Why has one of my mice lost most of her whiskers and now some fur too?

This can be a relatively common problem when mice are housed together and become mature. It is a problem known to breeders as “barbering”, when one mouse starts to nibble at its companion, shortening its hair. There is no single cause, but stress is often involved.

Ideally, you should separate the mice, and before long, your pet will regrow its fur again. They can then be reintroduced again on neutral territory in the future, and hopefully, the problem will not return if you adjust your pet's housing.

Alternatively, simply try offering more places where your mice can hide in their quarters as a first step. These rodents are naturally shy, and so they can become easily stressed if they do not have access to sufficient areas for this purpose. You may ewant to include a hamster house for example, and you could even use the central cardboard tube from a roll of paper kitchen towelling. This is easily replaced too, if the mice decide to gnaw it.

Generally, try to make their quarters more interesting, and give them special small animal chews, so they can exercise their teeth. Don't worry that there isn't a wide choice of chews available for mice, as again, those marketed for hamsters will be suitable. The problem can also be encountered in pet rats too.