Social; females live in same-sex groups, males usually solo
Diet
Quality mouse/rodent mix plus occasional fresh food
Time
Daily feeding and checks; regular cleaning
Cost
Low
Overview
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.
Housing
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.
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.
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
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.
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.
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.
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.
Beginner
Beginner
Beginner
Intermediate
Intermediate
Intermediate