Food habits of the American mink Mustela vison in the Mazurian Lakeland, Northeastern Poland

Food habits of the American mink Mustela vison were studied based on the analysis of 2364 scat samples, collected at three lakes in Northeastern Poland. The mink preyed on a wide range of prey, but two types of prey, amphibians and fish, dominated in the diet of the mink during all the seasons. Frogs, and first and foremost, the common frog Rana temporaria, were hunted by the mink, mainly from the late autumn until the early spring, and comprised up to 83.9% of the prey biomass (the multiannual average for November–December at the Majcz Wielki Lake). The most frequently eaten fish were cyprinids and percids. Seasonality of fish consumption by mink was not as well pronounced as in the case of amphibians. At the first two lakes, fish were hunted mainly in the winter and in the early spring, whereas at the third lake in the summer. The highest multiannual average share of fish in the diet of the mink was recorded in March–April at Lake Tuchlin (69.2% of the prey biomass). Crayfish, which were recorded in the diet mainly in the late spring and in the summer, comprised up to 59.6% of the prey biomass for May–June at the Majcz Wielki Lake. Birds, mammals and insects were supplementary food for the mink. During the breeding season, mink predation on waterfowl and their broods was correlated with the abundance of crested grebe Podiceps cristatus and coot Fulica atra nests in the area. The diet of individual mink varied considerably and the share of birds in the diet of the mink was related to the distance from individual mink dens to the colonies of waterfowl. In May–June, adult birds, chicks and eggs comprised up to 73.6% of the prey biomass of a female mink that inhabited a den located 100 m from the colony's edge. At all three lakes, the diet of the mink was the most diverse in the late spring and in the summer. In May–August, the values of the mink food niche breadths were about twice those noted in winter months.