opossum (əpŏsˈəm, pŏsˈ–) [key], name for several marsupials, or pouched mammals, of the family Didelphidae, native to Central and South America, with one species extending N to the United States. With the exception of an obscure group found in South American forests, opossums are the only living marsupials outside the Australia–New Guinea region. Extremely abundant despite the encroachment of civilization and apparently little changed over millions of years, they owe their success to their adaptability, omnivorous diet, and rapid reproductive rate. Opossums are more or less arboreal, nocturnal animals, with long noses, naked ears, prehensile tails, and opposable hind toes tipped with flat pads. They eat small animals, eggs, insects, and fruit. The common, or Virginia, opossum, Didelphis marsupialis, ranges from Argentina to the N United States; it is found mostly in wooded areas and is common in the SE United States. The common opossum resembles a large rat, with a white face and long, coarse fur of mixed white-tipped and black-tipped hairs. It spends time both in trees and on the ground and makes nests of leaves, usually in holes in trees. When frightened it goes into a state of collapse; this involuntary "playing possum" sometimes saves it from predators, who lose interest in an apparently dead animal. The female usually has the typical marsupial pouch, although it is absent in some of the South American species. The 6 to 18 young are born after a gestation of 12 days and weigh 1/15 oz. (1.9 grams); they crawl through the mother's fur to the pouch where they are carried and nursed for three months. After emerging, they ride on the mother's back, clinging to her fur or tail with their own tails. Because it raids domestic poultry and corn, the opossum is hunted in the South as a pest, as well as for food and sport. Among the other opossum species are the tiny mouse opossums ( Marmosa species) and the yapok, or water opossum ( Chironectes minimus ), which has webbed feet and leads a semiaquatic existence. The yapok ranges from Guatemala to Brazil. Opossums are classified in the phylum Chordata, subphylum Vertebrata, class Mammalia, order Marsupialia, family Didelphidae.
See study by J. F. Keefe (1967).