Opossums (Didelphis virginiana) are not rodents, but they are often confused as rodents. (They are marsupials – like kangaroos!) Opossums are grey, brown and white with a sharp pointed face and a long, scaled tail. Adult opossums are 2-3 feet long with the tail included and can weigh up to 15 lbs. If you have seen or heard of “a rat as big as a cat,” it was most likely an opossum.

Opossums are nocturnal (active at night), but may be seen during the day if they have been disturbed from their hiding place, or if they are sick or injured. They are rarely aggressive; however, they may fight with and injure outdoor pets. They also carry pathogens that cause a variety of diseases including leptospirosis, relapsing fever, spotted fever, toxoplasmosis, coccidiosis, trichomoniasis, and flea-borne typhus. They also carry a large number of fleas.

Opossums play “possum” when captured and can even lower their heart and breathing rate to appear dead. When frightened they may hiss and exude a greenish musk-like fluid that smells terrible. They prefer to run and hide, but will bite if cornered or grabbed. An opossum that appears to be dead should never be handled; it may suddenly wake up and bite or scratch!

Urban and suburban opossums often den under buildings and decks. They can be kept out by making sure crawl space vents are in good repair, closing up other entrances to your crawl space, and using hardware cloth to close areas under decks.

Opossums are omnivores, and will eat almost anything, including fruits and vegetables, insects, small reptiles and mammals, pet food, and garbage. You can help discourage them from visiting  your property by harvesting all fruits and vegetables promptly, keeping garbage and compost in closed containers, and bringing pet food in at night. If there is no food or shelter on your property, you may see opossums passing through at night but they will not stay.

If you care, don’t share. Wildlife do not require human food to survive, and feeding them can cause them to become aggressive and start attacking people, which means they may be euthanized. It may also cause their populations to swell to the point they begin to pass around painful diseases like mange. If you want to help wildlife, do not feed them.

Opossums are the only marsupial native to North America, but are not native to California. They were introduced to San Jose in 1910 and then spread throughout the state.

More information on dealing with nuisance opossums is available from the UC IPM program website.

Page last reviewed: December 28, 2023