developed. Logging

dikes constructed during the 1950's surround much of Lake Woodruff's
perifery and provide borrow pits and support for sweetgum (Liquidambar
styraciflua), swamp tupelo, red maple, Carolina willow and bald cypress.
The remaining wooded marsh contains naturally occurring tree islands and
wooded sloughs. Beyond the spoil berms, vast expanses (1214 ha) of sand







cordgrass dominate. Unlike the other study areas, Lake Woodruff

supports significant submergent plant growth, principally banana

waterlily (Ceratophyllum demersum) and eel grass (Vallisneria ,
americana). Water inflow and outflow from Lake Woodruff are regulated

primarily by fluctuations in the St. John's River.

Paynes Prairie is a 8599 ha shallow, emergent marsh with only 605

ha of open water (Alachua Lake). Its substrate is composed of deep

organic material which supports growths of water loosestrife (Decodon

verticillatus), water primrose(Ludwigia peruviana), maiden cane, cattail

(Typha latifolia) and pickerelweed (Pontederia lanceolata). Paynes
Prairie receives water through lateral permeability of the Florida

Aquifer, rainfall and runoff from Gainesville and is drained by a

natural sink on the northeastern shoreline. Water is regulated by a

network of dikes and control structures. The dikes support upland

plants and wood vegetation (e.g. waxmyrtle and Carolina willow). Two

major highways (U.S. 441 and 1-75) traverse the system from north to

south in its western portion.


METHODS


Removal Rate

Experimental removal rates were evaluated for their potential

impacts on alligator populations. Specifically, we were interested in

targeting the total surviving production on each study area. This

required adjustments of production estimates to account for natural

mortality due to predation. We felt that a 50% removal rate on

surviving hatchlings and nests was high enough to impact populations but







cordgrass dominate. Unlike the other study areas, Lake Woodruff

supports significant submergent plant growth, principally banana

waterlily (Ceratophyllum demersum) and eel grass (Vallisneria ,
americana). Water inflow and outflow from Lake Woodruff are regulated

primarily by fluctuations in the St. John's River.

Paynes Prairie is a 8599 ha shallow, emergent marsh with only 605

ha of open water (Alachua Lake). Its substrate is composed of deep

organic material which supports growths of water loosestrife (Decodon

verticillatus), water primrose(Ludwigia peruviana), maiden cane, cattail

(Typha latifolia) and pickerelweed (Pontederia lanceolata). Paynes
Prairie receives water through lateral permeability of the Florida

Aquifer, rainfall and runoff from Gainesville and is drained by a

natural sink on the northeastern shoreline. Water is regulated by a

network of dikes and control structures. The dikes support upland

plants and wood vegetation (e.g. waxmyrtle and Carolina willow). Two

major highways (U.S. 441 and 1-75) traverse the system from north to

south in its western portion.


METHODS


Removal Rate

Experimental removal rates were evaluated for their potential

impacts on alligator populations. Specifically, we were interested in

targeting the total surviving production on each study area. This

required adjustments of production estimates to account for natural

mortality due to predation. We felt that a 50% removal rate on

surviving hatchlings and nests was high enough to impact populations but







low enough to insure that drastic population declines would not occur.

Further, a 50% removal was considered the maximum work load that could

be efficiently implemented and managed.


Nest Production & Success

Nest surveys were conducted from 5-25 July each year to determine

total nesting effort. Helicopters were used in 1981, and 1983-1986. A

fixed wing aircraft modified for slow flight (approximately 96 kph) also

was used to search for nests in 1982. Helicopter survey altitude was

maintained at 30 to 50 m except when nest status determination required

hovering 5 to 20 m above nests. Survey routes were flown parallel with

the shoreline when marsh areas were narrow. In more extensive marsh

habitat parallel routes approximately 100 m apart were traversed. All

potential nesting habitat was surveyed.

Nest locations and their status (active, depredated, false,

flooded or unknown fate) were recorded during the initial survey on

aerial photographs. The second and third surveys were conducted to

determine nest status during late incubation (early August) and

post-hatching (late September) periods, respectively. Previously

undiscovered nests found during these two flights were documented

similarly to those on the initial survey. Unhatched nests observed

during the final survey were not utilized in analyses of nest mortality

because final fate could not accurately be estimated.

Active nests were distinguishable as intact domes approximately 1.5

m in diameter and 0.5 to 1.0 m in height (Joanen 1969, Campbell 1972).

Active nests located during post-hatching surveys were characterized as

having a semi-circular excavation from the top center down to the bottom







of the egg cavity (Deitz and Hines 1980). Depredated nests were
distinguished as being flattened with nest material scattered and
alligator eggs or shell fragments littering the immediate area. To
circumvent overestimation of depredation in years where clutches were
removed, 2 separate depredation rates were averaged. Overall
depredation rate (D ) was estimated by:

(DI/AI) + (D2/A2)


2
where: D1 = total number of aerially observed nests depredated prior to
clutch removal; Al = total nests aerially observed during first survey;
D2 = number of aerially sighted nest depredated after clutch removal

and; A2 = number nests remaining after egg removal. A2 was estimated

by:

(A1-D1)-R
where R = number of clutches removed. On Lake Woodruff and in years

where clutches were not removed from Lakes Griffin, Jessup, and Apopka,
depredation rates were calculated as the total number of nests

depredated throughout incubation divided by the total number of nests

aerially observed. Nests were considered flooded if submerged by
two-thirds or more. Positive identification of false nests varied among

wetland systems, but generally appeared smaller, often incomplete and in
most instances in close association with larger true nests. Some nests
lost identifiable visual characteristics, or were located in dense
vegetative cover which obscured visibility in later surveys. The final
status of these nests was considered to be in proportion to those nests
with known final status.







Total nesting estimates (N) were calculated by:

N = A+ H
where: A = the total number of air-sighted nests; and H = est-imate of

the number of nests not seen during aerial survey, where H was estimated

by:

H = P/D,

where: P = number of pods found during post hatch night-light survey

that were not associated with an air-sighted nest. We assumed that nest

success was independent of nest density and that the hatching success

rate for unobserved nests equalled observed nests.


Hatchling/Egg Removal

A 50% removal of production on the 3 treatment lakes was

accomplished by hatchling collection during the fall and spring of 1981

and 1982 nesting seasons, a combination of egg and hatchling collection

in 1983, and egg collection from 1984 1986.

Hatchling collections were initiated in early September after the

final aerial survey, continued through October, and resumed in March.

Night searches were conducted from airboats using Kohler wheat-lites

with 15,000 60,000 cp bulbs. Pods or sibling groups of hatchlings

were identified by the faint red reflection of the spotlight from their

eyes. After locating a pod, individuals were captured by hand or

Pilstrom tongs and placed in 5 gallon plastic buckets. When no more

hatchlings were sighted or could be heard (distress calling) the

location was inconspicuously marked with flagging tape and a plant tag

(10 mm X 70 mm) identifying the nest number. The location of the pod

was recorded on a Mark Hurd (1:2400) aerial photograph. These locations







were compared with those plotted during aerial surveys and provided
information on association of collected pods with air-sighted

nests. Some pod locations were revisited throughout the fall and spring
to collect hatchlings previously missed.

Upon completion of a search, hatchlings were tagged on the web of

the right rear foot between the 2nd and 3rd toes with a number 1 monel

tag bearing the inscription FSP (Farm Supplement Project) followed by a

4 digit number. For each pod, information on the number of hatchlings,

tag numbers, collection site characteristics, female behavior, and

environmental conditions was recorded. Hatchlings were transported to

alligator farms within 48 hours of collection.

In 1983 a portion of the targeted removal included taking eggs from

as many nests as could be located during ground searches. From

1984-1986 egg removal was the only technique used and required that nest

be visually located by helicopter. Ground crews in airboats were then

directed to nest locations via air-ground communications. Ground crews

collected information on nest size, relative humidity, estimated

percentage daily shade and status (dry, partially flooded or flooded),

female presence and behavior, nesting habitat and comments regarding

peculiarities of the nest site. After excavating the nest, clutch size,

and egg status (fertile, infertile, dry, partially flooded, flooded)

were recorded. Eggs were individually marked on their uppermost surface

with a felt-tipped waterproof marker to indicate their relative position

as they were removed from the nest. To reduce any potential toxicity of

the ink, eggs were not marked on the developmental band during 1985 and

1986. Eggs less than 25% inundated with water were considered dry and
marked with black ink; 25-75% inundated eggs were considered partially








flooded and marked red; and over 75% inundated eggs were considered

flooded and marked blue. Eggs then were positioned (set) in the

incubation trays (plastic bus pans 61 cm X 39 cm) such that relative

position in the nest cavity could be determined. The incubation pan was
filled with approximately 5 cm of natural nest material upon which eggs

were placed. The eggs were then covered with seasoned hay.

During transportation of the incubation tray extreme care was taken

to avoid excessive vibration or shock. In the majority of cases, one

individual was directed to hold the incubation tray to avoid contact

with any part of the boat while in transit (usually <1 km) to the egg

transport boat. The latter was a 16 foot Panther (the mention of

tradename does not constitute endorsement or recommendation for use by

the Federal government) aluminum airboat with the passenger seat removed

to accommodate the egg platform (five inflated tire inner tubes placed on

the floor of the airboat and sheets of 1/2" plywood and 2 inch foam

rubber separated layers of 10 egg trays). Where possible, the transport

boat was carefully maneuvered in sheltered waters to avoid excessive

vibration. Eggs were transported to incubators in a covered pickup

truck on the same cushioned platform. Temperatures were monitored to

insure that eggs were maintained between 280 and 32C during transport

to incubators.

After arrival at a farm, eggs were transilluminated to check for

fertility and egg band development (Ferguson 1981, Webb and Manolis

1987). Infertile eggs were identified by the lack of an opaque embryo

attachment spot or band and were discarded. If band development was

visibly retarded or if vascular pigmentation was not similar to that of

other apparently health eggs in the clutch, the egg in question was








opened and the status (strong, good, weak, or dead) of the embryo

recorded. One healthy egg was removed from each clutch and sacrificed

for determination of clutch age. In 1984 embryo age was estimated by

back-dating from the hatch date of each clutch. In 1985 and 1986 a

combination of back-dating, embryological development charts, and egg

banding (Ferguson 1981) were used to determine embryo age. Eggs were

transilluminated again approximately 3 to 4 weeks later to identify eggs

containing embryos that were originally missed or that had died since

the first check. Unhatched eggs from each clutch also were opened and

embryos checked for age at death.


Night-Light Counts

Night-light counts were used to evaluate population trends on all

study areas (Wood and Humphrey 1983). Most surveys were conducted

during late May and June, 1980-1986 with airboats or outboard motor

boats. One survey per year was conducted on Lakes Griffin and Apopka

from 1980-1982, and on Lakes Jessup and Woodruff from 1981-1982. Two

replicate surveys were conducted on all lakes from 1983-1986 with the

exception of only one survey on Lake Griffin during 1985. The replicate

surveys were conducted within a 1 month period to reduce variation of

environmental factors such as air and water temperature, and water

levels (Woodward and Marion 1979).

Standard survey routes (Figs. 1, 2, 3, 4) were run with a 200,000

cp light to detect alligator eye reflections. Once spotted, each animal

was approached and its size estimated in 1 ft. length categories.

Animals that submerged or were not clearly visible (dense vegetation)

were classified in general size classes 0-2, 2-4, 4-6, and 6+ feet. In






















Standard night-light alligator survey route followed on Lake
Griffin from 1981-1986.


Figure 1.






















1600 m



.--- 1600 m


LAKE


GRIFFIN




















Standard night-light alligator survey route followed on Lake
Jessup from 1981-1986.


Figure 2.



















N


U3
"






















Figure 3. Standard night-light alligator survey route followed on Lake
Apopka from 1981-1986.




























LAKE APOPKA


* 3400




















Figure 4. Standard night-light alligator survey route followed on Lake
Woodruff from 1981-1986.
























LAKE


OODRUFF


- .1700 m








cases where only eye reflections were seen and no reliable estimate of

size could be obtained the observation was recorded as "unknown". Eye

reflections seen at the outer limits of the spot light (approximately

300 m beyond the transect line) were recorded as "not approached". For

analytical purposes, "unknown" and "not approached" categories were

divided into the 1 foot categories based on the proportions of animals

occurring in those known size classes. Total length estimates were based

on the relationship that snout-length in inches equalled total length in

feet. To calibrate estimates, several alligators were sized by sight

and then caught and measured prior to beginning surveys.

Log-transformed count data were analyzed for trends in size

composition (while accounting for the effects of water level as a

covariable) by dividing the number of known size alligators counted

during night surveys in each of 3 size classes (2-6, 4-6, and 2+ ft.) by

the total number of known-size alligators counted and transforming the

resulting proportions by an arcsin transformation. Regression analyses

were conducted on those transformed proportions to test the hypothesis

that size class composition changed during the study.

Evaluation of the 3 size classes was emphasized for those

categories in which harvested cohorts were likely to be represented.

The 2+ foot category was evaluated to better understand total population

response to other demographic and environmental factors.


Cost-Benefit Ratio of Egg and Hatchling Collection

Assessments of alligator egg and hatchling removal provided a

measure of the economic and biological viability of each procedure.

Evaluation of expenditures were based on actual incurred expenses.








Personnel time was estimated from work loads and average times for

completion of those jobs. A relative salary level of 6.00/hr remained

constant in the analysis of egg and hatchling removal. The salary level

was based on average projected needs for professional and technical

services. Salaries ranged from volunteers to individuals making

approximately $30.00/hr. Airboat expenses were based on average use of

airboat engine types. For example, boats with larger

engines were required during egg collection to traverse difficult

habitat, thereby increasing hourly costs over those used for hatchling

removal.

The information developed for this analysis was based on the 1982

hatchling removal on Lakes Griffin and Apopka (all nests on Lake Jessup

were flooded in that year) and the 1986 egg removal for Lakes Griffin ,

Apopka, and Jessup. Because of the experience level of personnel, those

collections reflect the most efficient strategy for both situations and

would be considered an accurate appraisal of minimum costs associated

with this study. These values should not be used to directly estimate

costs of potential management programs but instead are an estimate of

relative costs among habitat types, nesting densities, and collection

methods.


RESULTS & DISCUSSION


Early age-class removal

Over the course of this study, 4120 hatchlings and 17,039 fertile

eggs were removed from the 3 study areas. Lake Griffin was the most

productive lake, resulting in 2,161 hatchlings during 1981 and 1982 and








Personnel time was estimated from work loads and average times for

completion of those jobs. A relative salary level of 6.00/hr remained

constant in the analysis of egg and hatchling removal. The salary level

was based on average projected needs for professional and technical

services. Salaries ranged from volunteers to individuals making

approximately $30.00/hr. Airboat expenses were based on average use of

airboat engine types. For example, boats with larger

engines were required during egg collection to traverse difficult

habitat, thereby increasing hourly costs over those used for hatchling

removal.

The information developed for this analysis was based on the 1982

hatchling removal on Lakes Griffin and Apopka (all nests on Lake Jessup

were flooded in that year) and the 1986 egg removal for Lakes Griffin ,

Apopka, and Jessup. Because of the experience level of personnel, those

collections reflect the most efficient strategy for both situations and

would be considered an accurate appraisal of minimum costs associated

with this study. These values should not be used to directly estimate

costs of potential management programs but instead are an estimate of

relative costs among habitat types, nesting densities, and collection

methods.


RESULTS & DISCUSSION


Early age-class removal

Over the course of this study, 4120 hatchlings and 17,039 fertile

eggs were removed from the 3 study areas. Lake Griffin was the most

productive lake, resulting in 2,161 hatchlings during 1981 and 1982 and








8,349 fertile eggs from 1983-1986. Lakes Jessup and Apopka were less

productive resulting in the collection of 317 and 491 hatchlings, and

6,203 and 2,487 fertile eggs, respectively.

Inconsistencies in the collection techniques and variability in

habitat type among lakes probably resulted in underestimation of total

production during some years. Consequently, actual removal levels did

not always approach the targeted 50% level.


Nest Production and Success

Estimates of total nest production on all study lakes were

generally lower during 1981 and 1982 than all other years (Table 1).

Nest production and nest survival trends are considered herein only for

those years (1983-1986) in which reliable and consistent data were

collected from helicopter surveys.


Minimum Total Nesting -- Nesting estimates for Lake Griffin ranged

from a low of 95 during the 1984 drawdown (Fig 5) to a high of 166

during 1983 (Table 1). We considered the latter estimate to be the most

reliable assessment of total nesting effort because aerial survey

techniques had been standardized and sufficient capture-recapture work

was conducted during the fall to quantify pods not associated with

aerially observed nests. Therefore, total nesting estimates during 1981

and 1982 may be underestimated by as much as 36% if total nesting effort

is assumed to be constant from the first year of removal through the

third year (juvenile removal would not have a sudden impact on the

nesting segment of the population). Estimates of total nesting for 1984
and 1985 probably were underestimated because insufficient




















Table 1. Minimum total alligator nesting effort and removal rates on
Lakes Griffin, Jessup, Apopka, Woodruff and Paynes Prairie,
1981-1986.


























Q



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Figure 5. Maximum monthly water levels (NGVD) experienced on Lake
Griffin from October 1980-September 1986 (U. S. Geological
Survey, 1982-1986).













inr


NVPr-86


mnr


NYvP-t86


inr


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capture-recapture efforts resulted in underestimations of hidden nests.

Decreased nesting during low water (1984) probably resulted from

inaccessibility of traditional nesting locations and increased

physiological stress due to crowding and competition for food. However,

nesting attempts recovered in 1985 and 1986 (Table 1) and no decreasing

trends were found in juvenile size classes,indicating that short-term

negative impacts on the population was minimal.

Nesting estimates on Lake Jessup ranged from 74-129 during

1983-1986. Because canopy cover was absent in the major nesting areas

we feel confident that these estimates are accurate counts of actual

nesting effort. Variations in nesting from year-to-year likely can be

attributed to natural fluctuations in the proportions of breeding adult

females.

In years where reliable helicopter surveys were utilized to

estimate total nest production on Lake Apopka, average nesting effort

was 42 per year. A review of the 1981 data however, indicate that the

number of pods found increased when intensive hatchling removal efforts

were utilized. Although 81% of the estimated nests were found in this

manner during 1981, we could not assume that similar proportions of

nests were missed on successive years because of potential reproductive

failures. We do, however, recognize that total nesting estimates from

1983 1986 may be underestimated due to insufficient manpower to

implement capture-recapture efforts during that time.

Similarly, total nest production on control area Lake Woodruff

probably underestimated of actual nesting because of limited

capture-recapture efforts. These data, however, do likely represent

more reliable trend information because capture efforts were consistent








from year-to-year, unlike capture-recapture efforts on treatment areas.


Nest Depredation--Nest depredation varied among study areas as well

as among years within areas (Table 2). Variation among lakes likely was
the result of differing predator population densities and

behavior(principally racoons, Procyo Lotor), and accessibility of nests

to predators, whereas differences within lakes probably were related to

water level changes.

Yearly depredation rates were highest on Lake Woodruff (x= 33.5%,

sd = 14.0) and lowest on Lake Griffin (x = 12.3; sd = 5.7) (Table 2).
Rates averaged 17.0% (sd = 7.6) and 20.5% (sd = 7.5) for Lakes Jessup

and Apopka, respectively (Table 2). The highest depredation rates for

Lakes Griffin and Jessup occurred during low water periods of 1984 and

1986, respectively (Fig. 5, 6). Jennings et al. (1985) found that

alligator nest depredation patterns were clumped when water levels were

low, suggesting that low water levels increase marsh accessibility by

raccoons. In contrast, although Lake Woodruff experienced similar
hydrological fluctuations as Lake Jessup (Fig 6), depredation rates

appeared independent of water level.

Though speculative, these differences are best explained by

variations in available raccoon habitat, density and behavior. Cagle

(1949) proposed that certain populations of raccoons "learn" what foods

are available and then seek specific items. If certain raccoon
populations have thus "learned" when alligator nests are available and

selected for them, one might expect some wetland systems to suffer
higher rates of depredation. We know nothing of densities of raccoons

on any of the areas but suspect that even if habitats were similar













Table 2. Depredation rates of alligator nest on Lakes Griffin,
Jessup, Apopka, and Woodruff, from 1981-1986.




Year Number Nests Depredated Depredation Rate (%)

Lake Woodruff
1981 6 33
1982 3 11
1983 13 30
1984 14 33
1985 7 19
1986 27 52

Lake Griffin
1981 4 8
1982 -
1983 14 7
1984 26 21
1985 18 9
1986 23 12


Lake Jessup
1981 8 31
1982 -
1983 19 14
1984 24 19
1985 5 12
1986 46 23

Lake Apopka
1981 6 7
1982 -
1983 4 13
1984 9 22
1985 5 24
1986 12 23




















Maximum water levels (NGVD) experienced on Lake Jessup for
October 1980-September 1986 (U. S. Geological Survey,
1982-1986).


Figure 6.












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NVYr-t86L


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Nvr-126 i


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NVr-Z86L


inr


Nvr-1861


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River, size of the watershed, and geophysical variations. Clearly,

evaluation of the effects of these parameters on alligator nest success

will require additional and more precise information.

Flooding of alligator nests on Lake Apopka (R = 16.0%, sd = 14.9)

was not related to water level changes (Fig 7). These data, however,

must be interpreted carefully. Because flooding estimates were based

only on aerially observed nests, the potential existed to bias final

nest fate estimations based on subsamples. On Lake Apopka, this meant

that nests located in the relatively open (little canopy cover) marsh

community were more likely to be observed than nests located under the

heavy canopy cover of the bottomland hardwoods. Furthermore, we

expected nest flooding to be higher in the marsh habitat because nests

usually had poor substrate support and decomposed rapidly (pers. obs.).

Conversely, no flooded nests were located in the bottomland hardwood

association throughout this study. Comparison of habitat-specific nest

flooding (Table 4) clearly indicate that estimates of nest flooding

based on aerially observed nests overestimates total nest flooding

rates. Though this phenomenon may be unique to Lake Apopka, future

evaluation of nest flooding (and depredation) on other wetlands should

incorporate habitat specific monitoring where 2 or more distinct

habitats exist. The impact that flooding had on total nest success was

minimal on Lake Griffin, ranging from 2-11%.


Night-Light Counts

Analyses of night-light counts indicated no significant trends in

any of the size classes for alligators on Lake Woodruff (Fig. 9) or Lake

Griffin (Fig. 10, Table 5). As expected, none of the size class








productive areas in terms of alligator production. It is

likely that the majority of Florida wetlands are less

productive. Therefore, harvest levels for these areas-should

be set at more conservative levels until potential long term

impacts have been examined.


4. Ranching management programs should employ both hatchling and

egg removal. The decision of which technique to be employed

will depend upon the habitat, nesting density and

accessibility, and target rates.


5. Research efforts should be directed toward investigating egg

viability in major drainage basins of the state.

Specifically, comparisons of egg viability data may provide a

method of evaluating wetland quality and could potentially be

used as an early indicator of contaminant loading. Immediate

studies on the dramatic problems on Lake Apopka should be given

high priority.













Table 3. Flooding rates of alligator nests on Lakes Griffin,
Jessup, Apopka, and Woodruff, from 1981-1986.




Year Number Nests Flooded Flooding Rate(%)

Lake Woodruff
191 0 0
1982 0 0
1983 0 0
1984 3 7
1985 0 0
1986 1 2

Lake Griffin
1981 1 2
1982 -
1983 9 11
1984 1 2
1985 8 11
1986 0 0

Lake Jessup
1981 2 8
1982 17 100
1983 0 0
1984 30 60
1985 34 83
1986 7 5

Lake Apopka
1981 1 7
1982 -
1983 4 27
1984 0 0
1985 5 36
1986 3 10











Table 4. Comparison of alligator nest flooding rates in marsh'and
bottomland hardwood habitats on Lake Apopka from 1983-1985.


Hardwoods
number nests/flooded nests

12/0 (0%)

10/0 (0%)

23/0 (0%)


Marsh
number nests/flooded nests

29/4 (14%)

24/0 ( 0%)

23/5 (22%)


Year

1983

1984

1985








River, size of the watershed, and geophysical variations. Clearly,

evaluation of the effects of these parameters on alligator nest success

will require additional and more precise information.

Flooding of alligator nests on Lake Apopka (X = 16.0%, sd = 14.9)

was not related to water level changes (Fig 7). These data, however,

must be interpreted carefully. Because flooding estimates were based

only on aerially observed nests, the potential existed to bias final

nest fate estimations based on subsamples. On Lake Apopka, this meant

that nests located in the relatively open (little canopy cover) marsh

community were more likely to be observed than nests located under the

heavy canopy cover of the bottomland hardwoods. Furthermore, we

expected nest flooding to be higher in the marsh habitat because nests

usually had poor substrate support and decomposed rapidly (pers. obs.).

Conversely, no flooded nests were located in the bottomland hardwood

association throughout this study. Comparison of habitat-specific nest

flooding (Table 4) clearly indicate that estimates of nest flooding

based on aerially observed nests overestimates total nest flooding

rates. Though this phenomenon may be unique to Lake Apopka, future

evaluation of nest flooding (and depredation) on other wetlands should

incorporate habitat specific monitoring where 2 or more distinct

habitats exist. The impact that flooding had on total nest success was

minimal on Lake Griffin, ranging from 2-11%.


Night-Light Counts
Analyses of night-light counts indicated no significant trends in

any of the size classes for alligators on Lake Woodruff (Fig. 9) or Lake

Griffin (Fig. 10, Table 5). As expected, none of the size class




















Maximum water levels (NGVD) experienced on Lake Apopka from
October 1980-September 1986 (U. S. Geological Survey,
1982-1986).


Figure 7.




























L w


<
LLJ t















II

co ON ) 1
(0 (D
(cIAON) 73A3A


co In
(0
I31VM XVVN


inp


NVP-g861


inr


NVPr-*86


Inr


NVP-86L


in-


NVP-Z861


inr


NVP-L9866



















Figure 9. Alligator population trends on Lake Woodruff based on
night-light surveys conducted from 1981-1986.




L.MY\n. -vv Un.uLJrr
(2-4 Ft. Size Classes)


1981 1982 1983 1984 1985 1986


LAKE WOODRUFF
(2-6 Ft. Size Classes)


1981 1982 1983 1984 1985 1986


LAKE WOODRUFF
(>'2 Ft. Size Classes)


1982 1983 1984 1985
Year


250-



200

ID


0



* 100
150
*


-- Adj. Counts
-0- Est. Trend


*-- Adj. Counts
--l Est. Trend


V250:

c
o 200'
U




< 100,


50


--- Adj. Counts
-8- ELt Trend




















Figure 10.


Alligator population trends on Lake Griffin based on
night-light surveys conducted from 1981-1986.




LAKE GRIFFIN
(2-4 Ft. Size Closses)


Year


LAKE GRIFFIN
(2-6 Ft. Size Classes)


-+- Adj. Counts
-- Est. Trend


LAKE GRIFFIN
(>2 Ft Size Classes)


-4- Adj. Counts
- Est. Trend


-+- Adj. Counts
-8- Est. Trend


3180--
1980


1100'






3 900
l00.


o
, oo.



=700


G00.


Year


1988

















Table 5. Analyses of night-light survey data for evaluation of
trends in the 2-4, 2-6, and 2 feet size classes on
Lakes Griffin, Jessup, Apopka, and Woodruff, from
1980(1)-1986.


2-4 feet
t(P)


Lake


2-6 feet
t(P)


2 feet
t(P)


Lake Griffin 0.349(0.7376) 0.062(0.9524) 0.556(0.5955)
Lake Apopka -5.182(0.008) -6.078(0.0003) -5.913(0.0004)

Lake Jessup 1.519(0.1725) 2.152(0.0684) 3.090(0.0176)
Lake Woodruff 1.663(0.1403) 1.733(0.1267) 1.665(0.1400)








categories were affected on our non-harvested control area. Stable

population numbers on Lake Griffin suggested that recruitment into the

2-6 foot size classes remained constant. Trends on Lake Jessup

indicated significant increases in animals>2 feet (Fig.11). Analyses of

trends for animals in the 2-4 and 2-6 ft. size classes indicated only

slight increases (Table 5), suggesting the overall population increase

probably was attributed to increases in the numbers of alligators>6

feet. Although animals larger than 6 feet probably have not directly

been affected by the removal treatment (eg. they do not belong to

cohorts hatching after 1981) their increase is difficult to explain.

Because the number of animals in the 2-6 ft size classes increased only

slightly over the past 6 years it is unlikely that the observed increase

in alligators>6 feet is to be a function of animals maturing and

entering the larger size classes. More likely, large alligators were

emigrating from Lake Monroe to Lake Jessup via the St. John's River.

Poaching also may have resulted in a larger scale movement of animals

than would be expected naturally. If poaching was an important source

of adult mortality, then the movement of new animals into those empty

territories may have resulted in a net increase in large alligators.

Alternatively, if the number of large alligators (>6ft) had been reduced

by poaching it is possible that higher survival was experienced by those

animals just approaching maturity because of reduced competition from

mature animals.
Analyses of trend data for Lake Apopka indicate significant

decreases in population numbers (Fig 12, Table 5). That decreases were

identified in all size classes (including> 6 ft) indicates that the

removal treatment was not responsible for the observed population

declines.




















Figure 11. Alligator population trends on Lake Jessup based on
night-light surveys conducted from 1981-1986.




(2-4 Ft. Size Classes)


-- Adj. Counts
--- Est. Trend


1983 1984 1985 1986


LAKE JESSUP
(2-6 Ft. Size Closses)


-- Adj. Counts
--- Est. Trnd


1981 1982 1983 1984 19815 I9g
Yeor


SLAKE JESSUP
(>2 Ft. Size Closses)


- Adj. Counts
-e- Est. Trend


1982 1983 1984


o00

o
3001


S200


100
100


1981


'V

- 500-
o
U -
so
0
4
"o 00 r
.0'
a


300-


V

S6o00
0
o
u




















Figure 12.


Alligator population trends on Lake Apopka based on
night-light surveys conducted from 1980-1986.




LAKE APOPKA
(2-4 Ft. Size Classes)


1981 1082 1983
Year


1984 1985 1988


LAKE APOPKA
(2-6 Ft. Size Classes)


80 1981 1982 1083
Year


1984 1985 19I


LAKE APOPKA
(>2 Ft. Size Classes)


- Adj. Count*
-e- Et. Trend



















6







-- Adj. Counts
-- Est. Trend


1980 1981 1982 1983
Year


1984 1985 Io8


-- Adj. Counts
- E- Est. Trend


1000-
r -



8001




0
Uo

0
" 400-



200-


O"









1200


1000


c
boo

0
,.)
O
-600


400







Cost-Benefit Ratio of Collecting Wild Production

The relative cost per collected hatchling in 1982 was $11.45 on

Lake Griffin and $21.97 on Lake Apopka (Table 6). Egg collection costs

per viable hatchling during 1985 were $3.34, $9.96, and $15.80 on Lakes

Griffin, Jessup, and Apopka, respectively (Table 7).

Difference in hatchling costs between Lakes Griffin and Apopka

likely was the result of lake size, habitat accessibility, and total

nest production. Lake Apopka is approximately 3 times as large as Lake
Griffin and produced only 1/3 as many nests over a much broader area,

resulting in a proportionately greater search effort and thus a greater

cost per hatchling. Further, pod locations often were in inaccessible

areas which required numerous revisits to completely remove the entire

pod. Although pod locations were generally accessible on Lake Griffin,

high water levels often precluded total capture of an entire pod.

It became evident that in systems with relatively dense nesting (e.g.

Griffin) collection efficiency could be maximized by collecting

hatchlings from pods that were most accessible while leaving those that

remained deep in the marsh.

Although hatchling costs derived from egg collection techniques

were lower on all lakes than costs from hatchling collection, there were

large differences among lakes. These differences primarily were due to

differential nesting densities, nest site accessibility, nest

observability and egg hatchability. On Lake Griffin, where nesting

rates were high and dense and located within 50 m of the shoreline,

efficient use of aircraft and ground crews resulted in the lowest costs

per hatchling. Further, habitat type (thus nest observability) also

influenced the cost of egg removal. For example, aerial surveys are




















Table 6. Estimated costs of hatchlings derived from the collection of
juvenile alligators, on Lakes Griffin and Apopka during 1982.









COST OF HATCHLING COLLECTION (1982)


LAKE GRIFFIN
Personnel
search time
travel time
planning

Travel
Gasoline (autos)

Airboats
Misc. equip.
(wheatlights, tongs, tags)


398 hrs @ 6.00/hr
71 hrs @ 6.00/hr
100 hrs/3 lakes @
10.00/hr

70 days @ 50.00/hr

104 hrs @ 22.00/hr


Total cost


Total cost/hatchling ($9810.00/857)


LAKE APOPKA
Personnel
search time
travel time
planning

Travel
Gasoline (autos)

Airboats
Misc. equip.
(wheatlights, tong, tags)


32 hrs @ 6.00/hr
12 hrs @ 6.00/hr
100 hrs/3 lakes @
10.00/hr

8 days @ 50.00/day

16 hrs @ 22.00/hr


Total/cost


$1824.00


Total cost/hatchling ($1824.00/83)


2388.00
426.00

333.00

3500.00
500.00

2288.00
375.00

$9810.00


$11.45


192.00
72.00

333.00

400.00
100.00

352.00
375.00


$9810.00


$21.97




















Table 7. Estimated costs of hatchling alligators derived from egg
collections, on Lakes Griffin ,Jessup, and Apopka during 1986.







COST OF EGG COLLECTION (1986)


LAKE GRIFFIN
Personnel
air time
ground crews
travel time
planning

Travel
Gasoline(autos)

Helicopter

Airboats
Misc. equip.


16.9 hrs @ 6.00/hr
127.5 hrs @ 6.00/hr
36 hrs @ 6.00/hr
33.3 hrs @ 10.00/hr

9 people X 4 days @ 50.00/day

16.9 hrs @ 125.00/hr

5 boats 13.5 hrs @ 25.00/hr


Total cost
Total cost/hatchling ($6468.40/1936)


LAKE JESSUP
Personnel
air time
ground crew
travel time
planning


Travel


Helicopter

Airboats
Misc. equip.


10.3 hrs
90 hrs @
36 hrs @
33.3 hrs


@ 6.00/hr
6.00/hr
6.00/hr
@ 10.00/hr


9 people X 4 days @ 50.00/day

10.3 hrs @ 125.00/hr

5 boats 9.0 hrs @ 25.00/hr


Total cost
Total cost/hatchling ($5696.30/572)


LAKE APOPKA
Personnel
airtime
ground crews
travel time
planning


Travel


Helicopter

Airboats
Misc. equip.


2.5 hrs @ 6.00/hr
48 hrs @ 6.00/hr
16 hrs @ 6.00/hr
33.3 hrs @ 10.00/hr


8 people x 4 days @ 50.00 day

2.5 hrs @ 125/hr

4 boats 6 hrs @ 25.00/hr


Total cost
Total cost/hatchling ($3777.00/239)


101.40
765.00
216.00
333.00

1800.00
120.00

2112.50

1687.50
333.00

$6468.40
$ 3.34


61.86
540.00
216.00
333.00

1800.00

1287.50

1125.00
333.00

$5696.30
-- 9.96


15.00
288.00
96.00
333.00

1800.00

312.50

600.00
333.00

$3777.00
$ 5.80







inefficient along wooded shorelines such as on Lake Apopka.

Approximately one-half of the estimated production was aerially observed

on a small remnant marsh bordering the north shore. Of these nests,

only 25-50% were accessible by ground crews in any given year. The

remaining production occurred on the western and southern shores in

bottomland hardwood associations. Nests were difficult to observe from

the air due to the thick canopy and less efficient ground searches were

initiated to locate nests.

More importantly, egg hatchability was very critical in

determining final cost per viable hatchling. Artificially incubated

Lake Griffin eggs had a mean hatching rate of 68.0%, much higher than

Lakes Jessup (42.5%) or Apopka (23.5%). Thus, more hatchlings per unit

effort results from collections on Lake Griffin than on Lakes Jessup or

Apopka.

Finally, initial capital expenditures for organizational planning

(approximately $1,000) and miscellaneous equipment ($1,000) represented
7.2% and 38.9% of total hatchling costs for juvenile removal on Lakes

Griffin and Apopka, respectively. Similar costs involved in egg removal

efforts represented 10.2% (Lake Griffin), 48.1% (Lake Apopka), and 11.6%

(Lake Jessup) of the total cost per hatchling. Due to the experimental

nature of this project these costs probably reflect a larger portion of

the actual costs per hatchling than would be expected with operational

harvest programs. Though the actual costs likely would be lower, the

facts remain that costs would vary with factors such as nest density,

accessibility, and hatchability.







Nesting Parameters
Artificial incubation of wild alligator eggs provided an

opportunity to compare clutch size, fertility and hatchability rates

among central Florida lakes (Woodward 1985). Although this information

was not initially considered imperative to the evaluation of prescribed

removal rates it has ultimately provided valuable information on
potential reproductive failures on Lake Apopka as well as early warnings

of reproductive problems on Lake Jessup.

From 1984 1986 total clutch size on Lake Apopka ranged from

44.8 46.3 (Tf= 45.3) and was not significantly different (P > 0.05)
than Lakes Griffin (x = 45.4) or Jessup (X = 45.8). Hatching rates,

however, ranged from 20.0%-25.0%, and were significantly lower (P = <

0.05) than Lakes Griffin (66.6% 70.3%) and Jessup (38.0% 69.0%).

Interestingly, an average of only 5.8, 8.5, and 5.8 alligators

successfully hatched from each Apopka nest containing fertile eggs
during those years, even though fertility rates (72.0-74.0) were not

significantly different (P> 0.05) than Lakes Griffin and Jessup.

Additionally 35.0%, 15.2%, and 13.0% of all visited nests contained only
infertile eggs from 1984 1986, respectively. These data strongly

suggest that declining population densities on Lake Apopka are due to
reproductive failures and developmental problems and not removal levels.

A convenient explanation for these reproductive failures would

center around the possibility of a large influx of environmental
contaminants entering the system via insecticide spraying of orange

groves and vegetable farms. Preliminary results of alligator eggs
analyzed at the Patuxent Wildlife Research Center of the U.S. Fish and
Wildlife Service indicate that p,p'-DDE, p,p'-DDD, and dieldrin were








consistently found in all eggs and cis-Chloradane, trans-Nonachlor,

cis-Nonachlor, toxaphene, and PCB were found in some, but not all eggs

(Table 8). Ogden et al. (1973) and Hall et al. (1979) found many of the
same organochlorines in the eggs of American crocodiles in south

Florida, but did not speculate on the impact on crocodilian reproductive

success. The levels of most organochlorines reported in the latter two

studies were much lower than levels reported here. Specifically, Ogden

et al. (1973) and Hall et al. (1979) reported average DDE and Dieldrin
levels of 1.84 and 1.19 and 0.01 and 0.02 ppm respectively.

DDE levels in Lake Apopka eggs (T6= 6.1 ppm) were significantly

higher (P< 0.05) than levels in Lake Griffin (x = 0.82 ppm) and Lake

Okeechobee (x = 1.2 ppm). These elevated DDE levels were high enough to

cause reproductive failures in the most sensitive avian species (Hickley

and Anderson 1968, Blus et al. 1974). Levels of all other

organochlorines did not appear to be high enough to cause reproductive

problems in alligators based on the literature for birds (G. Heinz pers.

comm.). No differences were detected in thickness or shell quality of

alligator eggs among lakes. Although these results are inconclusive

and based on rather small sample sizes, there is sufficient evidence to

warrant substantial research effort on the effects of organachlorine

contamination on alligator reproduction in Lake Apopka.

Additional hypotheses developed to explain the poor reproductive

success of alligators on Lake Apopka include population demographics and

stress. It has been suggested that the majority of the reproductive
segment may be approaching senescence and are therefore incapable of

producing viable clutches. This argument, however, does not explain why
the number of juvenile alligators (>6 ft.) continues to decline.




















Table 8. Results of analysis for presence of 12 organochlorines (ppm)
in 6 alligator eggs taken from Lake Apopka during 1984.
















SAMPLE NUMBER

Compound 1 2 3 4 5 6

p,p'-DDE 8.1 7.2 7.1 7.6 3.7 3.2

p,p'-DDD 0.96 0.56 1.0 0.99 0.80 0.66

p,p'-DDT -
Dieldrin 0.30 0.27 0.48 0.57 0.11 0.09

Hept. epoxide -

Oxychlordane -

cis-Chlordane 0.14 0.12 0.09 0.08

trans-Nonachlor 0.16 0.11 0.20 0.09

cis-Nonachlor 0.13 0.09 -

Endrin -

Est. Toxaphene 0.11 0.14 0.12 -

Est. PCB 0.36 0.84 -


-not detected







Alternatively, stress, related to food availability and quality, also

has been considered as a limiting factor in reproductive success and

juvenile survival. Unfortunately, no comprehensive and consistent data

are available for evaluating fluctuations in prey base populations.


Conclusion

The removal of 50% annual alligator production over a 6 year period

on 3 central Florida lakes did not significantly decrease population

size structures. On Lake Jessup significant increases were found in the

2+ ft. size classes, while on Lake Griffin no significant changes were

found in any size classes. Lake Apopka experienced significant

(P < 0.05)declines in all size classes, but this phenomenon is more

likely due to currently unexplained reproductive failures and not the

early age-class harvest. No significant change (P > 0.05) in size

structure was found for the control area, Lake Woodruff.

Cost-benefit ratios for the hatchling egg collections varied

between techniques and among lakes. Hatchling removal is most efficient

in wetland systems with dense nesting effort and distinct water-marsh

interfaces. Similarly, egg collections are most efficient in wetland

areas containing dense nesting concentrations and in areas with

indiscrete water-marsh interfaces. A monetary comparison of both

techniques indicate that egg collection is most efficient when large

proportions of a population are to be managed. When very conservative
limited removal rates are prescribed, however, hatchling collection

becomes more cost effective because of the high start-up costs of egg

collection. For example, if a quota of 100 hatchlings (as opposed to 25

clutches of eggs) were set for a given system, it would be much more







efficient to simply allow a trapper to remove them.

The biological impacts of hatchling and egg removal appear

equivalent. Although hatchling removal allows natural mortality of

nests and hatchlings to act upon production, egg removal obviates this

mortality and results in a greater number of animals collected.

An effect of habitat type on nest success was not demonstrated.

Low water levels during nest incubation, however, did precipitate higher

depredation rates by raccoons in specific habitat locales (Jennings

1986.)

Juvenile growth and survival rate estimates could not statistically

be analyzed due to insufficient recapture data. Growth rate models will

be pursued when additional recapture data are available. Survival rate

estimation for the American alligator is probably impractical because of

sample size requirements.









Recommendations


The objective of this research project was to evaluate the impacts

of removal on alligator populations. Although we were unable to fully

address all facets, the data gained provided sufficient information to

identify the short term responses of alligator populations to a 50%

removal of annual production. Based on these findings and the questions

stimulated by this investigation the following recommendations are

suggested.


1. A 50% removal treatment should continue on all 3 study areas

for at least an additional 5 years. Long-term trends in

alligator populations cannot adequately be evaluated during a

one 5-year study, and any lapse in treatment may confound

interpretation of future demographic impacts.


2. Additional monitoring, including nest surveys, night-light

surveys and capture-recapture efforts, should continue on all

study areas. These data will add to baseline information

already available on growth rates. Further, such

monitoring also will provide a mechanism to ensure that any

long term impacts are detected and quantified.


3. That 50% annual removal has had no apparent negative impact on

3 central Florida lakes does not imply that 50% removal rates

can be sustained on all Florida wetlands. In contrast, the

3 treatment lakes now under study represent several of the most









productive areas in terms of alligator production. It is

likely that the majority of Florida wetlands are less

productive. Therefore, harvest levels for these areas should

be set at more conservative levels until potential long term

impacts have been examined.


4. Ranching management programs should employ both hatchling and

egg removal. The decision of which technique to be employed

will depend upon the habitat, nesting density and

accessibility, and target rates.


5. Research efforts should be directed toward investigating egg

viability in major drainage basins of the state.

Specifically, comparisons of egg viability data may provide a

method of evaluating wetland quality and could potentially be

used as an early indicator of contaminant loading. Immediate

studies on the dramatic problems on Lake Apopka should be given

high priority.









Literature Cited


Blus, L. J., B. S. Neely, Jr., A. A. Belisle, and R. M. Prouty. 1974.

Organochlorine residues in Brown Pelican eggs: relation to

reproductive success. Environ. Pollut. 7:81-91.


Cagle, F.R. 1949. Notes on the raccoon, Procyon lotor megalodus Lowery.

J. Mammal. 30:45-47


Campbell, H.W. 1972. Ecological or phylogenetic interpretations of

crocodilian nesting habits. Nature 238:404-405.


Canfield, D.E., Jr. 1981. Chemical and trophic state characteristics

of Florida Lakes in relation to regional geology. Sch. For. Res.

and Cons., Univ. of FL., Gainesville. 444 pp (Mimeo).


Deitz, D.C., and T.C. Hines. 1980. Alligator nesting in north-central

Florida. Copeia 1980:249-258.


Ferguson, M.W.J. 1981. Extrinsic microbial degradation of the

Alligator eggshell. Science 214:1135-1137


Hall, R. J., T. E. Kaiser, W. B. Robertson, Jr., and P. C. Patty. 1979.

Organochlorine residues in eggs of the endangered American

Crocodile (Crocodylus acutus). Bull Environ. Contam. Toxicol.

23:87-90.









Hickey, J. J. and D. W. Anderson. 1968. Chlorinated hydorocarbons and

eggshell changes in raptorial and fish-eating birds. Science.

162:271-273.


Hines, T.C. 1979. The past and present status of the alligator in

Florida. Proc. Ann. Conf. S.E. Assoc. Game and Fish Comm.

33:224-232.


Jacobsen, T., and J.A. Kushlan. 1986. Alligator nest flooding in the

southern Everglades: A methodology for management. Pages 153-174

in Proc. 7th working meeting I.U.C.N. Crocodile specialists Group,

Caracas, Venezuela. 446 pp.


Jennings, M.L., H.F. Percival and C.L. Abercrombie. 1986. Habitat

variables and spacing patterns affecting the nesting success of the

American alligator in central Florida. M.S. Thesis. Univ. of FL,

Gainesville. 33 pp.


Joanen, T. 1969. Nesting ecology of alligators in Louisiana. Proc.

Ann. Conf. S. E. Assoc. Game and Fish Comm. 23:141-151.


Johnson, D. H. 1979. Estimating nest success: the Mayfield method and

an alternative. Auk 96:651-661.


National Res. Council. 1983. Crocodiles as a resource for the tropics.

National Academy Press, Washington D.C. 59 pp.









Ogden, J. D., W. B. Robertson, Jr., G. E. Davis, and T. W. Schmidt.

1974. Pesticides, polychlorinated biphenols and heavy metals in

upper food chain levels, Everglades National Park and vicinity.

National Park Service Management Report. 27pp.


Rose, M. 1982. Crocodile management and husbandry in Papua New Guinea.

Pages 148-163 in Proc. 6th working meeting I.U.C.N. Crocodile

specialists Group, Victoria Falls, Zimbabwe. 219 pp.


Wood, J.M., A.R. Woodward, S.R. Humphrey, and T.C. Hines. 1985. Night

counts as an index of American alligator population trends. Wildl.

Soc. Bull. 13:262-272.


Woodward, A.R. 1985. (in press) Time of collection of wild alligator

eggs in Florida for ranching. in Proc. Fourth Annual Alligator

Production Conf. Gainesville, Florida.


Woodward, A.R. and W.R. Marion. 1978. An evaluation of factors

affecting night-light counts of alligators. Proc. Ann. Conf.

Southeast. Assoc. Fish and Wildl. Agencies. 32:291-302.




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