Opossums are nocturnal marsupial mammals found in North, Central, and South America. They are not aggressive; when confronted by danger, they freeze and play dead. Their success in terms of niche survival can be explained by their exceptionally sturdy immune systems, their willingness to adapt to new habitats when their previous territory is threatened, and their ability to consume and digest a very wide range of foods in various stages of freshness or rot. Their robust reproductive cycles keep opossum populations thriving.
Poisonous snakebites have little to no effect on opossums. While it is possible for an opossum to carry rabies, it is very rare; they are 80% less likely than other undomesticated mammals to carry the virus. Their exceptionally strong immune systems do not translate into long life, however. On average, opossums only live until the age of four. Their many predators include owls, coyotes, domestic dogs and cats, and humankind.
Dielphimorphia, the scientific name for opossums, are arboreal dwellers with prehensile tails that grip branches like hands. Their flat feet lack arches to permit greater contact with the ground; the opposable "thumbs" on their rear feet help them grip and hold trunks and branches when climbing. Opossum jaws are relatively large, and their tiny incisors, triple-pointed molars, and oversized canine teeth mean they are able to eat whatever foods are available.
Highly opportunistic, in addition to trees, opossums will nest in burrows built and abandoned by other creatures or under homes, barns, or other human structures. They are not built for speed and cannot, therefore hunt. As a result, the opossum body has evolved to accept fruit, leaves, and insects as sources of nourishment. They feast on scavenged road kill and will eagerly consume snakes, frogs, and small rodents. They often live near humans, surviving off garbage and pet food.
The only North American marsupial, opossums can also be found in Central and South America. After a two-week gestation period, the blind newborns crawl through their mother’s fur to reach her pouch, where they attach to a teat. A jill, or female opossum, gives birth two or three times a year to as many as 20 babies less than half an inch (about 1.3 cm) in size. Of these, only 13 can survive, as that is the number of teats in her pouch. The jill’s ability to copulate with several males helps ensure a larger number of pups will survive.