Opossum is the common name for about 8 genera and 65 species of omnivorous mammals comprising the family Didelphidae, one of 2 families of marsupials found outside of Australia. The Virginia or North American opossum (Didelphis virginiana) is the only marsupial native to Canada. The opossum, poorly adapted to severe cold, reaches the northern limit of its range in Canada and is found in extreme southern Ontario and the lower Fraser Valley, BC.
An easily recognized, cat-sized animal, it has a long, pointed nose, naked ears, coarse black to white fur; scaly, prehensile (grasping) tail; and a hind foot with a clawless, opposable first toe. This species probably evolved from the very similar tropical species D. marsupialis during the Pleistocene (1.65 million to 10 000 years ago).
Young are born in an underdeveloped state after a gestation of less than 13 days; development is completed in a pouch on the mother's belly. In Canada, one litter (2 litters in the rest of its range) of up to 13 young each may be produced annually.