Ode to the Opossum
Article by Jessica Warren, ANR Agent – Camden County
If you know me well, you know that there are some things that I enjoy talking/teaching about more than others. At the top of that list is wildlife – especially misunderstood wildlife. Today I have the pleasure of sharing about the humble opossum. The Virginia Opossum, commonly called a possum, is North America’s only native marsupial.
First, let’s clear this up. Is it possum or opossum? It’s opossum. Possums are a different species of marsupial that are native to Australia – and honestly, they’re cuter. Cuter maybe, but not as special. As I mentioned, the opossum is the only native marsupial in North America. It is one of earth’s oldest surviving mammals, in existence for at least 70 million years. It has a prehensile tail which it uses for grasping and wrapping, but it does not sleep hanging by its tail. Opossums have an opposable hallux – a clawless big toe that functions like a thumb. Opossums are roughly the size of a large housecat and usually weigh 4-6lbs with the males weighing slightly more than the females. Their total body length is around 3 feet with 1/3 of that being composed of their nearly hairless tail. Opossums have 50 teeth – more than any other land mammal in North America. Male opossums have a bifurcated (forked) penis and females have a bifurcated vagina and divided uterus. This unique male anatomy led to a belief by early colonists that males bred with females through their nostrils and the females then sneezed the offspring into their pouches. Needless to say, science has come a long way.
Opossums are immune to snake venom as well as honeybee and scorpion venom – and they’ll eat all of those biting and stinging critters. In fact, they’ll eat just about anything. They’re diet naturally consists of plants, fruits, seeds, insects, snails, mice, rats, snakes (including venomous snakes) and carrion. This in itself makes them pretty useful to have around. However, they, like most of us, are opportunistic and will gladly take a free meal if you leave pet food outdoors or don’t secure your bird food or garbage appropriately. They are important seed dispersers and do us a great service in controlling pest species as well as cleaning up carrion that could spread numerous pathogens.
Opossums are found east of the Rocky Mountains and on the West Coast. They are also found in Central America, British Columbia and Ontario. They live in a wide variety of habitats: deciduous forests, open woods, farmlands and urban areas, but prefer wooded areas near water. Opossums are not territorial but they do have a home range. Males have a home range of approximately 350 acres which can increase to 785 during breeding season, and females have a home range of about 160 acres.
Opossums choose sheltered locations for their den: hollows in trees or fallen logs, rock cavities, brush piles or burrows of other animals. They use their prehensile tail to gather and transport nesting materials such as leaves and grass to the den site. Opossums are nocturnal, but seeing one during the day is not a cause for alarm. They do not hibernate but they will nest for several days at a time during very cold weather to prevent frostbite to their ears, tail and toes.
Sexual maturity is reached in the first year of life and they begin breeding in late winter and early spring. In warmer climates opossums may produce 2-3 litters per year. The gestation period is only 12-13 days, after which honeybee-sized young crawl along a pathway licked by the mother from the genital opening to the pouch and attach to a teat. There are 13 teats and often more young than teats. Those that do not make it to the pouch or do not get a teat perish. The young remain attached to a teat for approximately 2 months. The average litter size in the pouch is 7-8 young which leave the pouch and climb onto the mother’s back at 3 months. When they fall off of mother’s back over time they are left to fend for themselves.
In the wild opossums may live 1.5-2 years. In captivity their life expectancy is 3-4 years. Predators include coyotes, dogs, bobcats, foxes, racoons, raptors and humans. Human caused mortality includes hunting, trapping and vehicle strikes (often when they’re cleaning up our roadkill).
Opossums are rarely aggressive but will hiss and show their teeth when threatened. When they are faced with a threat that they can’t escape, they play dead. Their body produces a chemical that causes a paralysis of the muscles – similar to fainting. Their body goes limp, saliva drips from their open mouth and their tongue hangs out. They also defecate and exude an unpleasant smelling oily green slime from their anal glands. This reaction can continue for hours and is effective in deterring predators. If you find an opossum that you believe is dead, the best thing to do is to move it to a quiet area out of danger where it can recover and go on its way.
Opossums are considered resistant to rabies and rarely carry distemper. They are being used to research new antivenoms for humans because of their immunity to pit viper, scorpion and bee venom. They are immune to toxins like botulism, and perform better than rats and cats at solving maze problems. However, what might be most interesting is their ability to help in the fight against tick vectored diseases. Opossums are very efficient groomers and studies show that they may kill up to 4000 ticks per week per individual. In addition, they don’t contract or carry Lyme Disease. As our climate warms we are seeing tick vectored diseases expand their ranges so every tool to help control tick populations is a win for public health.