Free-ranging house cats in urban and rural areas in the north: useful rodent killers or harmful bird predators?

The prey of 66 free-ranging urban and rural house cats Felis catus was studied in a mainland area in SW Finland. The data included 1624 home-brought prey animals, of which 92 % could be identified at least to the class level. The mean number of prey brought home was 4.1 per cat per month (excluding winter). Rodents were the most common prey (72 %), 18 % of prey being birds, 5.4 % insectivores, and the rest other mammals (hares, least weasels, pine martens, and a bat), reptiles or amphibians. Six "super predator" cats accounted for 40 % of all prey items captured. There were no differences between the sexes in the number or diversity of prey brought home. The prey of young cats was more diverse than that of older, more experienced cats. Especially old cats in rural areas benefit humans by killing many rodents. The proportion of birds captured was 24 % in urban areas where cats represent a possible threat to native birds: probably > 1 million prey animals are monthly killed by free-ranging cats in Finland, at least 144000 of these being birds. "Super predator" cats should thus be kept in the house, especially in urban areas, to prevent predation on birds.