Exotic species as the main prey items of the Neotropical otter in the Atlantic Forest, southeastern Brazil

Abstract

In this work, the diet of Neotropical otter was characterized in four different hydrographic regions in the southern portion of the Central Atlantic Forest Ecological Corridor, in southeastern Brazil. This was done using scat analysis to determine whether diet composition and the proportion of food items vary between studied regions, and which factors may influence the eventual observed differences. A total of 581 scat samples was taken in the environment and identified prey based on the analysis of undigested structures (scales, bone fragments, exoskeleton) and comparison to the structures contained in a reference collection. All prey were described by large prey groups (classes), and fish and crustaceans were identified to the genus level. The frequency of occurrence for each prey item and the food niche breadth were calculated for each region and for the entire study area. Diet similarities between the regions were visualized by a cluster analysis followed by a Principal Coordinate Analysis from the normalized frequencies. The differences in the prey composition of otter diets were compared among the regions by PERMANOVA. Otters showed a predominantly piscivorous diet, in which exotic cichlids were the main prey. Crustaceans was the second most consumed group. The variations recorded for the otter diet were independent of the study region, which may be related to the food variability among rivers/sampled segments in each region, which in turn may be influenced by differences in habitat structures, including the composition of aquatic biota.