Mouse

Fancy mice ("fancy", in this context, means "hobby") are domesticated breeds of the common or house mouse (Mus musculus). The terms fancy and "feeder mice" are often used interchangeably by retailers, and are in fact the same variety of mouse. Fancy mice is a term to describe mice that have been selectively bred for exhibition. They can vary greatly in size, from small pet mice that are approximately 15–17.5 cm (6–7 in) long from nose to the tip of the tail, to show mice that measure 30 cm (12 in) nose to tail. Pet mice weigh about 29–44 g (1.0–1.6 oz) but large show mice can weigh up to 130 g (4.6 oz).

http://en.wikipedia.org/wiki/Fancy_mouse