Cats as ratters or even micers is not something I've really known. Sure they may bring you the odd present doing no harm in the field in but I don't see (at least well fed pet cats) them as being that effective pest controllers.

A friend of mine had a mouse infestation in her flat. A cat of her own wouldn't be practical, she travels too much. But she'd heard that cat fluff was a mouse repellent. So I collected a bagful of surplus fluff from our long-haired lilac tortie Chloe. It worked - she hasn't had mice for a year.

The thing is, Chloe is nearly 19 years old, has almost no teeth, and has probably never caught anything in her life. Any prey would suffer nothing worse than a geriatric gumming. But her fluff seems to be absolutely terrifying.