The Isthmus of Panama formed about 3 million years ago. Colliding underwater continental plates created pressure, forming volcanoes that surfaced, and sand, silt, and continental debris filled in the spaces. Atlantic and Pacific waters became isolated, and the Gulf Stream Current was born…its Caribbean waters now flowing northward warming Eastern Europe.
The newly formed land bridge made land-based animal migration possible, and The Great American Biotic Interchange occurred. Deer, bear, wolves, cougars, and others found new habitats in South America and in the newly formed Central America. Animals moving northward included armadillo, porcupine, and the 70 million year old opossum.
Also called possum, this cat-sized marsupial has 50 teeth, more than any other North American land mammal, used to opportunistically feed on plants and animals, foraging during darkness. Their prehensile tail is used for grasping while climbing trees and gathering leaves and other bedding materials. Solitary and roaming, but sometimes huddling together as families in burrows, they’ll remain in an area as long as food and water is available. Like their marsupial kangaroo cousins, male opossums are called jacks, females are called jills, and the young are joeys; a group is a passel.
After a 12-14 day gestation, the many young find their way to their mother’s pouch, where they’ll nurse for another 70-125 days. 5 to 8, but as many as 13 may live to emerge from the pouch, most living for only another year or two. A separated or distressed baby makes a sneezing noise; the mother will respond with clicking sound and waits for the baby to find her. A baby may also open its mouth and quietly hiss until the threat is gone. The young will sometimes hold on to their mothers back while she travels. Possums are the only mammals, other than primates, with opposing “thumbs” on their feet, making them great climbers.
Requiring no special diet or habitat, they’re able to live in many varied areas under various climatic conditions. They’ll eat carrion, rodents, insects, snails, slugs, birds, eggs, frogs, plants, fruits and grains, along with human table scraps, dog food and cat food. They crave calcium, eating the skeletons of rodents and road kill they consume. They’re the sanitation workers of the wild and gardeners should welcome their diet of pests. A single possum will eat 5,000 ticks a year, along with rats and cockroaches.
When threatened, opossums run, growl, belch, urinate and defecate. An involuntary response, like fainting, also happens with adults: “playin’ possum”. They roll over, become stiff, and curl their lips to bare their teeth as saliva foams around the mouth and a foul-smelling fluid is secreted from glands. Their eyes may or may not close. The catatonic state can last for up to four hours, and has proven effective as a deterrent to predators looking for a hot meal.
Wrongly perceived as a giant, dirty, scavenging rat, these harmless creatures have many endearing qualities. Tests rank its intelligence at pig level, above dogs. They are clean animals, using their tongue and paws to groom themselves frequently and thoroughly; largely lacking sweat glands, this behavior is believed to help them cool down. They are also odorless, unless “playing possum”. Due to their low body temperature, possums are highly resistant to rabies, a virus requiring a high body temperature, and are eight times less likely to carry rabies compared to wild dogs. They have partial or total immunity to the venom produced by rattlesnakes, cottonmouths and other pit vipers.