Status and diet of the otter Lutra lutra in Northern Ireland

摘要

We assess the status and diet of otters in Northern Ireland in 2002. Signs of otter presence were noted at 65% of 441 sites surveyed. This figure suggests a decline in signs of otters since the 1980s. Highest occurrence of signs of otters was around lakes, with coastal sites having the lowest occurrence. Percentage occurrence of signs of otter varied considerably with respect to catchment. The highest levels were in Lough Melvin, County Fermanagh, and around the Foyle catchment, County Londonderry; fewest signs occurred along the Antrim coast. Signs of otter occurrence were higher in larger rivers and at unpolluted sites (68%) as compared to polluted sites (57%). Over 50% of otter spraints were composed of stickleback (Gasterosteus aculeatus), salmonids and cyprinids, with stickleback constituting the most frequently occurring prey category. The frequency of occurrence of eels (Anguilla anguilla) in otter diet was found to be consistently higher in spraints collected from smaller streams across all land class groups. The frequency of occurrence of most prey items differed significantly with catchment with the exception of salmonids, which occurred consistently in spraints collected throughout all catchments in Northern Ireland. The current investigation confirms that otters remain widespread in Northern Ireland. However, otters may be feeding on less profitable prey items. Further investigations into the relationship between water quality, prey availability and prey selection are required to fully understand the factors affecting otter diet in Northern Ireland.