Small Pets

Short-tailed Opossum

Monodelphis domestica

Solitary pouchless marsupial, warmth-loving and hands-on · Intermediate

Overview

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.

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.

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.

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.

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.