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2007 SOUTHEASTERN NATURALIST 6(1):97–110
Alligator Diet in Relation to Alligator Mortality on
Lake Griffin, FL
Amanda N. Rice1,2,*, J. Perran Ross3, Allan R. Woodward4,
Dwayne A. Carbonneau5, and H. Franklin Percival6
Abstract - Alligator mississippiensis (American Alligators) demonstrated low hatchrate
success and increased adult mortality on Lake Griffin, FL, between 1998 and
2003. Dying Lake Griffin alligators with symptoms of poor motor coordination were
reported to show specific neurological impairment and brain lesions. Similar lesions
were documented in salmonines that consumed clupeids with high thiaminase levels.
Therefore, we investigated the diet of Lake Griffin alligators and compared it with
alligator diets from two lakes that exhibited relatively low levels of unexplained
alligator mortality to see if consumption of Dorosoma cepedianum (gizzard shad)
could be correlated with patterns of mortality. Shad in both lakes Griffin and Apopka
had high levels of thiaminase and Lake Apopka alligators were consuming greater
amounts of shad relative to Lake Griffin without showing mortality rates similar to
Lake Griffin alligators. Therefore, a relationship between shad consumption alone
and alligator mortality is not supported.
Alligator mississippiensis Daudin (American Alligators) have been affected
by unknown factors on Lake Griffin, FL, causing low hatch-rate
success and adult mortality (Ross et al. 2003, Schoeb et al. 2002). Alligator
egg hatch-rate success dropped to 10% between 1994 and 1997 (A.R. Woodward,
unpubl. data). Between November 1998 and December 2003, researchers
recorded 439 dead alligators on Lake Griffin, of which approximately
98% were adults (D.A. Carbonneau, unpubl. data, (Fig. 1). Most
alligator deaths occurred in spring, and over 100 individuals died that season
in some years; however, alligator deaths were recorded all months of the
year during bi-weekly surveys.
Between 1998 and 2003, we observed Lake Griffin alligators that were
lethargic, unresponsive to human approach, and had uncoordinated
behavior. Subsequently, these alligators may have died of drowning.
Pathology examinations have shown that these Lake Griffin alligators were
1Florida Museum of Natural History, Box 117800, University of Florida, Gainesville,
FL 32611. 2Current address - Florida Fish and Wildlife Conservation Commission,
7922 NW 71st Street, Gainesville, FL 32653. 3Department of Wildlife Ecology and
Conservation, Newins-Ziegler Hall, Box 110430, University of Florida, Gainesville,
FL 32611. 4Florida Fish and Wildlife Conservation Commission, 4005 South Main
Street, Gainesville, FL 32601. 5Florida Fish and Wildlife Conservation Commission,
1239 SW 10th Street, Ocala, FL 34474. 6US Geological Survey, Florida Cooperative
Fish and Wildlife Research Unit, University of Florida, PO Box 110485, Gainesville,
FL 32611. *Corresponding author - Amanda.Waddle@MyFWC.com.
98 Southeastern Naturalist Vol. 6, No. 1
affected by severe neurological impairment of unknown causes (Schoeb et
al. 2002). These included reduced nerve conduction velocity, degeneration
of nerves and characteristic lesions of the torus semicircularis in the midbrain.
Organochlorine and organophosphate pesticides, heavy metals, West
Nile virus, botulism, and infectious diseases were all investigated and
rejected as being associated with this mortality event (Ross et al. 2002).
Similar legions and patterns of hatchling mortality and adult impairment as
observed in Lake Griffin alligators have been seen in Great Lake
salmonines that resulted from thiamin deficiency (Honeyfield et al. 2005).
Because of this similarity in pathology, thiamin levels of Lake Griffin
alligators were analyzed in 1999 and 2000. Thiamin levels in Lake
Woodruff alligators also were analyzed as a reference representing
unimpaired alligators. Lake Griffin alligators had lower thiamin levels than
Lake Woodruff alligators and seriously impaired Lake Griffin alligators
had lower thiamin levels than less seriously impaired specimens (Ross et
The cause of neurological impairment in salmonines was the abundance
of prey rich in thiaminase, including Alosa psuedoharengus Wilson (Alewife),
Osmerus mordax Mitchill (Rainbow Smelt), and Clupea harengus
membras Linnaeus (Baltic Herring), which are all filter feeders (Tillitt et al.
2005). American Alligators are known to prey on fish throughout their range
in Florida (Delany and Abercrombie 1986; Delany et al. 1988, 1999; Rice
2004). Dorosoma cepedianum Lesueur (Gizzard Shad), an abundant clupeid
filter feeder, was available to alligators in many central Florida lakes.
Because Lake Griffin alligators showed similar symptoms to salmonines—
low tissue thiamin levels, reproductive failure, adult neural impairment, and
Figure 1. Annual alligator mortality in Lake Griffin, FL during 1998–2003, based on
2007 A.N. Rice, J.P. Ross, A.R. Woodward, D.A. Carbonneau, and H.F. Percival 99
brain lesions (Honeyfield et al. 2005, Schoeb et al. 2002)—and had access to
similar prey fish types, we investigated alligator diets in Lake Griffin and
nearby Lakes Apopka and Woodruff, where alligators did not demonstrate
these characteristics. We hypothesized that elevated alligator mortality on
Lake Griffin was due to a diet high in D. cepedianum with high levels of
thiaminase causing a depressed level of thiamin in alligators.
Body condition analyses investigate an animal’s energy store compared
to its body size and are affected by abiotic and biotic components in their
habitat (Green 2001). Delany et al. (1999) found differences in alligator
condition among lakes in Florida and found that a high condition correlated
with a fish-dominated diet. Because condition analyses indicate health of a
population (Sutton et al. 2000) and it is unknown if thiamin deficiency
affects alligator condition, we examined Lake Griffin alligator condition and
compared it to alligator condition from Lakes Apopka and Woodruff.
The study was conducted in Lake Griffin (Lake County—28º50'N,
81º51'W), Lake Apopka (Lake and Orange counties—28º37’N, 81º37'W),
and Lake Woodruff National Wildlife Refuge (Volusia County—29º06'N,
81º25'W). Neither Lake Apopka nor Lake Woodruff were having unusual
adult alligator mortality events and were chosen as comparative study lakes
because of their lake characteristics. Lake Apopka has similar lake characteristics
to Lake Griffin, and Lake Woodruff is a cleaner, more pristine lake
for comparison. Lakes Griffin and Apopka are hypereutrophic, alkaline,
polymictic, shallow water bodies and are a part of the Ocklawaha chain of
lakes (Rice 2004). Throughout much of the early 1900s, both lakes were
clear, macrophyte-dominated lakes; however, in the mid-1900s, both lakes
dramatically changed due to water-level controls, diking and draining associated
marshes, urban runoff, sewage, and agricultural effluents, resulting in
eutrophication (Canfield et al. 2000, Woodward et al. 1993) as well as
pesticide pollution (Heinz et al. 1991). Since the late 1990s, both lakes
experienced restoration efforts to improve water quality. These efforts included
planting native vegetation, fish removal to reduce phosphorus levels,
restoration of marsh on surrounding muck farms, and implementation of a
marsh flow-way system to filter the water (Fernald and Purdum 1998). Lake
Woodruff National Wildlife Refuge, along the St. Johns River, is a macrophyte-
dominated, eutrophic, alkaline lake (Rice 2004). Lake Woodruff has
experienced little agriculture and urban development, and its alligator population
had consistently high hatching rates (A.R. Woodward, unpubl. data)
and low levels of adult mortality.
During 2001–2003, we captured adult alligators by capture dart and
snare from airboats between 2000 and 0400 hours. Each alligator was
100 Southeastern Naturalist Vol. 6, No. 1
marked with two Monel self-piercing tags (National Band and Tag Co.,
Newport, KY), sexed by manual palpation, and weighed to the nearest 2 kg
using a spring scale. Standard measurements including total length (TL),
snout vent length (SVL), tail girth (TG), and head length (HL) were taken
with a flexible tape to the nearest 0.1 cm.
Stomach contents were obtained predominantly from live adult alligators
within 3 hours of capture using the stomach pumping “hose-Heimlich”
technique described by Fitzgerald (1989) and modified by Rice et al. (2005).
This technique reliably recovered most of the stomach content and allowed
subsequent release of the alligator unharmed. Additional stomach samples
were obtained during necropsy of alligators by other researchers.
Stomach-content samples were washed with water through a 0.5-mm
nylon mesh strainer, preserved in 70% ethanol, and stored in the laboratory.
Samples were sorted by prey group (fish, reptiles, mammals, birds, amphibians,
gastropods, insects, crustaceans, or bivalves) and non-prey items. Prey
items were then identified to the lowest possible taxa and minimum numbers
of individuals by comparing to reference specimens and skeletons in the
collection of the Florida Museum of Natural History (FLMNH).
All prey items were categorized as either freshly ingested (fresh) or not
freshly ingested (old) to avoid over-representation of indigestible prey. Alligators
are unable to digest chitin and keratin (Garnett 1985, Magnusson et al.
1987) and persistent animal parts such as hair, feathers, scutes, and snail
opercula may be overrepresented and bias quantitative estimates of prey
intake. Guidelines were established based on available literature to categorize
each prey item as either fresh or old (Barr 1994, 1997; Delany and
Abercrombie 1986; Janes and Gutzke 2002). The time range for prey to be
categorized as fresh varied with each prey taxa, but ranged between 24 and 72
hours (Rice 2004). Only freshly ingested material was considered in this
analysis. Live mass of fresh prey was estimated by allometric scaling (Brown
and West 2000, Casteel 1974, Reitz et al. 1987), field data, and available
published weight data for different groups (Burt and Grossenheider 1980,
Dunning 1993, Hoyer and Canfield 1994). Fresh invertebrates (except for
Gastropods) were weighed to the nearest 0.01 g.
Frequency of occurrence (percent of stomach samples containing a given
prey type) and percent composition by live mass (percent of the diet each
prey group or taxa represents based on estimated live-prey mass) were used
to quantitatively analyze the fresh-diet data. The Kruskal-Wallis analysis of
variance rank test was used to compare mean fish proportion in alligator
diets among lakes, and when significant differences were found, the lakes
were compared pair-wise using the Mann-Whitney U test.
Fulton’s condition factor (K = W/L3 * 10n, where W = mass of the
alligator in kg, L = SVL in cm, and n = 5), was used to determine each
alligators condition (Zweig 2003). Condition data were analyzed using a
general linear model with the least significant difference (LSD) post-hoc
2007 A.N. Rice, J.P. Ross, A.R. Woodward, D.A. Carbonneau, and H.F. Percival 101
test. Values for both diet and condition data were expressed as the mean ±
one standard error unless otherwise indicated. All statistical analyses were
performed using SPSS software (SPSS 2000). Both diet and condition statistical
tests used an alpha of 0.10, with the null hypothesis of no differences.
All analyses were performed on samples combined for all three years
and then compared among the three lakes. However, Lake Griffin
samples were quantitatively analyzed each year to compare the shad consumption
year to year. Impaired Lake Griffin alligators were sampled
along with normal Lake Griffin alligators during 2001. These samples
were analyzed in the same manner as the other samples; however, these
analyses were kept separate from normal Lake Griffin samples. No statistical
analyses were performed on these samples due to small sample size.
Results and discussion pertain to samples from normal (unimpaired) alligators
among the lakes, unless indicated by stating that they were
samples from impaired alligators.
Stomach contents from 175 normal American Alligators ranging in size
from 182 cm to 304 cm TL were collected from alligators captured at Lakes
Griffin (n = 85), Apopka (n = 44), and Woodruff (n = 46) from March to
October 2001, from April to October 2002, and from April to August 2003.
Stomach contents from an additional 13 alligators were collected from
impaired Lake Griffin alligators post-mortem during 2001 (Schoeb et al.
2002). The alligators ate a wide variety of vertebrate and invertebrate prey.
Fish were the most important prey group in frequency of occurrence and
percent composition by live mass for all lakes. Alligators from Lake Apopka
had the highest occurrence of fresh fish (64%), followed by Lake Woodruff
(57%) and Lake Griffin (44%) (Table 1). Fish made up an overwhelming
percentage of the mass of alligator stomach samples from Lakes Apopka
(90% of the diet) and Woodruff (80% of the diet). Total fish biomass for
Lake Griffin alligators was 54% of the diet (Appendix 1). While fish were
the predominant prey in all lakes, species composition and number of fish
Table 1. Percent occurrence of fresh prey in alligator stomachs collected from Lakes Apopka,
Griffin, and Woodruff, FL during 2001–2003.
Griffin (n = 85) Apopka (n = 44) Woodruff (n = 46)
% occurrence % occurrence % occurrence
Fish 44 64 57
Reptile 14 7 2
Mammal 2 5 2
Bird 5 2 0
Amphibian 6 0 4
Gastropod 28 9 41
Bivalve 4 0 4
Crustacean 9 11 15
Insect 8 9 13
102 Southeastern Naturalist Vol. 6, No. 1
consumed varied among lakes. Catfish (Ictaluridae) were most commonly
consumed in Lake Griffin, shad (Clupeidae) in Lake Apopka, and sunfish
and bass (Centrarchidae) in Lake Woodruff (Appendix 1).
Proportion of fish (by estimated fresh biomass) in individual alligator
stomachs ranged from 0 to 100%. Lake Apopka alligators had the highest
mean proportion of fish in their diet (mean = 79.9% ± 6.76), followed by
Lake Woodruff (mean = 59.4% ± 7.5) and Lake Griffin (mean = 48.5% ±
6.05) (Fig. 2). Proportion of fish in alligator stomachs differed among lake
(P = 0.006), and proportion of fish in alligator stomachs from Lake Apopka
was greater than those from Lakes Griffin (P = 0.002) and Woodruff (P =
0.018). Proportions of fish in Lakes Griffin and Woodruff alligator stomachs
were not significantly different (P = 0.403).
The predominant prey group consumed by Lake Griffin alligators each
year was fish, ranging from 43–68% of the diet (Table 2). Fresh shad (D.
cepedianum and Dorosoma spp.) represented 38% of the diet of samples
from Lake Griffin in 2001, making Clupideidae he predominant family of
fish consumed that year. However, no shad were identified in any 2002
samples, and a single old shad was identified in one sample in 2003 (Table 2)
(and catfish (Ictaluridae) were the predominant family of fish consumed by
Lake Griffin alligators that year (Table 3).)
Other vertebrate prey groups (reptiles, mammals, birds, and amphibians)
and invertebrates were found less frequently in alligator stomachs in all the
lakes (Table 1), and reptiles were the most commonly consumed vertebrate
prey after fish. Turtles were the most common reptiles consumed by the
alligators, but alligators also consumed aquatic snakes, and we saw evidence
(FWC marking tags) of alligator remains in stomachs (Rice 2004). We
Figure 2. Mean fish proportion (± SE) in alligator stomach contents among Lakes
Griffin, Apopka, and Woodruff during 2001–2003.
2007 A.N. Rice, J.P. Ross, A.R. Woodward, D.A. Carbonneau, and H.F. Percival 103
observed no evidence of fresh alligators in stomachs. Alligator eggshells
were found in 2 Lake Griffin alligator samples (one female and one male
alligator) and in one sample from a female alligator on Lake Woodruff.
Alligator-condition scores (K) for all Lake Griffin alligators ranged from
1.63 to 3.70 (mean = 2.66 ± 0.045), while K for all Lake Apopka alligators
ranged from 2.15 to 4.13 (mean = 2.99 ± 0.059), and the K for all Lake
Woodruff alligators ranged from 1.86 to 3.08 (mean = 2.48 ± 0.041) (Fig. 3).
The condition of alligators differed among lakes (P < 0.001).
Impaired alligator samples
Thirteen stomach samples from impaired alligators were collected from
Lake Griffin during 2001 and they exhibited some similarities and some
differences to normal Lake Griffin alligator diets. Eight of the 13 samples
contained only old prey, and most (6) were almost completely empty. The
proportion of stomach samples containing old prey (62%) was higher than that
of normal Lake Griffin samples (26%) (Rice 2004). Fresh prey identified in
these samples included fish, reptiles, and invertebrates, similar to samples
from normal alligators. Two of the 5 samples containing fresh prey contained
multiple specimens of D. cepedianum, and 7 of the 8 samples containing old
prey contained prey remains that could not be identified beyond fish.
Table 2. Lake Griffin alligator stomach content samples by year showing the proportion of fish
consumed and the proportion of shad in alligator diets during 2001–2003. Note that 8 out of 10
shad in 2001 were identified as D. cepedianum, and that the one shad found in all the 2003
samples was not considered fresh, and therefore no biomass estimations were made.
# Total fish % Fish % Shad
Year samples biomass (g) biomass (g) biomass # Shad biomass
2001 24 12,312.4 7875.2 64 10 38
2002 42 18,568.4 7998.1 43 0 0
2003 19 6566.7 4436.2 68 1 0
All years 85 37,447.5 20,309.5 54 11 12
Table 3. Lake Griffin alligator fish consumption by year and family, including minimum
number of individuals (MNI) identified and estimated mass in grams of fresh fish consumed
2001 2002 2003
MNI Mass (g) MNI Mass (g) MNI Mass (g)
Total fish 22 7875 24 7998 9 4436
Ictaluridae 6 2044 13 4620 5 2389
Clupeidae 10 4618 0 0 0 0
Lepisosteidae 2 1003 2 2075 2 1411
Centrarchidae 1 150 4 183.1 1 635
Poeciliidae 2 0.2 1 0.4 0 0
Cyprinodontidae 0 0 2 8.6 1 1.2
Cichlidae 0 0 1 700 0 0
Amiidae 0 0 1 411 0 0
Unidentified fish 1 60 0 0 0 0
104 Southeastern Naturalist Vol. 6, No. 1
This study confirmed previous studies indicating alligators are opportunistic
carnivores that consume a variety of prey (Chabreck 1972, Delany and
Abercrombie 1986). Fish were the dominant prey group for alligators in all
three lakes in this study; however, the species of fish consumed differed
among lakes. This may be due more to habitat differences that support a
different composition of fish species rather than dietary preference.
Our hypothesis that alligator mortality on Lake Griffin was due solely to
a diet high in D. cepedianum with high levels of thiaminase causing depressed
levels of thiamin in alligators was not supported by this study. Lake
Griffin alligators did have depressed thiamin levels and were consuming a
large proportion of shad that had high levels of thiaminase in 2001 (Ross et
al. 2003). The drop in morality at Lake Griffin coincidental with the shift in
diet away from shad to catfish (Ichtaluridae) does support the hypothesis,
but Lake Apooka data does not support it. In addition, Lake Apopka alligators
consistently ate large quantities of shad, also containing high levels of
thiaminase (Ross et al. 2003), throughout the study, but there was no unusual
adult mortality occurring on Lake Apopka.
The drop in consumption of shad in Lake Griffin alligator diets after 2001
was most likely due to shad removal by the St. Johns River Water Management
District (SJRWMD). Just prior to Spring 2002 alligator sampling, almost
500,000 kg of D. cepedianum and an estimated 12,000 kg of Lepisosteus spp.
(Gar) were removed from Lake Griffin as part of lake restoration and management
efforts to reduce phosphorus levels (Walt Godwin, St. Johns River Water
Figure 3. Mean condition (± SE) of alligators from Lakes Griffin, Apopka, and
Woodruff during 2001–2003.
2007 A.N. Rice, J.P. Ross, A.R. Woodward, D.A. Carbonneau, and H.F. Percival 105
Management District, Palatka, FL. unpubl. data). Shad removal likely altered
fish populations and certainly changed size distributions of shad in the lake and
thus,their availability to alligators. Shad netting efforts ceased in February
2003 due to absence of large shad in the catch.
Alligator mortality on Lake Griffin was unusually high compared to
other Florida lakes from 1999 through 2001 (Fig. 1—note that this figure
includes only Lake Griffin data); however, by 2003, the number of alligators
dying was not very different from typical mortality levels (D.A.
Carbonneau, pers. comm.). Several factors in and around Lake Griffin occurred
in 2002 that could have affected this decrease in alligator mortality:
water levels rose sharply in early 2002 after heavy winter rains in 2001, the
marsh flow-way restoration system was reactivated, large quantities of shad
and gar were removed, and water quality improved as indicated by reduced
chlorophyll levels (Rice 2004). Whether alligator mortality was linked to
these events is uncertain. However, a significant change in the species
composition in alligator diets coincided with these events.
Alligator condition can be affected by diet, prey density, alligator density,
habitat, ambient temperatures, or other factors (Delany et al. 1999,
Taylor 1979, Zweig 2003). Alligator condition in this study was different
among lakes, and Lake Griffin alligator condition ranged between the condition
of alligator on Lakes Apopka and Woodruff and appeared to be a
healthy size. Insufficient measurements were taken during 2001 to compare
the condition of impaired and normal alligators from Lake Griffin. However,
impaired Lake Griffin alligators did not appear to be thinner or have a lower
condition than normal Lake Griffin alligators.
Thiamin deficiency in crocodilian farms has occurred; however, little has
been mentioned on how or if this deficiency affects body condition.
Huchzermeyer (2003) described thiamin deficiency in crocodilians, but does
not mention if body condition was affected. Jubb (1992) reported on thiamine
deficiency in hatchling Crocodylus porosus Schneider (Saltwater Crocodile)
and mentioned that hatchlings affected by thiamine deficiency were the
largest in their clutch group. We did not see evidence of poor body condition
in impaired or normal Lake Griffin alligators, and it may be that this deficiency
caused a rapid onset of impairments that did not affect their condition.
Lake Griffin alligators did have depressed thiamin levels and did consume
D. cepedianum with high levels of thiaminase; however the combination of
Lake Griffin alligators consuming less shad, the shad removal, and improving
water quality all may have contributed to the number of impaired and dead
Lake Griffin alligators observed and recorded by researchers decreasing after
2001. In addition, shad in Lake Apopka also had high levels of thiaminase
(Ross et al. 2003), and Lake Apopka alligators were consuming greater
amounts of D. cepedianum relative to Lake Griffin without showing mortality
rates similar to Lake Griffin alligators (Appendix 1). An unknown factor that
we did not detect in Lake Griffin may have contributed to the alligator
mortality, and this unknown factor was not affecting Lake Apopka and
therefore did not affect the alligators there. As of 2004, alligator mortality on
Lake Griffin has returned to levels observed prior to the mortality event.
106 Southeastern Naturalist Vol. 6, No. 1
Arnold Brunnell, John White, Chris Visscher, and Jason Williams, Florida Fish
and Wildlife Conservation Commission, provided essential field assistance. Field
and lab technicians Chris Tubbs, Tony Reppas, Esther Langan, Jeremy Olson, Chad
Rischar, and Patricia Gomez were indispensable. The Florida Museum of Natural
History’s (FLMNH) ornithology, mammology, ichthyology, herpetology, and zoo
archaeology collection managers and their reference collections were invaluable
with species identification. Christina Ugarte and Hardin Waddle provided valuable
comments on this manuscript. The St. Johns River Water Management District
(Contract SF624AA), Lake County Water Authority, Florida Fish and Wildlife
Conservation Commission, Florida Museum of Natural History, and the Florida
Cooperative Fish and Wildlife Research Unit provided funding, facilities, and/or
equipment. Access to Lake Woodruff was provided by permit, and this research was
approved by the University of Florida IACUC.
Barr, B.R. 1994. Dietary studies on the American Alligator, Alligator mississippiensis,
in southern Florida. M.Sc. Thesis. University of Miami. Coral Gables, FL. 73 pp.
Barr, B.R. 1997. Food habits of the American Alligator, Alligator mississippiensis, in
the southern Everglades. Ph.D. Dissertation. University of Miami. Coral Gables,
FL. 243 pp.
Brown, J.H., and G.B. West (Eds.). 2000. Scaling in Biology. Oxford University Press,
New York, NY. 352 pp.
Burt, W.H., and R.P. Grossenheider. 1980. Peterson Field Guide: Mammals, 3rd
Edition. Houghton Mifflin Company, New York, NY. 289 pp.
Canfield, D.E., Jr., R.W. Bachmann, and M.V. Hoyer. 2000. A management alternative
for Lake Apopka. Lake and Reservoir Management 16:205–221.
Casteel, R.W. 1974. A method for estimation of live weight of fish from the size of
skeletal remains. American Antiquity 39:94–97.
Chabreck, R.H. 1972. The foods and feeding habits of alligators from fresh and saline
environments in Louisiana. Proceedings Annual Conference of Southeastern Association
of Game and Fish Commission 25:117–124.
Delany, M.F., and C.L. Abercrombie. 1986. American Alligator food habits in northcentral
Florida. Journal of Wildlife Management 50:348–353.
Delany, M.F, A.R. Woodward, and I.H. Kockel. 1988. Nuisance alligator food habits
in Florida. Florida Field Naturalist 16:86–90.
Delany, M.F, S.B. Linda, and C.T. Moore. 1999. Diet and condition of American
Alligators in 4 Florida Lakes. Proceedings Annual Conference of Southeastern
Association of Fish and Wildlife Agencies 53:375–389.
Dunning, J.B., Jr., 1993. CRC Handbook of Avian Body Masses. CRC Press, Inc, Boca
Raton, FL. 371 pp.
Fernald, E.A., and E.D. Purdum. 1998. Water Resources Atlas of Florida. Institute of
Science and Public Affairs, Florida State University, Tallahassee, FL. 309 pp.
Fitzgerald, L.A. 1989. An evaluation of stomach-flushing techniques for crocodilians.
Journal of Herpetology 23:170–172.
Garnett, S.T. 1985. The consequences of slow chitin digestion on crocodile diet
analysis. Journal of Herpetology 19:303–304.
Green, A.J. 2001. Mass/length residuals: Measures of body condition or generators of
spurious results? Ecology 82:1473–1483.
2007 A.N. Rice, J.P. Ross, A.R. Woodward, D.A. Carbonneau, and H.F. Percival 107
Heinz, G.H., H.F. Percival, and M.L. Jennings. 1991. Contaminants in American
Alligator eggs from lakes Apopka, Griffin, and Okeechobee, Florida. Environmental
Monitoring and Assessment 16:277–285.
Honeyfield, D.C., S.B. Brown, J.D. Fitzsimons, and D.E. Tillitt. 2005. Early mortality
syndrome in Great Lakes Salmonines. Journal of Aquatic Animal Health
Hoyer, M.V., and D.E. Canfield, Jr. 1994. Handbook of Common Freshwater Fish in
Florida Lakes. University of Florida Press, Gainesville, FL. 178 pp.
Huchzermeyer, F.W. 2003. Crocodiles Biology, Husbandry, and Disease. CAB
Publishing, Cambridge, MA. 337 pp.
Janes, D., and W.H.N. Gutzke. 2002. Factors affecting retention time of turtle scutes
in stomachs of American Alligators, Alligator mississippiensis. American Midland
Jubb, T.F. 1992. A thiamine responsive nervous disease in Saltwater Crocodiles
(Crocodylus porosus). Veterinary Record 131:347–348.
Magnusson, W.E., E.V. da Silva, and A.P. Lima. 1987. Diets of Amazonian crocodilians.
Journal of Herpetology 21:85–95.
Reitz, E.J., I.R. Quitmyer, H.S. Hale, S.J. Scudder, and E.S. Wing. 1987. Application
of allometry to zooarchaeology. American Antiquity 52:304–317.
Rice, A.N. 2004. Diet and condition of American Alligators (Alligator
mississippiensis) in three central Florida lakes. M.Sc. Thesis. University of
Florida, Gainesville, FL. 89 pp.
Rice, A.N., J.P. Ross, A.G. Finger, and R. Owen. 2005. Application and evaluation of a
stomach flushing technique for alligators. Herpetological Review 36:400–401.
Ross, J.P., D. Carbonneau, S. Terrell, T. Schoeb, D. Honeyfield, J. Hinterkopf, A.
Finger, and R. Owen. 2002. Continuing studies of mortality of alligators on
central Florida lakes: Pathology and nutrition. Final Report to St. Johns River
Water Management District, Technical report series SJ2002-SP6: 34 pp. and 8
annexes. Available online at http://sjr.state.fl.us/programs/outreach/pubs/
techpubs/pdfs/SP/SJ2002-SP6.pdf. Accessed January 2005
Ross, J.P., A.N. Rice, D. Carbonneau, and D. Honeyfield. 2003. Assessment of
effects of diet and thiamin on Lake Griffin alligator mortality. Final report to St.
Johns River Water Management District, Technical report series SJ2003-SP2: 36
pp. and 6 annexes. Available online at http://sjr.state.fl.us/programs/outreach/
pubs/techpubs/pdfs/SP/SJ2003-SP2.pdf. Accessed January 2005
Schoeb, T.R., T.G. Heaton-Jones, R.M. Clemmons, D.A. Carbonneau, A.R. Woodward,
D. Shelton, and R.H. Poppenga. 2002. Clinical and necropsy findings
associated with increased mortality among American Alligators of Lake Griffin,
Florida. Journal of Wildlife Diseases 38:320–337.
SPSS Inc., 2000. SPSS base 11.0 for Windows User’s Guide. SPSS Inc. Chicago, IL.
Sutton, S.G., T.P. Bult, and R.L. Haedrich. 2000. Relationships among fat weight,
body weight, water weight, and condition factors in wild Atlantic salmon parr.
American Fisheries Society 129:527–538.
Taylor, J.A. 1979. The foods and feeding habits of subadult Crocodylus porosus
Schneider in northern Australia. Australian Wildlife Research 6:347–359.
Tillitt, D.E., J.L. Zajicek, S.B. Brown, L.R. Brown, J.D. Fitzsimons, D.C.
Honeyfield, M.E. Holey, and G.M. Wright. 2005. Tiamine and thiaminase status
in forage fish of salmonines from Lake Michigan. Journal of Aquatic Animal
Woodward, A.R., H.F. Percival, M.L. Jennings, and C.T. Moore. 1993. Low clutch
viability of American Alligators on Lake Apopka. Florida Scientist 56:42–64.
Zweig, C.L. 2003. Body condition index analysis for the American Alligator (Alligator
mississippiensis). M.Sc. Thesis. University Florida, Gainesville, FL. 49 pp.
108 Southeastern Naturalist Vol. 6, No. 1
Appendix 1. Fresh prey identified in alligator stomach samples including the numbers identified, estimated mass, and percent composition by live mass for Lakes
Griffin, Apopka, and Woodruff, FL during 2001–2003. The only vertebrate species identified to species level, but not considered fresh were Alligator
mississippiensis (American Alligator), Kinosternon subrubrum Lacépède (Florida Mud Turtle), and Gallinula chloropus/Fulica americana L. (Common
Lake Griffin Lake Apopka Lake Woodruff
Mass Mass Mass
Prey ng % ng% ng%
Shad, Dorosoma spp.Rafinesque 2 1322 3.5 42 3854 21.8
Gizzard shad, Dorosoma cepedianum Lesueur 8 3296 8.8 10 3210 18.1 4 1830 11
Centrarchidae 3 103.1 0.3 6 503 3
Sunfish, Lepomis spp. Rafinesque 1 80 0.2 5 351 2
Warmouth L. gulosus Cuvie in Curvier and Valenciennes 1 144 1
Redear sunfish, L. microlophus Günther 3 257 2
Spotted sunfish, L. punctatus Valenciennes in Cuvier and Valenciennes 1 136 1
Black crappie, Pomoxis nigromaculatusLesueur in Cuvier and Valenciennes 2 785 2.1 1 253 1.4 1 80 0.5
Largemouth bass, Micropterus salmoides Lacepède 1 2696 26.4
Bluegill, Lepomis Macrochirus Rafinesque 4 26 0.1
Gar, Lepisosteus spp. Lacepède 6 4489 12 2 2826 16 1 424 3
Catfish, Ameiurus spp. Rafinesque 11 3890 10.4 7 1387 7.8 3 1600 10
Brown bullhead, A. nebulosus Lesueur 11 4586 12.2 2 701 4
Yellow bullhead, A. natalis Lesueur 2 577 1.5
Mosquito fish, Gambusia holbrooki Girard 2 0.2 0.001
Cichlidae 1 200 1.1
Tilapia, Oreochromis spp.Günther 1 700 1.9 8 3378 19.1
Bowfin, Amia calva Linnaeus 1 411 1.1 1 1763 11
Sailfin molly, Poecilia latipinna Lesueur 1 0.4 0.001
Killifish, Fundulus spp. Lacepède 2 8.6 0.02
Lake Eustis pupfish, Cyprinodon variegatus hubbsi Lacepède 1 1.2 0.003
Golden shiner, Notemigonus crysoleucas Mitchill 1340.2
Needlefish, Strongylura marina Walbaum 21821
2007 A.N. Rice, J.P. Ross, A.R. Woodward, D.A. Carbonneau, and H.F. Percival 109
Lake Griffin Lake Apopka Lake Woodruff
Mass Mass Mass
Prey ng % ng% ng%
Catfish, Pterygoplichthys spp. Gill 1 250 2
Undetermined Fish species 1 60 0.2
Total fish 55 20,309.5 54.2 78 15,869 90 30 10,216 80
Anhinga, Anhinga anhinga Linnaeus 1 1235 3.3 1 1235 7
Double Crested Cormorant, Phalacrocorax auritus Lesson 2 3628 9.7
White Ibis, Eudocimus albus Linnaeus 1 900 2.4
Total birds 4 5763 15.4 1 1235 7 0 0 0
Kinosternidae 1 105 0.3
Stinkpot Turtle, Sternotherus odoratus Latreille in Sonnini and Latreille 6 385 1.0 1 35 0.2 1 108 0.6
Loggerhead Musk Turtle, Sternotherus minor Agassiz 2 150 0.4
Redbelly Turtle, Pseudemys nelsoni Carr 1 1148 3.1
Turtle, Pseudemys spp. Gray 1 13 0.03
Gopher Tortoise, Gopherus polyphemus Daudin 1 582 1.6 1 113 0.6
Florida Softshell Turtle, Apalone ferox Schneider 1 386 1.0
Cottonmouth, Agkistrodon piscivorus Lacépède 1 686 1.8
Brown Water Snake, Nerodia taxispilota Holbrook 1 300 0.8
Mud Snake, Farancia abacura Holbrook 1100.1
Total reptiles 15 3755 10.0 3 158 1 1 108 0.6
Cotton mouse, Peromyscus gossypinus LeConte 1400.2
Eastern wood rat, Neotoma floridana Ord 1 291 1.6
Hispid cotton rat, Sigmodon hispidus Say and Ord 1 155 0.4
Raccoon, Procyon lotor Linnaeus 1 4705 12.6
Round-tailed muscrat, Neofiber alleni True 1 289 1.8
Total mammals 2 4860 13.0 2 331 2 1 289 1.8
110 Southeastern Naturalist Vol. 6, No. 1
Lake Griffin Lake Apopka Lake Woodruff
Mass Mass Mass
Prey n g % n g % n g %
Greater Siren, Siren lacertina Linnaeus 1 387 1 2 1325 8.2
Two-toed Amphiuma, Amphiuma means Garden in Smith 1 287 0.8
Frog, Rana spp. 3 700.4 1.9
Total amphibians 5 1374.4 3.7 0 0 0 2 1325 8.2
Apple snails, Pomacea paludosa Say 64 1321.9 4.0 3 68 0.4 30 694.1 4.3
Total gastropods 64 1321.9 4.0 10 69 0.4 32 695.4 4.4
All other invertebrates combined 224 127.4 0.32 41 87.2 0.558 40 172.3 1.04