Common opossum

Class: Mammalia
Order: Didelphimorphia
Family: Didelphidae
Genus and Species: Didelphis marsupialis
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The common opossum is a marsupial with a long, prehensile tail, a robust body and short legs with sharp claws. It is found throughout southern Mexico, Central America and northern South America.

Physical Description
The common opossum has a long, prehensile tail, a robust body and short legs with sharp claws. It has thick, black-gray fur and long guard hairs along its back and flanks and a cream-colored belly. Its face is light with a dark stripe down the forehead. It has long whiskers and little to no hair on its ears and tail. Opossums are sexually dimorphic, meaning males and females exhibit different characteristics. Males of this species are slightly larger than females and have more prominent canine teeth.
Opossums grow to lengths of 10.5 to17 inches (27 to 43 centimeters). Their weight fluctuates by location and range, with reports of opossums weighing as few as 2.2 pounds (1 kilogram) and up to 13 pounds (6 kilograms).
Native Habitat
Common opossums are found throughout southern Mexico, Central America and northern South America. They live in a variety of habitats, including different types of forests and suburban and urban environments. Their range is restricted by elevation and access to water. They are not found above 7,300 feet (2,232 meters) and do not inhabit arid environments.
This species communicates in various ways, but olfactory, auditory and visual displays are their most prominent forms of perception. When threatened, opossums may hiss, growl, screech, spray urine or feces, bare their teeth, sway or drool. They may be best known for "playing dead"—a behavioral adaptation in which the opossum lies motionless to ward off predators. Opossums can play dead for just a minute or up to several hours. This behavior is most common among young individuals.
Food/Eating Habits

Common opossums are opportunistic omnivores. Their diet includes plants, nectar and fruits, as well as both invertebrates and vertebrates, such as birds, amphibians, small mammals and even some venomous snakes. They also eat carrion and occasionally root through human garbage to find food. The opossum's diet fluctuates seasonally, but some items, such as earthworms and grasshoppers, are consumed year-round. Common opossums play a significant role in seed dispersal throughout their range.

At the Smithsonian's National Zoo, the common opossum eats biscuits, greens, vegetables, fruits and meat, including fish, eggs and mice.

Social Structure
These opossums are nocturnal and solitary animals, typically coming together only to breed. They remain in their burrows during the day; their preferred hiding spaces can come in the form of treetops and tree cavities, as well as underground dens and abandoned nests. Common opossums are fairly transient. On average, males spend fewer than two days in a burrow, while females tend to remain in one den for five days before moving on.
Reproduction and Development

Common opossum breeding seasons vary by location. Some have a single, long breeding season that spans from January through September. Others have multiple, shorter breeding windows throughout the course of a year. Females build leafy nests, and males breed with multiple mates, competing for breeding rights. 

These marsupials have a short gestation of just 14 to 15 days. Babies are 0.4 inches (1 centimeter) long when they emerge and weigh less than 0.005 ounces (0.13 grams). Although extremely small and underdeveloped, a newborn opossum has the strength to crawl to its mother's pouch. Once there, it attaches to one of the mother's nine nipples and continues to develop for another 50 days. A female can give birth to a litter of 20 opossums, but those unable to attach to a nipple do not survive. After emerging from the pouch, young remain with their mother, sometimes riding on her back for up to a month and a half until they are fully weaned and independent.

Common opossums in regions with access to ample resources tend to give birth to litters of mostly male offspring, while those in regions with scarce resources tend to have more females in their litters. Additionally, litter size tends to decrease closer to the equator. Litters with as few as two young have been observed.

This species typically survives for less than two years in the wild and for about four years in human care.

Common opossums are considered a widespread and adaptable species. Human-caused mortality is most often due to hunting or collisions with vehicles; opossums are hunted for their fur, meat, as sport or by farmers looking to protect their animals. Opossums are most often hunted when other game becomes difficult to find. In Suriname, common opossum meat is harvested and illegally traded to French Guiana.

As opportunistic feeders tolerant of many different habitats, including suburban areas with significant human development, common opossums do not face significant threats from human development and expansion. No formal protection measures for the species are in place, but common opossums do occur in several protected areas within their natural habitat.

In some areas, opossums are considered pests, because they feed on garbage and are known to carry parasites. Some communities view them more favorably, hunting them for medicinal use. Their natural predators include ocelots, jaguarundis and harpy eagles.

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The Small Mammal House is home to one female common opossum.
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