Opossums are solitary except when mating or caring for young. Female opossums raise 2, rarely 3, litters per year. Young are born 13 days after mating. Young are born blind, hairless, and helpless. When they are ½ inch long, young find their way into the pouch of the female, where they each attach to 1 of 13 teats. About 23 young are born but only those that attach to a teat survive: the rest quickly perish. The average size of a litter is 7 to 8. They remain in the pouch for 7 to 8 weeks and are not weaned until 96 to 108 days after birth. Most young die during their first year. Those that survive until spring breed in that year. Wild opossums may live 2 to 3 years, although they may live twice as long in captivity.
Opossums do not dig their own burrows but use burrows abandoned by other animals. Other den sites include tree cavities, brush piles, rock crevices, and nests of squirrels that have been abandoned. They sometimes den under homes, attics, and garages where they may make a messy nest.
Opossums usually are solitary and nomadic, with a home range of 10 to 50 acres. Young seem to roam randomly until they find a suitable home range. They have a top running speed of 3.5 miles per hour and escape predators by entering burrows, climbing trees, or swimming. When threatened, opossums may bare their teeth, growl, hiss, bite, screech, and exude a yellow-green fluid from the anal glands that smells mildly like the essence of skunks. An opossum may “play dead” by rolling onto its back and going limp, sometimes with the tongue lolling out of its mouth, which may be an involuntary state of comatose. Opossums may appear stupid when captured or surprised, but have ranked above dogs in some tests of intelligence.
Opossums do not hibernate. During very cold weather they enter dens for short periods until temperatures rise. Although they primarily are nocturnal, they may forage during the day, especially in cold weather.
Opossums use diverse habitats that may be arid or moist, forest or field, and urban or rural. They prefer habitat near streams and swamps.
Opossums are opportunistic omnivores. They consume animals and plants including insects, worms, snakes, lizards, mice, rats, grasses, fruits, and vegetables. Opossums may visit compost piles, garbage cans, or dishes of food intended for pets. Opossums often are considered beneficial because they feed on insects, mice, and rats.