Mouse
Females live happily in groups and adult males do not. Nocturnal, quick to tame with regular handling, and a life measured in a couple of years.
Overview
Mice are the smallest thing on this shelf and the quickest to breed, which is the practical fact that decides how you keep them. A female cycles every four to six days, carries for about three weeks, and can produce five to ten litters a year, so a mixed pair is a colony by the end of the season.
The social rule runs the other way from the hamster's. Females live well in groups and adult males generally do not, since dominant males hold territory and fight over it. Adults weigh 12 to 30 grams with a body of 65 to 95 millimetres, and they live about two years in captivity, with five on record.
Temperament
Quick, inquisitive and easy to tame with regular gentle handling, though they never stop being fast. A mouse out of its cage is a mouse you may not catch again.
They are nocturnal, they explore constantly, and males produce complex ultrasonic songs at frequencies people cannot hear. Buck mice also have a stronger smell than does, which is one of the practical reasons most keepers choose a group of females.
Care and grooming
A plain mix and a pellet, with fresh food in small amounts, and clean water always. They eat very little at a time and cache the rest.
Mice are prone to respiratory disease, so bedding matters: no pine or cedar shavings, and no dusty substrate. Sneezing, clicking breathing or a hunched posture means a vet rather than a wait and see.
Living and exercise
They climb, unlike gerbils, so height and ropes and levels all get used. A deep base for digging plus a tall section to climb is the ideal combination.
Bar spacing is the thing people get wrong: a mouse fits through a gap that looks impossible, and an escaped mouse in a house is usually gone for good. A glass tank with a mesh lid avoids the problem entirely.
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