A lot of farms, and particularly massed animal farms such as poultry or pig farms, keep cats to control the mouse/rat population. While these cats will "group", it's not so strange because they are usually related. Matilda is a farm cat from Kingsthorpe, and she's a stone killer. From where I'm sitting in my office now I can see three, count 'em, mouse carcasses on the lawn which I'm going to have to go and clean up! At Kingsthorpe the cats are not fed unless they are pregnant or are nursing mothers. They have to find their own provisions. Kingsthorpe has thousands of free range hens so they're never short of tucker ...