The American or common opossum (Didelphis marsupialis) is the only member of the order Marsupialia to occur naturally in North America. The American opossum occurs from southern Ontario through to most of South America. The only other member of its genus is D. azarae, which occurs through much of South America. However, other genera and species of the family Didelphidae, the New World opossums, occur in Central and South America.
The usual habitat of both species of opossums is brushy or forested, ranging from an open to a full canopy. However, the common opossum will also feed in fields and other open habitats, as long as they are close to trees. Opossums are solitary animals, coming together only to mate. Northern animals remain active throughout the winter, although they often suffer from frost-bite, which can cause them to lose parts of their ears and the tips of their tail.
Opossums can have a body length as great as 18 in (50 cm), plus a tail of up to 21 in (54 cm). Their pelage consists of a dense underfur, which is variably colored black, brown, red, grey, or white, with scattered, white-tipped guard hairs. The head is light-colored, often with three dark lines extending backward from the snout. The tail is almost naked and prehensile.
Female opossums have a deep, fur-lined, abdominal pouch (or marsupium), usually containing 13 nipples. The young are born in an early stage of development. Although recently born young are tiny (approximately beesized) and virtually helpless, they are able to use their partially developed forelegs to slowly crawl to their mother's pouch, where they suckle and grow until they can move about independently of their parent. As many as 25 babies may be born, but no more than 13 can be accommodated by the number of teats in the marsupium, and usually only about seven to eight babies survive to the point where they can leave the pouch. The weaned young are often carried on their mother's back for some time, until they become fully independent.
Opossums can climb well, and are both terrestrial and arboreal in their habits. They usually spend the day denning in a cavity in rocks, a hollow log, or some other shelter, emerging at night to feed. Opossums are omnivorous in their diet, feeding on a wide range of plant and animal matter, including insects, mice, birds, and frogs that they hunt, as well as carrion.
When struck by a human or other potential predator, a common opossum will often roll onto its back or side and feign death, a behavior known as "playing possum." This may be an involuntary act, possibly induced by a shock-like reaction, and is usually performed with a gaping mouth, a lolling tongue, and closed eyes. This might seem to be a dangerous response to a potentially lethal confrontation, but many predators will not attack a seemingly dead animal.
The fur of opossums killed in the early winter is dense and is sought after by hunters. The common opossum is also eaten in some places, with roasted "possum and taters" considered a delicacy in parts of the southern United States. Opossums can be trapped or hunted at night with hounds and lights. Fortunately, the opossum is quite fecund and has managed to maintain its abundance in spite of rather intense hunting pressures. In fact, the opossum has even expanded its range considerably to the north during the past century.