By Calvin Abbott
There are probably few people in the Bay Area who aren’t aware of opossums, but in talking to people recently I realized there are also few people who know much more than what they look like, or that they like to be in trees. Where I live in Richmond, opossums are in a category I like to think of as uncommon and omnipresent. I never see a lot of opossums at once, I don’t see them every day or even every week, but it is also not surprising when one does show up in one of my fruit trees, or curled up in the hay in my garden. What was surprising, however, was when my cat carried an opossum through his cat door, and walked up to me and dropped it at my feet. In so doing my cat forced me to look into a fascinating animal I had been overlooking my whole life.
This opossum, like all others in the Bay Area, US and Canada is a Virginia Opossum (Didelphis virginiana). At first glance you may assume this little critter is a kind of rat, but not only is it not a rat, it’s not even a rodent. Opossums are the only native marsupial in the aforementioned habitat range. It is however not native to that entire range, its territory on the west coast is fairly new, dating back as recently as the 1930s. It is believed that it was brought from the east coast to the west coast as a food source during the Great Depression. Much of it’s northern creep into Canada is new as well, and is speculated to be enabled by warming temperatures caused by global climate change.
Humans share their relatively new urban environments with a number of species, and such cohabitation does carry with it some degree of risk. On that scale of risk I believe, and most experts would agree, opossums fall on the net beneficial side. Cases of an opossum biting a human are exceedingly rare, as are the chances of that opossum carrying a disease like rabies that can be transmitted by an animal (though of course if an opossum or indeed any wild animal bites you should go to the hospital). Opossums can carry diseases in their secretions, but avoid handling them and you have little to worry about.
The benefits of opossums for humans are numerous, as they do a marvelous job of pest control. They eat ticks, beetles, snails, mice, rats, and even venomous snakes, not only helping deal with garden pests but also animals that pose a more substantial threat to humans. They also have a penchant for eating fallen and rotting fruit, while generally leaving healthy plants alone, which can help keep our outdoor spaces cleaner and our plants disease free.
While I am not a person who believes every animal’s existence should have to be justified by their cost/benefit analysis to humans, I do hope that some of the harder convinced among us can come to realize that these animals are helpers not pests, and maybe next time you see one you will let it go on its way.
Walsh, L. L.; Tucker, P. K. (2017). “Contemporary range expansion of the Virginia opossum (Didelphis virginiana) impacted by humans and snow cover”. Canadian Journal of Zoology. 96 (2): 107–115. doi:10.1139/cjz-2017-0071. hdl:1807/81311.