Diet of the otter on a pond managed for nature conservation (Csombárd, Somogy county)

Abstract

The role of the small-sized artificial fishponds standing nowadays under natural conservation management may be more considerable in the ecological network than their size suggests. Feeding habits of the piscivor, top predator Eurasian otter (Lutra lutra) are less known in such habitats. Our study sought to analyze feeding habits of the otter in a near-natural system (Csombárdi pond, SW Hungary, 7 ha). The diet composition of the otter was assessed by the analysis of spraint samples (n=1656) collected during four years. Throughout the study period, the main food source of the otter was fish (percentage relative frequency of occurrence, O: 77.9%; percentage estimated biomass consumed, B: 93.2%), composed mainly from small-sized (less than 100 g) individuals. Three fish taxa formed the bulk of otter diet throughout the year, namely Carassius sp., (mainly gibel carp Carassius gibelio), pumpkinseed (Lepomis gibbosus) and perch (Perca fluviatilis). Secondary food resource was amphibians; consumption of birds and other food types was negligible. Otters behaved as opportunistic hunters, preying primarily on the most abundant fish species and size classes. Most of fish eaten (E: 76.1%, B: 79.1%) was non-native. Results may be useful for the conservation of otters, near-natural ponds, and associated native fish communities, furthermore confirm the importance of conserving biodiversity of artificially established habitats.