Opossums

A marsupial is a mammal with young that are born not fully developed and are subsequently carried in a pouch on the abdomen of the mother where the young can attach to a teat and complete their development.  The most well-known animals in this group are kangaroos, but we also have one species in Illinois, the Virginia opossum, Didelphis virginiana.  The opossum is native to Illinois and is common in all parts of the state.  The oldest remains found in Illinois date back 100,000 years ago, while worldwide, opossums are one of the oldest known mammals, with remains dating back about 20 million years ago to the Miocene period.

An adult opossum has coarse gray hair covering its body with white facial hair and a long, pointed snout with a pink nose.  They are about the size of a house cat with hairless ears and a one to two foot long hairless tail.  Their tails are prehensile, adapted for seizing, grasping, or holding, and used for balancing and climbing.  The hind feet have no claws, but do have an opposable toe used for climbing and grasping.  They can appear fearsome when baring their teeth, having fifty of them, more than any other land mammal.  They live in urban or edge habitats, finding shelter in old dens, rock crevices, hollow logs, and under wood or stone foundations.

Females give birth to one or two litters each year, the first in mid-winter and a possible second litter in early spring.  Young are born about two weeks after fertilization.  A newborn, the size of a bumblebee, must crawl to the mother’s pouch where it will attach to a nipple and stay attached for two to three months to complete its development.  Up to twenty young, called joeys, are born in each litter, but the female adult only has 13 teats and the remainder of the young do not survive.  Young are weaned at about three months.  Usually nocturnal and solitary animals, young will often strike out on their own but may return to the family group for the winter. 

Opossum are omnivores eating a wide variety of food including fruit, grain, seeds, pet food, garbage, carrion, eggs, insects, frogs and other small animals.  Ticks, found on many Illinois mammals, are a favorite food item.  It is estimated that an adult opossum consumes several thousand annually.  Opossum are scavengers, seed dispersers, and a control for small mammal and insect populations.  In turn, they are prey for larger birds and mammals. 

When threatened, an opossum may respond by hissing, growling, baring its teeth, or playing dead.  Playing dead, an autonomic response, occurs when the opossum faints.  They lay on the ground with lips drawn back, teeth bared, eyes half or fully closed, saliva drooling, and a foul-smelling liquid excreted from their anal gland.  Individuals can be poked, turned over or picked up and carried away with no response.  They will recover by slowly regaining consciousness after several minutes or up to four hours.  In the wild, their average life span is two years, and the leading cause of death is being hit by a vehicle. 

Opossum are protected under Illinois law as a furbearer.  Hunting licenses are available each year with no limits.  Permits may also be issued for nuisance animals that may be trapped for removal to another area.  Adults are often infested with parasites, but carry none that are known to affect humans.  They are rarely encountered or seen, but you may be able to observe them in the evening, especially under bird feeders or where pet food is left outside.