We studied diet and size-related dietary patterns among American Crocodiles (Crocodylus acutus) in marine habitats of coastal Belize (1996–1997). Prey items recovered from crocodile (N = 97) stomach contents included insects, mollusks, crustaceans, fish, amphibians, reptiles, birds, and mammals. Based on an overlapping group analysis of percent occurrence, we concluded that hatchlings and small juveniles feed largely on insects and crustaceans, larger juveniles broaden their diet to include fish and nonfish vertebrates, subadults consume increasing amounts of crustaceans with lesser amounts of insects and nonfish vertebrates, and adults subsist primarily on marine crustaceans. Dietary diversity was uniformly low across all size classes but greatest among small and large juveniles. Conversely, hatchlings, subadults, and adults had the most specialized (least diverse) diet owing to reliance upon a limited selection of prey, largely insects (hatchlings) or crustaceans (subadults and adults). Dietary overlap was greatest between adjacent size classes and lowest between the largest and smallest size classes. The high prevalence of freshly ingested prey among all size classes indicates frequent, regular feeding by C. acutus in coastal habitats, perhaps driven by the relatively small size of frequently consumed prey such as crabs. Because crabs have a blood salt content equivalent to the external medium and comprise a large portion of the diet, these prey likely impose a high osmoregulatory burden on C. acutus inhabiting hyperosmotic coastal environments. Contrary to earlier assertions that salt glands in C. acutus lack the excretory capacity to balance salt and water, we suggest populations in coastal Belize rely on these glands in addition to behavioral strategies to maintain osmotic homeostasis.
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Vol. 47 • No. 1