Opossums, more often called possums in North America, are the only naturally occurring marsupials – that is, animals that carry their young in pouches – in the United States. ("Opossum vs. possum" is a distinction without a difference; "possum" is merely short for the formal term.) They are relatively celebrated in mainstream culture, with "playing possum" used widely to mean faking being unconscious or unresponsive to escape perceived danger. They stand out for their characteristic waddle and pointy snout, among other distinctive traits. As adults, the largest known possums barely exceed 15 pounds, a statistic that perhaps surprises some people.

Opossums have 50 teeth; a white face; nearly naked ears; a long, nearly conical snout; and a scaly, prehensile tail. ("Prehensile" means "capable of grasping," like a circus elephant's trunk grabbing peanuts.) They have coarse, usually grayish fur. Their forelegs have have toes with claws, while their hindlegs have an opposable thumb and have nails rather than claws on their toes. Opossums were originally found only in the southeastern U.S. but have gradually migrated northward and westward.

The opossum lifespan is notoriously short. They have a high mortality rate as they are often killed by hawks, raccoons and even dogs. Their young, which are born extremely small, are the most vulnerable to predators. It is rare to find a possum over two years old in the wild.

Opossums are more modestly sized than they perhaps appear. While it is not unusual for house cats to top 20 pounds, a possum that large would probably be a world record possum.

To gain an idea of how big possums get in the U.S., the Missouri Department of Conservation lists the largest known specimen at 16 pounds, 2.6 ounces. This is hefty compared to skunks, the biggest of which in Missouri weighed only 7 pounds, 12 ounces, but modest compared to the records for other similar-looking furry creatures in the state, including beavers (73 pounds), badgers (28 pounds, 14.4 ounces) and raccoons (28 pounds, 8 ounces).

What kinds of nourishment helps opossums grow to whatever size they ultimately reach? Realize that opossums are some of the oldest mammals in existence, dating back over 60 million years. Because of the fierce competition for food they have historically faced, they have evolved to be able to eat almost anything.

Their natural diet, such as one exists, is heavy in fruits, nuts, grains; insects, slugs, snakes, frogs, birds (and bird eggs), shellfish and mice; and carrion (dead animals). Around humans, opossums eat garbage, pet food, bird seed, poultry and whatever handouts they can solicit.