Brazilian opossum, Rainforest opossum, Laboratory opossum (in research)
The Gray short-tailed opossum (Monodelphis domestica) is a South American member of the family Didelphidae. Unlike most other marsupials, it does not have a true pouch. The Gray short-tailed opossum is used as a research model in science and is also frequently found in the exotic pet trade. It is also known as the Brazilian opossum, rainforest opossum, and in a research setting the laboratory opossum.
Gray short-tailed opossums are relatively small animals, with a superficial resemblance to voles. As the common name implies, their tails are proportionately shorter than in some other opossum species, ranging from 5 to 9 centimeters (2.0 to 3.5 in). Their tails are only semi-prehensile. The fur is greyish brown over almost the entire body, although fading to a paler shade on the underparts, and with near-white fur on the feet. Only the base of the tail has fur, the remainder being almost entirely hairless. The claws are well-developed and curved in shape, and the paws have small pads marked with fine dermal ridges. Unlike many other marsupials, females do not have a pouch.
Gray short-tailed opossums are found generally south of the Amazon River, in southern, central, and western Brazil. They also occur in eastern Bolivia, northern Paraguay, and Formosa Province in northern Argentina. These little creatures live in rainforest environments, scrubland, and agricultural land, and often visit man-made structures, such as houses.
Gray short-tailed opossums are nocturnal, being most active in the first three hours after dusk. Although they may occasionally shelter in natural crevices in the rock, they normally spend the day in concealed nests constructed of leaves, bark, and other available materials. The nests of females are more complex and tightly woven than those of males. They are solitary, coming together only to mate, and with each individual occupying a home range of 1,200 to 1,800 m2 (13,000 to 19,000 sq ft), flagged with scent marks. The approach of another member of the species is commonly met with hissing and screeching, which may escalate to defensive strikes launched while the animal is standing on its hind legs. Gray short-tailed opossums hunt primarily by scent, poking their snout into vegetation in search of prey or dead animals to scavenge. Once they find living prey, they pounce on it, holding it down with their forefeet while delivering a killing strike, often to the base of the neck, with their sharp teeth.
Gray short-tailed opossums are carnivores and scavengers. They mainly eat rodents, frogs, reptiles, and invertebrates, and supplement their diet with some fruit.
Gray short-tailed opossums are polygynandrous (promiscuous) which means that both males and females have multiple partners during the breeding season. They breed year-round when the climate is suitable, being able to raise up to 6 litters of 6 to 11 young each during a good year. Gestation lasts 14 days, after which the young attach to a teat, where they remain for the next 2 weeks. Like all marsupials, the young are born undeveloped; in this species, they are just 1 centimeter (0.39 in) in length and weigh 0.1 grams (0.0035 oz) at birth. The young grow hair at around 3 weeks, open their eyes about a week later and are weaned at 8 weeks of age. Gray short-tailed opossums become reproductively mature at 5 to 6 months of age.
There are no major threats facing Gray short-tailed opossums at present.
According to IUCN Red List, the Gray short-tailed opossum is locally common throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
