Mice contaminate considerably more food than they eat. They are a health hazard as they carry many diseases and they contaminate food with their urine and droppings. The average mouse sheds 70 droppings in 24 hours and urinates constantly. Droppings are 2-4mm long, black, thin and brittle. Mice become sexually mature at 8-10 weeks and each pair can produce up to 8 litters per year. A litter can contain up to 16 young.

Mice should not be confused with the dormouse, which is a protected species. Doormice are rarely found indoors and can most easily be identified by their furry tail, other mice have bald tails.

Rats and mice avoid all new food and objects, so acute poisons tend to be ineffective (an acute poison is one which they eat and die immediately afterwards). As a defence mechanism, for any new food they eat a tiny amount and go away and will not touch it again if they become ill, therefore chronic poisons are more effective ie poisons which they eat, go away, do not feel ill, come back, eat some more and by the time they feel ill, they have a lethal dose.