A mouse is a rat-like but small rodent. There are many different species of mouse; the commonest is the house mouse (Mus Musculus), which can be up to 20 cm long (half of its length is its long tail). It lives in all inhabited areas of the world, finding warmth and shelter in human dwellings. In the wild it eats grain, roots, fruit, grass and insects, but it will eat anything edible, sometimes even nibbling soap.

Mice breed rapidly, producing litters of up to 12 young, and in warm conditions such as heated houses they can breed all year round.

They can be a pest if they destroy human food, but in general they are useful to humans, as many predators live mainly on mice and would otherwise eat more valuable animals such as livestock.