The gray short-tailed opossum is a small South American marsupial from the scrub and forests of Brazil, Bolivia, and Paraguay, and despite the name, though both are American opossums, it belongs to a separate, far smaller genus than North America's Virginia opossum.
It is named for its tail, which is short relative to its roughly 12-15cm body rather than long and fully prehensile like the larger opossums.
Unlike almost every other marsupial kept as a pet, the female has no pouch, so her litter of up to thirteen pups clings to nipples on her belly.
It is strictly nocturnal and, importantly, strictly solitary, which sets it apart from the intensely social sugar glider it is sometimes confused with.
Adults meet only to breed and will fight, often to the death, if housed together.
It is a major laboratory model, the first marsupial widely bred for research, so much of the pet supply traces back to colony stock, and captive animals are only lightly domesticated and vary widely in how tame they become.
Housing
As a tropical species it must be kept warm, between about 24 and 30C, with a slightly warmer basking area and no cold drafts, because chilling quickly leads to respiratory illness.
Never let the enclosure fall into the upper teens Celsius.
House a single animal in a securely lidded glass tank or vivarium giving at least a 40-gallon-breeder footprint, roughly 90x45cm of floor and 45cm or more of height, with larger and more enriched always better, since caging studies show cramped animals become stressed.
These opossums are determined climbers and escape artists that squeeze through small gaps, so every seam must be secure and any mesh no wider than about 1cm.
Provide deep substrate for burrowing and a covered nest box, since they build nests and hide away by day.
Add branches, cork bark, and hides so they can use the vertical space, plus a large solid-surface running wheel of about 28cm or more so the back stays fairly straight and the tail cannot be caught.
Keep humidity moderate, around 50 percent, spot-clean often because males in particular scent-mark, and site the enclosure out of direct sunlight and away from household noise.
Diet
This is a primarily insectivorous omnivore, so the core of the diet is live insects such as gut-loaded crickets and dubia roaches, with fatty mealworms and waxworms offered only as occasional treats.
Dust the insects with a calcium and vitamin D3 supplement at most feedings, because calcium deficiency causes metabolic bone disease in this species.
Offer a stable base alongside the live prey, such as a quality commercial insectivore diet or a little high-protein food like cooked lean meat or a good grain-free cat food.
Add small amounts of fruit and vegetables, and give an occasional pinky mouse or a little hard-boiled egg as variety rather than a staple.
Avoid sugary foods and rich, fatty feeders, as captive short-tailed opossums gain weight easily and obesity shortens their lives.
Provide fresh water at all times, from a bottle or a shallow bowl they cannot tip.
Health
The most common preventable problems are metabolic bone disease from low calcium and obesity from overfeeding rich insects, both driven by diet and both avoidable.
Older animals are prone to cataracts and dental disease, and the species is a well-known laboratory model for UV-induced skin cancer, so keep the enclosure out of direct sunlight and off sunny windowsills.
Cold exposure readily triggers respiratory infections, which makes stable warmth a health requirement rather than a comfort.
Their lifespan is short, roughly three to six years with typical captive animals reaching three or four, so problems progress quickly and early veterinary attention matters.
Sudden weight loss, lethargy, laboured breathing, limb weakness, or a wet or dirty rear warrants an exotic vet promptly.
Very few clinics see marsupials, so confirm you have an exotic-savvy vet before you acquire one.
Temperament
Short-tailed opossums are curious and can become genuinely interactive, but they are not cuddly lap pets and tame best when handled gently and daily from a young age.
They are fast, can leap, and may nip or gape defensively if startled or woken abruptly, so handle them low over a contained surface and rouse them gently.
Each animal has its own temperament, and some laboratory-line individuals stay skittish no matter how much time you invest.
They communicate and mark with scent, and males can be noticeably musky, which regular cleaning keeps in check.
Above all they are strictly nocturnal, territorial loners that must live alone, so plan for a single animal, expect an evening pet, and never keep two together outside brief, supervised, intentional breeding.
A good fit for
Keepers wanting a solitary, low-social exotic
Homes that can hold a steady 24-30C
People comfortable feeding live insects daily
Patient handlers who tame from a young age
Night owls and observant adults, not young children
Common mistakes to avoid
Housing two together, which causes fatal fights
Cold drafts that trigger respiratory illness
Calcium-poor diets that cause metabolic bone disease
Overfeeding fatty insects, leading to obesity
Expecting a cuddly, sugar-glider-like companion
Few exotic vets treat marsupials, so line one up first
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 short-tailed opossum 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.
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate
Intermediate