Any of several species (family Phalangeridae) of nocturnal, arboreal marsupials of Australia and New Guinea. They are 22–50 in. (55–125 cm) long, including the long prehensile tail, and have woolly fur. All species eat fruits, leaves, and blossoms; some also eat insects and small vertebrates. Possums grasp branches with their hind feet. Most species bear their young in tree hollows and unused birds' nests; a few build leafy nests. Several species are endangered because of predation, fur trapping, or habitat loss, but the common brush-tailed possum is considered a pest. See alsoopossum.