Population Biology of the American Crocodile

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Abstract
The population biology of the American crocodile (Crocodylus acutus) was studied in southern Florida [USA] during 1977-1982. Crocodiles occur primarily in inland mangrove swamps protected from wave action. Females use the open waters of Florida Bay only for access to nesting sites. Individuals have large (86-262 ha), overlapping activity areas. Nesting occurs in spring and summer, avoiding the cold and the wet seasons, either of which can affect incubation. Clutches averaging 38 eggs were laid both in mounds and in holes in the ground, either singly or communally. Available data cannot support the view that the number of nests has decreased in recent years. Hatching failure occurred as a result of infertility, predation, and embryonic mortality from desiccation and flooding. Hole and creek nests were most susceptible to embryonic mortality. Seventy-eight percent of nests hatched some young. We found no evidence of adults defending nests or young, but nest opening by adults was essential for hatching. Disturbance at nest sites caused females to abandon the site. All expected age classes occurred in the population. Size at maturity was 2.25 m TL for females. Documented mortality of adults and subadults of approximately 2 crocodiles per year was predominantly human-caused. At least 45 crocodiles have been released into southern Florida in 17 years. We estimate the southern Florida population to be about 220 .+-. 78 adults and subadults.