Opossum Facts

The opossum (order Didelphimorphia) is the only marsupial found in the Americas. The Virginia opossum (Didelphis virginiana) is the single species found in the United States, but at least 103 species occur in the Western Hemisphere. The word "opossum" comes from the Powhatan or Algonquian name for the animal, which roughly translates as "white dog." Although the opossum is commonly called a possum, some marsupials in the Eastern Hemisphere are also called possums (suborder Phalangeriformes).

Description

Didelphimorphs range from the size of a rodent to that of a domestic cat. The Virginia opossum (Didelphis virginiana), which is also known as the North American opossum, varies in size according to its habitat and sex. Opossums in the northern portion of their range are much larger than those that live further south. Males are much larger than females. On average, the Virginia opossum ranges from 13 to 37 inches in length from nose to the base of the tail, with a tail adding another 8 to 19 inches of length. Males weight between 1.7 and 14 pounds, while females weigh between 11 ounces and 8.2 pounds.

Virginia opossums have gray or brown fur and white, pointed faces. They have hairless prehensile tails, hairless ears, and opposable thumbs on their rear paws.

As with other marsupials, the female has a bifurcated vagina and a pouch, while the male has a forked penis.

Habitat and Distribution

Opossums live in North, Central, and South America. The only species found in North America is the Virginia opossum, which lives along the West Coast of the United States, and from the Midwest all the way to the East Coast and throughout most of Mexico and Central America. However, climate change has been extending the Virginia opossum's range into Canada. Although the opossum prefers a wooded habitat, it is highly adaptable and often lives in urban environments.

Diet

The opossum is a nocturnal omnivore. It is primarily a scavenger, feeding on carcasses, garbage, pet food, eggs, fruit, grain, and other plants. Opossums also eat insects, other small invertebrates, birds and their eggs, rodents, and frogs.

Behavior

The opossum is best known for "playing possum" or "playing dead." When a possum is threatened, it initially responds by hissing and baring its teeth, but further stimulation triggers an involuntary response that puts the animal in a near-coma state. The possum falls onto its side with open eyes and mouth and expels a stinky fluid from its anus that basically causes it to smell like rotten meat. Its heart rate and breathing slow, but the animal remains fully conscious. The response repels predators that avoid carcasses. "Playing possum" isn't under the opossum's control, so an opossum knows what is going on around it, but can't simply get up and leave when a threat has passed. The feigned death may last a few minutes or up to six hours.

Opossums do not hibernate in winter. Since they don't dig dens or build burrows, the animals seek shelter when temperatures drop. In cold habitats, they commonly overwinter in garages, sheds, or under homes.

Reproduction and Offspring

The average opossum estrous cycle is 28 days, but the number of litters they bear per year depends on the species. The Virginia opossum breeds between December and October, with most young born February through June. The female has between one and three litters per year.

Opossums are solitary animals. The male attracts the female by making a clicking sound. The pair separates after mating. As marsupials, females give birth to numerous young (as many as 50) very early in development. The young climb from their mother's vagina to teats within her pouch. A female only has 13 teats, so at most 13 young may survive. Typically only eight or nine young, called joeys, emerge from the pouch after two and a half months. The joeys climb onto their mother's back and stay with her for four or five months before venturing out on their own.

In the wild, an opossum lives one to two years. This short lifespan is typical of marsupials. In captivity, an opossum may live up to four years, but it still ages rapidly.

Conservation Status

The conservation status of the opossum depends on the species. Some species are threatened or extinct. The only type of opossum found in North America is the Virginia opossum, which the IUCN classifies as "least concern." Although hunted, trapped, and accidentally killed, Virginia opossums are abundant and generally increasing in population.

Opossums and Humans

The major cause of opossum mortality is motor vehicle collision. Opossums are hunted for fur and food. Their fat is high in essential fatty acids and may be used in therapeutic skin salves.

Although not aggressive, the opossum is not an ideal pet. First, it's illegal to keep an opossum as a pet in many states unless you have a wildlife rehabilitation license or wildlife hobby permit. Even then, the creatures are challenging to keep because they are nocturnal animals that require a varied diet and have inherently short lifespans. Wild opossums are useful to have around because they control tick, rodent, and snake populations. Unlike many mammals, they aren't susceptible to rabies.

Sources

• De Barros, M. A.; Panattoni Martins, J. F.; Samoto, V. Y.; Oliveira, V. C.; Gonçalves, N.; Mançanares, C. A.; Vidane, A.; Carvalho, A. F.; Ambrósio, C. E.; Miglino, M. A. "Marsupial morphology of reproduction: South America opossum male model." Microscopy Research and Technique. 76 (4): 388–97, 2013. 
• Gardner, A.L. "Order Didelphimorphia". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 6, 2005. ISBN 978-0-8018-8221-0.
• McManus, John J. "Behavior of Captive Opossums, Didelphis marsupialis virginiana", American Midland Naturalist, 84 (1): 144–169, July, 1970. doi:10.2307/2423733
• Mithun, Marianne. The Languages of Native North America. Cambridge University Press. p. 332, 2001. ISBN 978-0-521-29875-9.
• Pérez-Hernandez, R., Lew, D. & Solari, S. Didelphis virginiana. The IUCN Red List of Threatened Species 2016: e.T40502A22176259. doi:10.2305/IUCN.UK.2016-1.RLTS.T40502A22176259.en