Small Pets

Fancy Mouse

Mus musculus

A small, agile climber best kept for observationBeginner

Lifespan: 1.5-3 years
Size: 7-10 cm body, plus tail
Social needs: Social; females live in same-sex groups, males usually solo
Time: Daily feeding and checks; regular cleaning
Cost: Low
Diet: Quality mouse/rodent mix plus occasional fresh food

Overview

What is this animal?

The fancy mouse is a small, agile and inquisitive rodent bred in many colours and coat types.
Mice are mainly nocturnal but active enough by day to make engaging, low-cost pets.

Their small size and short lifespan suit keepers who enjoy observation more than handling.
They are social and need careful group management, with males usually kept singly because they fight.

Temperament

Fancy mice are lively, curious and quick, often more interested in exploring than being held, though calm, regular handling can tame them.
Watching them climb, burrow and forage is the main appeal of keeping them.

Females are social and content in groups, while most males must live alone to avoid serious fighting.
Provide ample space and enrichment to reduce squabbles, and introduce new females carefully on neutral ground.

A good fit for

Beginners and observation-focused keepers
Those wanting a low-cost small pet
Keepers happy with female groups
People who enjoy climbing-focused setups

Common mistakes to avoid

Housing male mice together (fighting)
Pine or cedar bedding harming airways
Cages with escapable bar gaps
Ignoring early respiratory signs

Enclosure

Minimum 50 litres (13 US gallons) — for the pair

Cannot be kept alone. The minimum is 2, and the space above is for that group.

House mice in a gnaw-proof glass or barred enclosure of at least 50-60 litres with secure, narrow bar spacing, as they squeeze through tiny gaps.
Provide deep substrate for burrowing plus vertical climbing structures.

Add ropes, branches, tunnels, a small solid-surface wheel and nesting material.
Females live well in same-sex groups, but males usually fight and often need solo housing.
Keep enclosures clean, as mice can produce a noticeable odour.

Check your enclosure

Supplies

Setup

Enclosure of an adequate size
Water bottles, bowls, hides and enrichment
Carrier and travel box
Digital kitchen scale

Ongoing

Quality mouse or rodent mix
Small dried mealworms
Fresh vegetables for tiny daily portions
Water bottle plus brush
Shallow ceramic dish
Untreated apple or willow chews
Airtight food storage tub

Safe substrate: Dust-extracted paper bedding · Kiln-dried aspen shavings · Hemp bedding

Work out the cost

Care routine

Daily

Feed and clear yesterday's leftovers
Fresh water
Quiet time at the cage
Spot-clean the enclosure
Watch them while they are awake

Weekly

Partial bedding changeevery 5 days
Hands-on health check
Rotate enrichment
Weigh-in

Monthly

Check nails and teeth
Check supplies and dates

Vet: Six-monthly exam — every 6 months (every 3 months from 1 years old)

Top resources for more info

Independent creators and organisations we would send a friend to. We have no affiliation with any of them, and nothing here is sponsored. Links checked 2026-09-19.

YouTubers

EmiologyMouse care, housing and enrichment alongside rats Victoria RaechelHamster and rabbit care, cage setups and honest myth-busting Scotty's AnimalsGuinea pig and small-animal care from a rescue volunteer

Sites

American Fancy Rat & Mouse AssociationUS society with care sheets for pet mice and rats The National Mouse ClubUK fancy-mouse club with care information RSPCA: miceHousing, diet and health guides for pet mice

Go deeper

Diet

Offer a quality mouse or rodent mix of seeds, grains and pellets, supplemented with occasional small amounts of fresh vegetables, fruit and protein such as a mealworm.
Scatter feeding encourages natural foraging.

Provide constant fresh water from a bottle.
Limit fatty seeds and sugary treats to prevent obesity.
A varied but controlled diet keeps these small, fast-metabolism animals healthy.

Health

Mice are prone to respiratory infections, so good ventilation and dust-free, ammonia-free bedding are important; avoid pine and cedar shavings.
Mammary and other tumours are common in older mice, especially females.

Watch for sneezing, weight loss, lumps and overgrown teeth.
Their short lifespan means health changes progress quickly, so seek an exotics vet early.
Regular gentle handling helps you spot problems sooner.

Is your enclosure big enough?

Minimum volume50 litres (13 US gallons)

CompanyCannot be kept alone. The minimum is 2, and the space above is for that group.

Length

Width

Height

Units

Is this urgent?

Small mammals are prey animals. They mask pain and illness by instinct, so by the time something is obvious it is usually already advanced.

Go now

Not eating, or eating far less than normalCall an exotics vet. Bring a recent weight if you have one. In a hindgut fermenter the gut slows and then stops when food stops moving through it. This is the single most common emergency in small mammals.

8 hours

No droppings, or droppings suddenly tiny, misshapen or scarceCall an exotics vet now. Take a photo of the litter tray. Output is the most reliable read on gut movement there is, and it fails before the animal looks unwell.

8-12 hours

Sitting hunched, pressed to the floor, unwilling to moveGo now. A hunched, still posture in a prey animal is a pain posture.

Now

Audible teeth grinding or crunchingGo now. Soft tooth purring is contentment. Loud, slow grinding is pain.

Now

Hard, bloated or drum-tight abdomenGo now. Do not offer food or attempt to massage the abdomen. Gas or an obstruction can become fatal within hours and needs imaging, not home care.

Now

Laboured breathing, open-mouth breathing, or clickingGo now. Keep the animal cool and undisturbed in transit. Most small mammals are obligate nose breathers; open-mouth breathing means they are already struggling.

Now

Maggots or fly eggs anywhere on the animal, especially the rearGo now. Do not attempt to wash them off first. Flystrike can kill within a day. Risk rises sharply in warm weather and in any animal with a dirty or damp rear.

Now

Today

Head tilted persistently to one side, or circlingBook today. Several causes, most of which respond far better to early treatment.

Today

Weight down 5 percent or more since the last weighingCall today, and bring the weight history. Weight falls before appetite visibly changes. This is why weekly weighing is worth the two minutes.

Today

Soon

Drooling, wet chin, or dropping food while trying to eatBook a dental check. Continuously-growing teeth can overgrow into the tongue or cheek long before the animal stops trying to eat.

A few days

Scratching hard enough to break skin, or bald patches spreadingBook an appointment. Mites and fungal infections spread, and some transfer to other animals in the household.

A few days

Have the number of an exotics-competent practice saved before you need it. Most general small-animal clinics do not treat rabbits or rodents out of hours, and finding one at 11pm is not realistic.

This is general guidance for a healthy adult, not a diagnosis. An exotics vet who knows your animal always overrides it — and the time to find one is before you need one.

Can a fancy mouse eat that?

Most small companion mammals are hindgut fermenters: the gut is a fermentation vessel that has to keep moving, and sudden rich food stops it.

Check a food

The full list

Never (19)

AlcoholNo safe amount at any body weight on this site.

never

AvocadoPersin, concentrated in the skin, stone and leaves. Implicated in cardiac damage across birds, rodents and reptiles.

never

Bread and baked goodsRefined starch ferments in the hindgut and causes gas and stasis. No nutritional case for it either.

never

CaffeineCoffee, tea and energy drinks. Cardiac and neurological toxicity at tiny doses for an animal this size.

never

ChocolateTheobromine and caffeine. Small mammals and reptiles cannot clear either.

never

DairyAdults are lactose intolerant and the gut flora cannot handle it.

never

Dried fruitSugar concentrated several times over, and it sticks to the teeth. Most commercial small-pet treats are exactly this.

never

GarlicSame allium toxicity as onion, and more concentrated by weight.

never

Iceberg lettuceAlmost entirely water with negligible nutrition, and it contains lactucarium, which causes diarrhoea in quantity. It displaces food that would have been useful.

never

LeekAllium family. Same mechanism as onion and garlic.

never

MeatA hindgut fermenter has no way to process animal protein. It disrupts the gut flora the animal depends on.

never

MushroomsNot part of any of these animals' natural diet, and the risk from misidentified varieties is not worth the zero upside.

never

NutsFat and phosphorus loads a herbivore is not built for, and a choking risk.

never

OnionOrganosulphur compounds damage red blood cells. The whole allium family is out.

never

PotatoSolanine in the skin and any green part, plus a starch load the hindgut cannot handle.

never

Raw beansLectins. Also a gas producer in a species that cannot vomit or belch.

never

RhubarbVery high in soluble oxalate, high enough to cause acute kidney injury. The leaves are worse than the stalks.

never

Salty or seasoned human foodSalt, oil and seasoning. Crisps, chips, seasoned leftovers and processed meat are all out.

never

SweetcornThe hulls are indigestible and are a recognised blockage risk in small herbivores.

never

Rare treats (13)

AppleSugar. The seeds contain a cyanogenic compound and must be removed. A thin slice, once or twice a week. Never the seeds or core.

rare treat

BananaVery high in sugar and starch, and most animals will overeat it given the chance. A slice the width of a fingernail, rarely.

rare treat

BlueberrySugar, but a small portion size makes it easy to control. One or two berries, twice a week.

rare treat

Brussels sproutsHighly gas-forming. Half a sprout, rarely.

rare treat

CarrotSold as the archetypal rabbit food and it is nothing of the kind: carrot is a root vegetable with a high sugar content. The leafy tops, by contrast, are an excellent green. A thin slice as a treat. The tops can be fed freely.

rare treat

CauliflowerOne of the most gas-forming brassicas. A very small piece, occasionally.

rare treat

GrapesVery high in sugar. Halve them, because a whole grape is a choking hazard. One halved grape, rarely.

rare treat

OrangeAcidic and sugary; can irritate the mouth and gut. A tiny segment, rarely if at all.

rare treat

PearSugar. Remove the seeds. A thin slice occasionally.

rare treat

PeasHigh in starch and sugar. The pods and leaves are better than the peas. A few pods occasionally.

rare treat

StrawberrySugar, though lower than most fruit. The leaves are actually the better part. Half a small berry, once or twice a week.

rare treat

TomatoThe ripe flesh is safe in small amounts. The leaves, stems and any green fruit contain solanine and must never be offered. A small piece of ripe flesh, occasionally. Never the plant.

rare treat

WatermelonSugar and a very high water content, which together can loosen the gut. Remove the seeds. A small cube in hot weather, rarely.

rare treat

Occasional (17)

BasilSafe and well liked. Rotate rather than relying on it. A few leaves.

occasional

Bok choyGood green, mildly goitrogenic like other brassicas. A leaf or two a few times a week.

occasional

BroccoliNutritious but a notable gas producer. Leaves and stalk are better tolerated than the florets. A small floret or a piece of stalk, twice a week.

occasional

CabbageA brassica. Gas-forming in quantity, and goitrogenic with heavy long-term feeding. A small piece, once or twice a week.

occasional

CelerySafe and well liked. Cut across the stalk so the long fibres cannot catch. A short piece, cut into segments.

occasional

ChardSame oxalate issue as spinach. A small leaf, occasionally.

occasional

CourgetteSafe and mild. Serve raw. A few slices a few times a week.

occasional

CucumberSafe, but it is mostly water with very little in it. Useful for hydration in warm weather, poor as a staple. A few slices.

occasional

DillSafe in rotation. A few fronds.

occasional

Green beansSafe cooked or raw in small amounts. Gas-forming in quantity. One or two, occasionally.

occasional

KaleHigh in calcium and a mild goitrogen. Genuinely nutritious, but not the everyday green it is often sold as. A leaf or two, two or three times a week.

occasional

MintSafe in small amounts; strongly flavoured and not every animal wants it. A leaf or two.

occasional

ParsleyNutritious but relatively high in calcium. Fine in rotation, not as the whole green portion. A few sprigs, a few times a week.

occasional

PumpkinSafe and well tolerated in small amounts. A small cube occasionally.

occasional

RocketPeppery and well tolerated in rotation. A small handful, a few times a week.

occasional

SpinachHigh in oxalates, which bind calcium and contribute to bladder sludge and stones in animals prone to them. A single small leaf, no more than once or twice a week.

occasional

WatercressNutritious, strongly flavoured, high in calcium. A small handful occasionally.

occasional

Everyday foods (6)

Bell pepperOne of the best everyday vegetables here: high in vitamin C, low in sugar, no oxalate problem. Remove the seeds and stalk. A few strips daily.

everyday food

Carrot topsThe leaves are a proper green and much better food than the root. A handful as part of the daily greens.

everyday food

CorianderWell tolerated, aromatic, and most animals take it readily. Part of a daily mixed handful.

everyday food

Dandelion leavesOne of the best greens available, and free. Pick well away from roadsides and anywhere that may have been sprayed. A generous handful daily.

everyday food

Grass hayShould be about 80 percent of what this animal eats, available at all times. It is what wears the teeth down and what keeps the gut moving. Unlimited, always.

everyday food

Romaine lettuceDark leafy lettuce with real nutritional content and a good water balance. A generous handful daily as part of a mixed selection.

everyday food

That food is not on our list. Do not offer it on a guess — check with an exotics vet, or leave it out. Nothing in a small mammal's diet is urgent enough to risk it.

Introduce any new food one at a time, in a small amount, and wait two days before adding another. A change in droppings is the earliest signal that something did not suit.

What it really costs

Setup, monthly, first year and across a whole life, itemised and with the electricity worked out from the actual wattage. Published figures for the same animal disagree by a factor of four, so the calculator shows ranges rather than picking one.

Region

How many animals

Your electricity price, per kWh

Buying the setup

Bedding and substrate

Bedding has three jobs: absorb, stay dust-free, and let the animal dig. Anything aromatic is failing the second one.

Safe

Dust-extracted paper beddingThe default for almost every small mammal. Look for 'dust extracted' on the label rather than 'natural'.

safe

Kiln-dried aspen shavingsThe one wood that is fine, because it has no aromatic phenols. Kiln-dried matters.

safe

Hemp beddingVery absorbent and low dust. More expensive per litre but goes further.

safe

Soft meadow hay as a top layerFood and bedding at once for rabbits, guinea pigs and chinchillas. Never the only absorbent layer.

safe

Plain shredded paper or paper stripsUnprinted or soy-ink only. Cheap nesting material; poor as the main absorbent layer.

safe

Fleece liners over an absorbent layerOnly works with an absorbent layer underneath and a wash every few days. Fleece alone holds urine against the skin.

safe

With a caveat

Cardboard-based beddingFine, but it goes soggy quickly and needs changing more often than paper.

with a caveat

Sand bathsCorrect and important for chinchillas, degus and gerbils. Use plain chinchilla bathing sand, never 'dust' products and never builder's sand.

with a caveat

Hemp or straw pelletsGood absorbency, but too hard to burrow in. Use under a soft layer, not as the whole substrate.

with a caveat

Never

Pine and cedar shavingsThe aromatic phenols that make them smell pleasant are the problem: they damage the liver and kidneys and the cells lining the airway. Laboratory work found liver enzyme changes in mice after roughly a day of cedar exposure, taking well over a week away from it to settle, and enlarged livers in mice kept on pine for months.

never

Raw corncobTwo separate problems. It is swallowed and causes intestinal blockage, and it grows mould readily once damp.

never

Cotton wool and fluffy nesting materialSold as bedding, and it wraps around limbs and is swallowed. Repeatedly implicated in amputations in hamsters.

never

Scented or perfumed bedding of any kindAdded fragrance is an airway irritant in an animal whose nose is centimetres from the bedding all day.

never

Clumping cat litterSwallowed during grooming, and it clumps just as effectively inside the animal.

never

SawdustDust plus, usually, softwood. Both problems at once.

never

This is our general list for small pets. We have not built one specific to Mice yet.

Depth matters as much as material for burrowing species. A hamster needs 25 cm or more of substrate it can actually tunnel through; shallow bedding on a large floor is still an inadequate enclosure.