Species · Omnivore rodent
Mouse
Mus musculus
The tiny, budget-friendly enclosure-nerd’s pet — quick, curious, and best kept in the right same-sex group.
Difficulty: BeginnerPrintable care sheet →
Mice are the tiny, quick, endlessly busy pet for people who love watching an animal build, burrow and forage. They’re social and cheap to keep well — but the social side is exact: female mice thrive in groups, adult males usually fight, and a lone mouse is a lonely one. Give them a big tank with deep substrate and the right cage-mates, and they’re a delight. This is the honest guide — what’s normal, what’s urgent, and what the shop got wrong.
Care at a glance
| Adult size | 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. |
|---|---|
| Lifespan | Short — typically 1.5 to 2.5 years. |
| Enclosure | 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. |
| Companionship | 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. |
| Temperature | 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. |
| Bedding & substrate | 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. |
| Enrichment & exercise | 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. |
| Grooming & upkeep | 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. |
| Diet | 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). |
| Supplements | None needed on a good-quality, balanced mouse diet. |
🤎 Did you know? — Mouse fun facts
Little true delights about the mouse — each one checked against a named source, no pet-shop myths.
- Male mice serenade females with complex ultrasonic “songs”, pitched far too high for us to hear.Animal Diversity Web
- For their size mice are real athletes — nimble climbers, jumpers and swimmers that can sprint around 8 mph.Animal Diversity Web
- Mice “read” the world through their whiskers, feeling air currents and surface textures as they move.Animal Diversity Web
What it's like to live with a Mouse
Life with mice is a window into constant small industry — building nests, stashing food, exploring tunnels, mostly after dark. They’re fast and light, so gentle, low, patient handling (never grabbing) keeps them calm and safe from falls. Males tend to have a stronger scent than females because of scent-marking. Because they’re prey animals that hide illness and their lives are short, watching appetite, weight and breathing is the best early-warning system you have.
Your first month together
The settling-in period, in order — so you know what's normal and when not to worry.
- Let them settle before much handling; win trust with food and slow, low contact rather than grabbing.
- Confirm the group is same-sex and correctly sexed (shop mis-sexing is common and leads to surprise litters).
- Keep the existing diet at first and change it gradually; set up deep bedding for digging.
- Learn their normal — activity, appetite, breathing and droppings — and watch a new group for aggression, especially among males.
- Find an exotic vet that sees mice; at their size, problems escalate quickly.
Through the year, and as they grow
Summer heat is the main risk — keep mice cool and out of the sun. Respiratory infections spread more easily in stuffy or dirty conditions, so keep on top of cleaning year-round. Given a lifespan of only 1.5–2.5 years, watch closely for lumps and breathing changes as they age.
Fancy mouse varieties
Fancy mice come in many coat types, patterns and colours — but they are all one species with the same core care. Most of the variety is purely cosmetic; a couple, though, carry a genuine health or breeding implication worth knowing before you pick one.
- Standard, Satin & Long-haired (Angora) — Coat types — a smooth glossy coat, a high-sheen “satin”, or a longer “angora” coat. The long coat needs no trimming, but long and curly coats are worth a routine check for soiling and eye irritation.
- Rex / Frizzie (Astrex) — A wavy, curly coat with curly whiskers. Purely cosmetic — cared for exactly like any other mouse.
- Hairless — ⚠️ Little or no fur. Needs extra warmth and draught protection, and hairless lines can be more health-fragile (they’re linked to immune weakness) — best left to experienced keepers.
- Marked & patterned (Dutch, Broken, Banded, Tan/Fox) — White-and-colour patterns and tan-bellied types. Cosmetic only.
- Red / Fawn / Yellow — ⚠️ The gene that makes a mouse red or yellow (“lethal yellow”, Ay) can’t be bred true — paired with itself it’s fatal in the womb — and living reds are prone to obesity, infertility and a shorter life. Keep them lean; a genuine welfare point, especially for breeders.
- Albino & other colours (black, blue, chocolate, dove, champagne…) — Cosmetic. Albino (pink-eyed white) mice can’t make melanin, so just avoid direct sun.
These are appearance varieties of one species — for most, the core care is identical (covered in the mouse care guide on this page). The two exceptions above (hairless mice needing warmth; the “red/yellow” gene’s health and breeding risks) are the ones genuinely worth factoring into your choice.
Sources: AFRMA — recognised mouse varieties · AFRMA — The Red Mouse (lethal-yellow gene) · FOUR PAWS — Mice as pets (hairless/curly welfare) · National Mouse Club — breed standards
The pet store gets these wrong
Common myths, kindly corrected — no shame for having believed them.
- Two adult male mice usually can’t live together — they often fight seriously, so males frequently need to be housed alone or only as never-separated litter brothers.
- Mice aren’t “feeder animals” or disposable — a pet mouse is a sentient animal that needs company, space and care.
- A tiny pet-shop cage isn’t enough — mice need a large enclosure with deep substrate to dig.
- Shop-sexed mice are often mis-sexed — check the sexes yourself to avoid an accidental litter.
- Not all “safe veg” is safe — skip lettuce (diarrhoea) and grapes, raisins and rhubarb (toxic).
Before you buy
- Can you keep them in the right same-sex group (and house males separately if they fight)?
- Can you provide a large enclosure with deep bedding to dig?
- Can you check/confirm their sex to avoid accidental litters?
- Do you have an exotic vet that treats mice, given how fast small animals decline?
- Are you prepared for a short life of about 1.5–2.5 years, and to keep them cool in summer?
See a vet if…
We can't diagnose from afar — but these are the signs to stop watching and get a professional:
- 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
Never
- Never house unfamiliar or adult male mice together — serious fighting is likely.
- Never keep a mouse completely alone unless a vet advises it for an aggressive individual.
- Never use a tiny cage or shallow bedding — mice need space and depth to dig.
- Never use fine sawdust, aspen, cedar or fragrant/dyed bedding.
- Never feed grapes, raisins, rhubarb, or lettuce.
Common mouse questions
How hard are Mouses to keep — are they good for beginners?
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.
What do Mouses eat?
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).
How big an enclosure do Mouses need?
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.
Do Mouses need a companion, or can they live alone?
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.
What temperature do Mouses need?
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.
What bedding and substrate do Mouses need?
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.
What enrichment and exercise do Mouses need?
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.
What grooming and upkeep do Mouses need?
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.
What supplements do Mouses need?
None needed on a good-quality, balanced mouse diet.
How big do Mouses get?
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.
How long do Mouses live?
Short — typically 1.5 to 2.5 years.
What are the signs Mouses are sick or need a vet?
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.
Free tools for your mouse
Sources & further reading
This guide was written and fact-checked against these authorities. It's kind, general guidance — not a diagnosis or a substitute for an exotics vet:
- RSPCA — Creating a good home for mice — large enclosure, ≥2 cm deep bedding to dig, heat sensitivity, safe substrates
- RSPCA — What to feed mice — omnivore mix, forage-scatter, avoid grapes/raisins/rhubarb and lettuce
- RSPCA — Keeping mice together — social, single-sex groups, male aggression, pre-group siblings
- Merck Veterinary Manual — Description of mice — adult ~28 g, 6–8 cm body, lifespan 1.5–2.5 yr
- Merck Veterinary Manual — Diseases & Disorders of Mice — respiratory (Mycoplasma), digestive infections, mammary tumours
Written and fact-checked by The Hayfold Team against veterinarian-authored sources — if your pet shows a red-flag sign above, see an exotics/small-animal vet promptly.