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.
The name “opossum” is derived from an Algonquian word meaning “white animal.” Also called possum, this cat-sized marsupial shows more variation in size than almost any other mammal. Adult males can measure 1 to 3 feet long from the tip of the nose to the base of the tail and weigh 1.5 to 14 pounds. Ranging from southern Canada down into Costa Rica, they reach their largest size in the north. Using 50 teeth, more than any other North American land mammal, they 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 young (about the size of a honey bee) 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 tend to stay close to their den, but will forage up to two miles during their nightly activities. They crave calcium, eating the skeletons of rodents and road kill they consume; Being slow-moving, they’ll often become road kill themselves. They’re the sanitation workers of the wild and gardeners should not only welcome their diet of pests, but they also show a preference for rotting produce rather than fresh. Scientists performing tests on the transmission of Lyme disease show that possums’ activities effectively “vacuum-up” ticks, and being fastidious groomers they scratch the ticks off and eat them. And due to their low body temperature, disease transmission is extremely low. The researchers determined that a single possum might kill an astonishing 4,000 ticks…in a week!
As animals that originated in the Tropics, opossums can’t bulk up with subcutaneous fat as well as raccoons and other North American mammals, so they are in danger of freezing when temperatures dip below 19 degrees Fahrenheit. So on cold nights, they can’t go out and forage for very long…instead, staying in their dens. With very little fat to supply energy, too many cold nights result in the animal dying. The ones that best endured New England winters are those who lived near people. Urban areas are warmer, and sheds, basements, attics, and other human-related cubbyholes prove to be more comfortable for them than shallow ground holes or tree cavities.
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. Opossum meat was historically a favored food in the Deep South, and ’possum grease was used in traditional medicine as a chest rub for respiratory ailments. Tests rank its intelligence at pig level, above cats and 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. Opossums have been found to be immune to the sting of honeybees, scorpions, serpents, and to toxins such as botulism. And probably because they eat various snakes, they have partial or total immunity to the venom produced by rattlesnakes, cottonmouths and other pit vipers; researchers are studying the toxin-neutralizing factor in opossum blood in hopes that it can be adapted as an anti-venom in humans!
So if you’re lucky enough to have possums pay you a visit, consider their harmless presence a gift of health to you and your family. Maybe even reserve a “possum cubbyhole” for their survival; the springtime tick population will absolutely hate you!!