Mouse — care sheet

Beginner. Small, inexpensive and genuinely easy to house well — but with real rules that catch beginners out: they must live in the right same-sex company (and adult males usually can’t share), they need a big tank with deep bedding to dig, and shop mis-sexing causes surprise litters. Get the grouping and the enclosure right and the day-to-day is simple.

Mice are opportunistic omnivores. Feed a good-quality, balanced mouse food (a proper mix or pellet) as the base, plus small amounts of fresh fruit and vegetables as part of — not on top of — the daily ration, scattered to encourage foraging. Provide constant fresh water. Don’t feed grapes, raisins or rhubarb (poisonous to mice) or lettuce (it causes diarrhoea).

A large, secure, escape-proof enclosure (a big tank or a cage with very narrow bar spacing — mice squeeze through tiny gaps) with plenty of floor space and, crucially, deep bedding to dig and tunnel in. Add hides, nest sites and things to climb. Keep the enclosure in a settled spot out of direct sun.

Mice are social and shouldn’t be kept alone (unless a vet specifically advises it for an aggressive individual). Keep them in compatible single-sex groups: females generally do very well in groups, while adult males are often aggressive toward one another and frequently can’t be housed together — the safest male groups are same-litter brothers grouped before weaning and never disturbed. Never introduce unfamiliar adult males. Keep established groups stable.

Mice are very sensitive to heat. Keep the cage out of direct sunlight and away from temperature extremes and high humidity (not a conservatory, garage, bathroom or air-conditioned room), and move it somewhere cooler in a summer heatwave.

A deep layer of safe bedding — at least about 2 cm and ideally deeper so they can dig — of non-aspen wood chips, cellulose-based chips or shredded filter paper, plus plenty of nesting material (mice are keen nest-builders). Avoid fine sawdust, wood shavings, aspen, and any fragrant or dyed bedding, which can cause health problems.

Give mice lots to do: deep substrate to burrow, nesting material to build with, tunnels, safe climbing, a solid exercise wheel, and food scattered around the cage to forage for (foraging is a core natural behaviour). Provide safe things to gnaw for their continuously-growing teeth.

Mice keep themselves clean and don’t need bathing. The main upkeep is monitoring: provide gnaw items so their teeth wear down, and check for overgrown front teeth, lumps, or skin problems. Their small size means changes are easy to miss, so a regular close look matters.

None needed on a good-quality, balanced mouse diet.

Tiny — adults weigh about 28 g and are roughly 6–8 cm (2.5–3.5 in) long in the body, plus a tail about the same again. Males are usually larger than females.

Short — typically 1.5 to 2.5 years.

See a small-animal or exotics vet if you notice: Sniffling, sneezing, a chattering noise, nasal discharge or laboured breathing — respiratory infection is common in mice (often Mycoplasma, which has no cure); see a vet; Diarrhoea, loss of appetite or weight, a hunched posture, or rough, ruffled fur; Any lump or swelling (mammary tumours are common in mice); Scratching, hair loss, scabs or flaky skin (possible mites or skin disease); Overgrown front teeth, or difficulty eating.