Opossums

The Virginia Opossum is the only marsupial (pouched mammal) native to North America. Also known simply as "possums," they originally lived only in the southeastern United States. Opossums were introduced to the West in 1890 and currently have established populations along the West Coast from British Columbia to San Diego.

Generally nocturnal, opossums spend the day in hollow tree trunks, rock crevices, under brush piles, or in burrows. Because of their long, naked tails, opossums are sometimes mistaken for large rats. Their long teeth give them a menacing look, but opossums are actually quite docile and prefer to avoid human contact.

Opossums live in forested or brushy habitats, but they have adapted well to living close to people in cities and suburbs. They are excellent climbers and good swimmers. Opossums also spend a lot of time slowly ambling about on the ground. Sadly, as a result, they are frequently struck by cars. When facing danger, they also do "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.

Diet and breeding

Opossums are omnivores. They eat both plant and animals and scavenge carrion and garbage. Basically solitary, opossums avoid each other except during breeding season in late winter.

Like other marsupials, opossums give birth to almost embryonic young. The newborns crawl into their mothers' pouches, where they will remain firmly attached to a nipple until they are about 50 days old. When the pouch becomes too crowded, the young venture out to ride on their mothers' backs.

Solving and preventing conflicts

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.

Removing 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. (Read more about composting from Seattle Tilth.)

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 8 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 6 to 8 inches underground.