An opossum is a cat-sized marsupial with grayish fur, a pointed snout, and a long, mostly hairless tail. Opossums are the only marsupials native to the United States and Canada, which means they carry their babies in a pouch, like kangaroos do. You might spot one waddling through your backyard at night, since they're nocturnal creatures that come out after dark to search for food.

When an opossum feels threatened, it sometimes goes completely limp and appears dead, lying motionless with its tongue hanging out. This reaction, called playing possum, can fool predators into losing interest, since many animals prefer live prey. The opossum might stay frozen like this for minutes or even hours until danger passes.

Despite their somewhat ratty appearance, opossums are actually helpful neighbors. They eat lots of ticks, along with other pests, and they're remarkably resistant to rabies. They're also surprisingly good climbers, using their flexible tails to help them balance and grip branches as they search for fruit and insects.

People sometimes spell and say the word possum, dropping the initial “o,” though technically a possum is a different Australian animal. In everyday American conversation, though, both words can refer to the same shuffling, pointy-nosed creature raiding your garbage cans.