There are more than 60 different species of opossum, which are often called possums. The most notable is the Virginia opossum or common opossum—the only marsupial (pouched mammal) found in the United States and Canada. A female opossum gives birth to helpless young as tiny as honeybees. Babies immediately crawl into the mother's pouch, where they continue to develop. As they get larger, they will go in and out of the pouch and sometimes ride on the mother's back as she hunts for food. Opossums may give birth to as many as 20 babies in a litter, but fewer than half of them survive. Some never even make it as far as the pouch.
Opossums are scavengers, and they often visit human homes or settlements to raid garbage cans, dumpsters, and other containers. They are attracted to carrion and can often be spotted near roadkill. Opossums also eat grass, nuts, and fruit. They will hunt mice, birds, insects, worms, snakes, and even chickens. These animals are most famous for "playing possum." When threatened by dogs, foxes, or bobcats, opossums sometimes flop onto their sides and lie on the ground with their eyes closed or staring fixedly into space. They extend their tongues and generally appear to be dead. This ploy may put a predator off its guard and allow the opossum an opportunity to make its escape. Most times they will growl deeply, raising their pitch as the threat becomes more urgent. Males make a clicking "smack" noise out of the side of their mouths as they wander in search of a mate, and females will sometimes repeat the sound in return. When separated or distressed, baby opossums will make a sneezing noise to signal their mother. If threatened, the baby will open its mouth and quietly hiss until the threat is gone.
Opossums are excellent tree climbers and spend much of their time aloft. They are aided in this by sharp claws, which dig into bark, and by a long prehensile (gripping) tail that can be used as an extra limb. Opossums nest in tree holes or in dens made by other animals. These animals are widespread and are sometimes hunted as food, particularly in the southern United States.