Opossums

The Virginia Opossum (Didelphis virginianus) is the only marsupial native to North America; however, they are not native to the western United States. Known simply as “possums,” they originally lived only in the southeastern United States and Central America. Virginia Opossums were introduced to the West in 1890 and currently have established populations along the West Coast from British Columbia to San Diego.

Due to the lack of natural predators, hunting and an abundance of food and shelter, opossums have adapted to living among humans and they now occupy most human-occupied habitats in western Washington.

Opossums are very primitive mammals that have been around since the time of the dinosaurs and have changed little since then. They are very slow to react to headlights, other animals and even people because their primitive brains process information very slowly. But this by no means makes them unintelligent. In fact, new studies suggest they rank above dogs and are almost on par with pigs in intelligence.

Did you know? Opossums rarely become sick with rabies or other wildlife diseases.

 

Description

Virginia Opossums are about the size of a small dog, their fur generally appears grayish but they can be black, cinnamon and even albino. They have dark colored feet, a whitish face, naked ears and a hairless tail. Virginia Opossums have 50 teeth, the most of any North American mammal.

Did you know? Opossums use their tails to brace themselves while climbing trees.

 

Ecology

Habitat

Opossums live in forested or brushy habitats, but they have adapted well to living close to people in cities and suburbs.

Dens

Opossums will den nearly anywhere that is dry, sheltered and safe. This includes burrows dug by other mammals, rock crevices, hollow stumps, wood piles and spaces under buildings. They fill their dens with dried leaves, grass and other insulating materials. Opossums have several active dens they move between to avoid predators.

 

Development and Family Structure

Like other marsupials, opossums give birth to almost embryonic young. The newborns crawl into their mother’s pouch, where they remain firmly attached to a nipple until they are about 50 days old. When the pouch becomes too crowded at 80 to 90 days, the joeys venture out to ride on their mothers’ backs. At a little over three and a half months old, the young opossums start to leave their mother and venture out on their own.

 

Foraging

Opossums are omnivores; they eat just about anything including fruits, nuts, grains, insects, slugs, snakes, frogs, birds, eggs, shellfish, mice and carrion.

Did you know? Opossums have very little body fat and they do not store food; therefore, they must forage year-round.

 

Behavior

Basically solitary, opossums avoid one another except during the breeding season in late winter. They are generally nocturnal and they spend the day in hollow tree trunks, rock crevices, under brush piles, or in burrows.

They are excellent climbers and good swimmers. Opossums also spend a lot of time slowly ambling about on the ground, and as a result they are frequently struck by cars. They have an excellent memory and a very sensitive nose; enabling them to find and remember where food is. When facing danger, they “play possum,” entering a state similar to fainting that can last from less than a minute to six hours. The maneuver is designed to make predators lose interest.

Did you know? The act of playing possum is an involuntary response to predators.

 

Living with Virginia Opossums

Although opossums sometimes overturn garbage, eat fruit or vegetables from the garden, and occasionally get into a chicken house, they don’t do much harm. They can easily be discouraged through habitat modification.

Remove attractants

Food scraps in garbage and compost attract opossums. Dispose of trash in a metal can with a tight-fitting lid. Further secure it with a bungee cord or chain. Do not put food of any kind in open compost piles; bury food waste underground or use a lidded worm box.

Opossums are also drawn to pet food. It is best not to feed cats and dogs outside, but if you have no other choice, pick up bowls, leftovers and spilled food as soon as your pets have finished eating. Do not leave bowls or food scraps outside at night. To prevent opossums from entering through pet doors, do not put food near the door and lock the flap at night.

Exclusion techniques

Opossums look for convenient denning sites, which include rock, wood and brush piles, and spaces under porches, houses and sheds. Before sealing possible den sites or entries, be sure there are no opossums inside, especially young who are mobile but not yet independent. To determine if there are animals present, you can cover openings near the ground with loose soil and watch to see if an opossum digs out.

If you suspect activity by an adult in a crawl space or opening in a wall, begin exclusion by sealing all but one available entry. Fit the one hole with a one-way door with a hinged flap so that the opossums can escape but not re-enter.

Leave the door in place for several days while you continue to watch for activity. Once you are certain all opossums have left, close all openings with boards or metal screening, making sure that the barrier extends eight to 10 inches underground. Remove other potential cover such as debris piles and low-growing vegetation.

If you keep chickens, it is best to prevent opossum predation by enclosing the coop at night. Make certain that the coop has well-fitting doors and a solid concrete floor. To prevent opossums from digging in, surround the coop with fencing that extends six to eight inches underground.

 

References

Burke Museum. January 6, 2016. Mammals of Washington: Didelphimorphia.

Feldhamer G.A., Thompson B.C. & Chapman J.A. (Eds). (2003). Wild Mammals of North America, Biology, Management, and Conservation (2nd ed.). Baltimore MD: The Johns Hopkins University Press.

Washington Department of Fish and Wildlife. January 5, 2016. Living with Wildlife: Opossums.