The gut content of Hoplobatrachus occipitalis (anura: dicroglossidae) provides an inkling of its age-modulated voracity, prey diversity and choices

Abstract

Notably known to consume small animals, anurans’ diets are sometimes affected by their age. This study examined the diet composition of Hoplobatrachus occipitalis, its prey diversity and preferred taxon using snout-vent lengths (SVLs) as a metric for age. With a non-destructive stomach-flushing technique, the gut contents of each actively captured Hoplobatrachus frogs were introduced into properly labelled vials and their prey items fixed in 70% alcohol for microscopic visualization and identification. Before releasing captured frogs, their SVLs [grouped as small (27 – 56 mm, n = 18), medium (57 – 88 mm, n = 35), and large (89 – 120 mm, n = 6)] were determined. A total of 392 preys belonging to 14 Orders, seven Classes and four Phyla of animals, a twig and pebble were found. The small and medium frogs significantly (p<0.05) preyed on more Hymenopterans (ants) than any taxon, while the large frogs showed no prey preference. The prey taxa among the small frogs were significantly fewer and less diverse with more dominant taxa than those found among the medium frogs, but not the large ones. Nonparametric estimates showed over 80% prey inventory completeness (a metric for sampling efforts); in conformity with taxa-accumulation curves, which approached their asymptotes for small and medium frogs, unlike the large ones, which had 53%. In sum, age-specific differences were seen in the prey contents, diversity and preference of H. occipitalis. Ontogenetic changes, among other plausible implications, may impose nutritional demands that modulate the predator’s choices and voracity.