A few years ago, our cat disappeared during the night. We were devastated by the loss of our beloved Teddy and blamed the nocturnal coyotes who live in the open space near our home. However, during a visit to the Animal Shelter, we were told that opossums, raccoons, and birds of prey are capable of killing cats. We quickly turned our anger on the opossum (Didelphis virginiana) who ran along our fence at night and taunted the dog. It was easy to hate such an animal; with their rodent-like snouts, beady black eyes, and thick, hairless prehensile tails.

Last week, I attended an excellent presentation by the Suisun Wildlife Center. They brought owls, snakes, a turtle, and an opossum as demonstration animals. The opossum was tame, having been hand-raised by humans, and was (almost) cute. The presenters did not believe opossums were capable of killing cats and extolled their virtues, which include eating slugs and snails. Suddenly, I felt guilty for hating a harmless animal!

So, which is true? Is the opossum a vile cat-killing predator, or a docile, garden-pest-removing friend? The truth is, the opossum is neither of these.

The opossum is a native of the eastern United States, and the only marsupial indigenous to this country. They are nocturnal omnivores and eat fruits, nuts, green plants, insects, snails, snakes, frogs, birds, and their eggs, as well as small mammals such as meadow voles, mice, and rats. The opossum will eat fresh meat or carrion and is often seen feeding on road kill. Opossums do not prey on cats or other larger mammals but will attack them if cornered, or if competing for food.

Opossums cause loss to home gardens by eating nuts, berries, fruits, and grapes. They eat pet food left outside and may raid compost bins. The animals carry a variety of diseases, including leptospirosis, tuberculosis, relapsing fever, tularemia, spotted fever, toxoplasmosis, coccidiosis, trichomoniasis, and Chagas disease. They may also be infested with fleas, ticks, mites, and lice; and are hosts for cat and dog fleas, and flea-borne typhus. 

There are several steps you can take to deter opossums from occupying your yard. Be aware that it is illegal to trap and relocate wild animals without permission from the State of California Department of Fish and Wildlife: https://nrm.dfg.ca.gov/FileHandler.ashx?DocumentID=45902. Here's what you can do:

• Cut back overgrown shrubbery and trim back trees that overhang rooftops at least 5 feet from the roof edge
• Remove fallen fruit
• Stack firewood tightly, leaving no gaps suitable for a den; store scrap lumber and other items about 18 inches off the ground
• Ensure garbage cans have tight-fitting lids
• Do not place food items or table scraps in your compost bin
• Remove pet food placed outdoors by nightfall
• Block access to areas under stairs, porches, decks, and buildings with 1/4–inch mesh hardware cloth – BE SURE THAT THE ANIMAL HAS VACATED THE AREA FIRST
• Use poultry wire around gardens
• Use electrically-charged wire near the top of the fence. Visit the University of California's Pest Note regarding raccoons for more information: http://ipm.ucanr.edu/PMG/PESTNOTES/pn74116.html
• Use a motion-activated sprinkler system
• Use light, and sound from a loud radio to annoy the animal at night

For more information about how to deter opossums from inhabiting your property, visit the University of California's Agriculture and Natural Resources website at http://ipm.ucanr.edu/PMG/PESTNOTES/pn74123.html