Opossums. You've probably seen one staring into the headlights of you car. More likely (and unfortunately) you've passed a lot of possum carcasses along the side of the road. But these common little critters are anything but ordinary.

Most of us are familiar with the term "playing possum." This refers to the opossum's unique ability to fall into a shock-like state when frightened or unable to flee. This is a defense mechanism, fooling potential predators into thinking the opossum is dead, and many predators won't consume dead prey. This is a totally involuntary action that can last for hours. Although not aggressive, they may also try to bluff other animals by baring their teeth and hissing. Predators include people, dogs, cats, owls and other larger wildlife.

Algonquian tribes called the creature apassum or white beast. About the size of a large house cat, opossums are white to gray in color, with a long, round, hairless tail, papery-thin small, round ears and wide jaws with 50 teeth. They have black, beady eyes and a long, pointed nose.

Unlike most other animals, opossums have opposable toes, like thumbs, on their feet. This feature, along with their prehensile tails, adapted to seizing or grasping, allows them to grip tree branches quite effectively. Contrary to popular belief, opossums never hang from their tails while sleeping, because they are just too heavy. Occasionally, the young may hang from their tails but never to sleep.

The opossum is North America's only native marsupial, or pouched animal. Marsupials are primitive mammals from the time of dinosaurs. The female has a fur-lined abdominal pouch where, after birth, the young are carried and nourished. Probably the most well-known marsupials are the kangaroos of Australia. Opossums are solitary creatures, except when breeding. They are also nocturnal, wandering at night and sleeping during the day.

Adult females average about two litters a year, with 5 to 13 babies per litter. For opossums, gestation is very brief, only 12-13 days. When born, the tiny young weigh about 2 grams each and are a half-inch long. They are blind, earless and hairless. Their forepaws are well-developed, though.

Just before birth, the mother prepares a pathway of saliva to the pouch. Using their strong forepaws, the young climb to the mother's pouch, where they will attach to a nipple and continue to develop, remaining for about 2 months. For large litters, those babies that do not find an available attachment site will die of starvation.

When fully developed, they emerge from the pouch but remain with their mother until they are 4 months old. Baby possums sometimes ride on their mother's back, clinging to her fur. Babies are preyed upon by owls, coyotes and dogs.

They currently range from the central states to the East Coast, from the Great Lakes and New England south to Mexico and Florida. Opossums are also found in the Pacific Coast states.

Opossums are extremely adaptable creatures. They will eat just about anything, including mice, rats, birds, insects, snakes, frogs, vegetables, fruits, worms, slugs, snails, carrion and garbage. Some people refer to opossums as nature's little sanitary workers because they consume so many pests and dead animals.

Opossums are also not very particular about where they live. They inhabit woodlands, farmlands and suburbs. They'll seek shelter in old dens of other animals, outbuildings, barns, hollow trees, logs, culverts and brush piles. So keep your eyes peeled, especially at night. You never know when you'll encounter North America's marsupial.