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FAUNA: The uninvited guest

by Mary Parker Sonis

You don’t have to travel to Madagascar to find one of nature’s most unusual mammals. In fact, this bizarre creature can be found rummaging through your trashcan, taking up residence in your garage or boldly walking into your kitchen to cadge a treat from the cat food bowl.

The Virginia opossum is North America’s only marsupial animal, and it has been wandering the continent for more than 70 million years.

A Virginia opossum. Photo by Mary Parker Sonis

As a primitive mammal, the opossum has a life that begins in a very unusual fashion. The placenta of an opossum is rudimentary and cannot support a full-term pregnancy. After a gestation of 14 days, the raisin-sized embryonic joeys are born. They are sightless, without fur and have undeveloped limbs. The mother then licks her abdomen to make it easier for her young to wriggle and slide their way into her marsupium (pouch), where they each attach to one of her 13 nipples.

Many of these tiny young never manage to attach to a nipple, while others may perish by attaching to a nonfunctioning nipple. A mother opossum’s maximum number of joeys can never be more than 13, but usually a smaller number survive.

For the next two months, these babies remain in the pouch, where they complete their development. At two months, the young joeys emerge from their mother’s pouch and climb onto her back, where they spend another six weeks.

A Virginia opossum. Photo by Mary Parker Sonis

The little opossum joeys hang onto their mother’s fur using their extremely adept five-fingered paws. Their hind feet feature an opposable digit that functions much like a thumb. Humans are the only other creatures in North America to have opposable digits.

The tracks of opossums are distinctive for their tiny hand-like appearance. The digits are well spread, and the hind track looks like a small hand with a large thumb splayed off toward the back of the track. These nimble paws, along with a semi-prehensile tail, allow the opossum to excel at tree climbing. They are agile climbers that use their tail as a brace or extra “hand” when climbing. A young opossum might be able to briefly hang by its tail, but an adult is too heavy for this feat.

The opossum is a wanderer in search of food to scavenge. Even carrying young, a female opossum may use multiple burrows. Human development and global warming have only encouraged the opossum to spread its range and develop an even greater stronghold in the animal kingdom.

If you Google the word “opossum,” you are likely to find a host of pest-control companies that specialize in ridding your home of these strange nocturnal creatures. But the fact is that the opossum gets along just fine in almost any environment and thrives anywhere it can find a decent water source and a few places to hide during the daylight hours.

The opossum does not have strong claws for digging home burrows. It relies on burrows abandoned by other animals for its multiple temporary homes. A cat door to your garage is a welcome entryway to a warm place to spend the winter. Opossums have hairless ears, feet and tails and cannot tolerate extreme cold. Indeed, they are subject to frostbite if exposed to a harsh winter climate without adequate shelter.

The diet of the opossum is virtually anything it can scavenge. Carrion is a standard mainstay of the diet. Quite often, our encounters with opossums occur when we see them in our car headlights as they scavenge road kills. They eat the entire animal, including the bones. Troubled by roaches, grubs and snails in your yard? The opossum will eat them. The opossum will eat anything that you might leave out in the yard; composted garbage, birdseed, overripe fruit, suet cakes and cat food are some of its favored treats. The opossum is also very happy to eat any and all snakes. It is immune to the venom of copperheads, water moccasins and rattlesnakes. In the southern part of its range, these snakes are a regular part of opossum diet.

Many people consider opossums to be stupid, but they have an incredible memory for relocating food sources. They do not rely on learned behaviors, but they are blessed with many innate hardwired behaviors than ensure their survival. The opossum is born with the ability to find exactly what it needs to survive in close proximity to humans, along with a keen sense of smell and a robust immune system.

Worried about a rabid opossum attacking your pets or children? Don’t fret – the opossum is highly resistant to rabies, as its body temperature is lower than that of most mammals. The opossum is also resistant to distemper. Besides, opossums simply don’t attack. When we talk about the opossum, we are talking about one of nature’s most resilient and passive animals. It does not avoid death by snakebite or rabies due to its lightening-fast reflexes, but by its strongly developed immune system.

When attacked, the opossum will stand still and face you with its mouth agape, showing all 50 of its very sharp teeth. This toothsome display is fearsome but rarely dangerous, as opossums avoid confrontations. In just about any situation, the opossum will lose a fight with a dog. They don’t run very fast and have a somewhat clumsy, flat-footed gait.

The hind foot of the Virginia opossum with its opposable thumb-like hallux. Photo by Mary Parker Sonis

This brings us to the other of the opossum’s passive defenses – playing possum. When a predator has cornered or captured an opossum, the poor animal can involuntarily fall into a catatonic state involving total paralysis, lowered heart rate and the release of a foul-smelling secretion from its anal glands. A dead animal is no fun for a predator to chase, and with any luck, the dog or coyote might release the opossum and look for something else to eat.

This near-comatose state can last for hours. In one instance, a person encountered an opossum that the family dog had killed. The homeowner tied the dead opossum in a plastic bag and threw it in his trashcan. The next day, a very-much-alive opossum was found to have chewed its way out of the bag and gone on to dine on the contents of the bin.

For all this resilience, the opossum has a very short life. It is estimated that more than 8 million opossums are killed by cars every year. Remember that the opossum will stand still when threatened, and it has never learned to run from cars. It is a short life for animals that eat in the fast lane. They are predated upon by dogs, coyotes, foxes and owls. The lifespan of the opossum in the wild is rarely longer than three years.

The opossum won’t damage your garden or tear up your lawn, but it will happily take up residence in your crawlspace or raise its young in your attic if it can find a way to enter your very comfortable house. Hang a full bird feeder, and you can guarantee a fine life for this little forest intruder.