Diet of the otter Lutra lutra inhabiting a forest stream in SW Poland

Abstract

Diet of the otter inhabiting a forest stream in SW Poland was studied in order to show the impact of the otter on fish and other aquatic animals. The diet was examined by means of spraint analysis. A total of 157 spraints were collected from 14 sites, and 605 prey items were extracted. Fish comprised the staple diet. It was supplemented by frogs, birds, small mammals and invertebrates. Fish were represented by at least 23 species belonging to seven families. Two families Cyrinidae and Percidae dominated the fish component of the diet (together 70.1%). The most numerous fish species consumed were Perca fluviatilis (24.1%) and Rutilus rutilus (12.1%). The otter diet was most diversified in the coldest months of the year (November-April; B = 10.0-10.5), and least in the warmest months of the year (July-August; B = 5.7). The niche breath was wider in 2006 (B = 12.2), compared with 2007 (B = 20.4). However, only the proportions of Gobio gobio and Esox lucius were statistically different in those two years compared. This study confirms previous findings that the otter is a generalist piscivorous predator hunting opportunistically on locally and seasonally most common fish species, mainly of low economic importance.