Food habits and ontogenetic dietary partitioning of American crocodiles in a tropical Pacific Island in Central America

Abstract

Studies on food habits are fundamental to understanding the ecology of a species and its interactions with the community to which it belongs. Among crocodylians, diet affects a variety of biological, physiological, and behavioral characteristics. However, despite having one of the largest distributions across the Americas, some aspects of Crocodylus acutus’ natural history remain poorly studied, particularly in insular areas. We characterized American crocodiles’ food habits in Coiba Island, Panama, assessing ontogenetic dietary variation and dietary overlap by age group and size. We captured and collected stomach content samples from 49 individuals from four transects from March to December 2013. From these samples, we could taxonomically identify three phyla, four subphyla, eight classes, 11 orders, 17 families, 14 genera, and 12 species as prey items. However, not all samples could be identified to the lowest taxon (species), having most of them identified only to family level. Large juveniles had the largest proportion of prey items and subadults the largest proportion of gastroliths and vegetal content. Percent occurrence per major categories (insects, arachnids, crustaceans, fish, reptiles, birds, and mammals) showed crustaceans and insects as the most prominent groups of prey items on this island. Overlapping group analysis showed a reduction in the consumption of invertebrates (crustaceans and insects) as individuals aged. However, these items were the most common throughout all American crocodiles sampled. Dietary overlap analyses showed a likely ontogenetic dietary partitioning with high overlap (>60%) between small and large juveniles and low overlap (<30%) among small juveniles, subadults, and adults. To date, 71 species have been reported as prey items for American crocodiles. However, relying on prey items identified only to genus, we had at least 97 prey items. Thus, C. acutus can be defined as generalist with a broad spectrum of prey inhabiting all types of habitats and having all types of consumption classifications. Overall, American crocodiles inhabiting coastal areas present some differences in both dietary composition and structure with those dwelling inland and freshwater habitats as well as an interindividual diet variation, which reflects the plasticity and adaptability of C. acutus to a variety of conditions.