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.

Freshwater Predators on the Edge: Assessing the Temporal and Spatial Variation in Diet of Largemouth Bass in Mobile Bay Estuary, Alabama, USA

“…Similar methods have been used in other studies of vertebrate diet characterization (Balaguera‐Reina et al. ) and have been used effectively for fish (Bizzarro et al. ).…”

“…Statistical analysis.-We generated accumulation curves for the overall sample and for each season within our data set to determine whether we reached an asymptote in species richness as a function of diets sampled (Ferry and Cailliet 1996). Similar methods have been used in other studies of vertebrate diet characterization (Balaguera-Reina et al 2018) and have been used 164 effectively for fish (Bizzarro et al 2017). Descriptive statistics of diet richness (the number of prey types found in the stomach) and diversity (Shannon's diversity index H 0 ) were calculated for each individual and averaged across individuals within both seasons and sites.…”

Assessing ontogenetic maturity in extinct saurian reptiles

“…Motani, 1999 b ) more mature than a ‘small juvenile’ (e.g. Leardi, Pol & Clark, 2017; Balaguera‐Reina et al ., 2018), or do they simply have different body sizes at the same ontogenetic stages? Is a ‘late juvenile’ (e.g.…”

Use of diet and body condition assessments as intermediate indicators of translocation success in the Critically Endangered Philippine crocodile (Crocodylus mindorensis)

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