Domestic cats are what conservation biologists refer to as 'subsidised exotic predators'. Their population density can reach more than 100 times that of native carnivores, and around 35% of households own a cat. There have been quite a few studies of domestic cat hunting behaviour, all of which show broadly similar results. Typically, domestic cats spend between 5 and 9 hours per day outside.
About half of these cats hunt, and 70 - 90% of their target prey are small mammals. They frequent gardens and nearby land if it is relatively open (for example, pasture or the fringes of sparse woodland). Scientists monitoring hunting domestic cats observe that they hunt about 5 or 6 times more frequently than their owners estimate.
They manage to capture prey on about a quarter of their attempts. Half of the prey escapes alive, so their total kill rate works out at around 13%, or about 2 kills a week. This kill rate is more than three times as high as owners estimate. Nevertheless, this is quite an inefficient kill rate, and domestic cats are only responsible for low prey numbers in quite small geographic areas.
So long as the metapopulation of prey animals is healthy, and the population density of domestic cats not unusually high, they rarely threaten small mammal populations in Europe, where they have been established for centuries.
Feral cats, as Australia knows to its cost, are an entirely different matter. They are not 'subsidised' (ie not receiving supplementary feeding) and so are hunting for a living.
The domestic or feral cat Felis catus (syn F. sylvestris catus) is a threat to the population of Wild Cat F. sylvestris in the Brenne, as interbreeding is common.
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