128 



Reptiles ami Amphibians — Our Living Resources 



or 1.9% annually. Average annual densities of 

 harvestable alligators increased 2.7%, while 

 average annual densities of adults increased 

 2.5%. The 0.5% average annual increase in 

 counts of juvenile alligators during 1974-92 

 was not significant. These trends confirm that 

 the Florida alligator population increased dur- 

 ing the apparent recovery of the 1970"s and 

 I980"s (Neal 1985). We observed cyclic pat- 

 terns in abundance over time for all size classes 

 (Fig. 2). Cyclic population levels may represent 

 varying availability of counted alligators due to 

 fluctuations in water level not fully accounted 

 for in our analyses. They may also reflect pop- 

 ulation changes brought about by periodic 

 droughts or. to a lesser extent, severe winters. 



0.3 m -1,2m (1-4 ft) 



1.8 m or longer (6 ft or longer) 



74 



76 



78 



80 



82 



84 



86 



90 



92 



Year 



Fig. 2. Annual indice.s (mean 

 number of alligators deteeted per 

 linear kilometer 10.62 mi] of sur- 

 vey route) and smoothed trend 

 estimates (Cleveland 1979) for 

 three size classes of the statewide 

 alligator population in Florida, 

 1974-92. 



From 1983 to 1992. observed densities of 

 adult alligators declined 3.2% per year, but we 

 did not detect such trends in other size classes 

 (Fig. 2). It is too early to draw conclusions con- 

 cerning the influence of harvests on alligator 

 populations since legal harvesting began in 

 1987 because of the variable nature of night- 

 light alligator counts and the uncertain effects 

 of wariness. Relatively stable populations of 

 juveniles and harvestable alligators indicate that 

 hatchling recruitment (replenishment) is suffi- 

 cient to replace alligators lost through harvest. 

 Consequently, alligator harvests do not seem to 

 have negatively affected the Florida alligator 

 population as a whole. 



Historically, the Florida alligator population 

 was threatened by habitat loss and excessive 

 illegal hunting (Hines 1979), but recently envi- 

 ronmental contamination has been associated 

 with population declines. Wetland drainage and 

 alteration during the I900"s destroyed alligator 

 habitat and permanently reduced alligator pop- 



ulations in some wetlands, particularly in fresh- 

 water marshes (Neal 1985). State legislation, 

 most recently the Wetlands Protection Act of 

 1984 (Florida Statutes 403.91), has significant- 

 ly protected remaining wetlands, but alteration 

 and loss of wetlands persist. Between the mid- 

 1970"s and mid-1980's, 10,542 ha (26,030 

 acres) of wetlands per year were lost to agricul- 

 ture and other development (Frayer and Hefner 

 1991 ). Thus, habitat loss remains a threat to alli- 

 gator populations. 



Illegal hunting is now negligible and has 

 been replaced by regulated, managed harvests. 

 Florida implemented a nuisance alligator con- 

 trol program in 1978 in response to increasing 

 problem alligators during the I970"s (Hines and 

 Woodward 1980). Because the nuisance alliga- 

 tor program targets individual alligators, the 

 removal of these animals is unlikely to measur- 

 ably affect alligator populations (Hines and 

 Woodward 1980; Jennings et al. 1989). The 

 state game commission introduced managed 

 harvests of alligators and their eggs in 1987 to 

 create conservation incentives by enhancing 

 economic value of wild alligators (Wiley and 

 Jennings 1990). Studies of the effects of harvest 

 on alligator populations demonstrated that har- 

 vests are sustainable at certain rates (Jennings et 

 al. 1988: Woodward et al. 1992). Annual moni- 

 toring and effective control of harvest rates 

 ensure that populations will not suffer long- 

 term depletion. 



More recently, environmental toxins have 

 been implicated in the shaip decline of the alli- 

 gator population on Lake Apopka. Florida's 

 third-largest lake (Woodward et al. 1993; 

 Guillette et al. 1994). Widespread pollution of 

 wetlands by potentially toxic petrochemicals 

 and metals may threaten the long-term viability 

 of other alligator populations within Florida. 

 For the present, the status of the Florida alliga- 

 tor population is secure; however, continued 

 habitat loss and toxic contamination will nega- 

 tively affect alligator populations and may 

 eventually compromise their conservation. 



References 



Brandt, L.A. 1989. The status and ecology of the American 

 alligator iAIU^alor mississippiensis) in Par Pond. 

 Savannah River Site. M.S. thesis. Florida International 

 University. Fort Lauderdale. 89 pp. 



Cleveland. W.S. 1979. Robust locally weighted regression 

 and smoothing scatteiplots. Journal of the American 

 Statistical Association 74:829-836. 



Frayer. W.E.. and J.M. Hefner. 1991. Flonda wetlands: sta- 

 tus and trends. 1970's to 1980's. U. S. Fish and Wildlife 

 Service. Atlanta. 33 pp. 



Guillette, L.J.. Jr.. T.S. Gross. G.R. Masson. J.M. Matter. 

 H.F Percival. and A.R. Woodward. 1994. Developmental 

 abnormalities of the gonad and abnormal sex hormone 

 concentrations in juvenile alligators from contaminated 

 and control lakes in Florida. Environmental Health 

 Perspectives 102:680-688. 



