When I lived in San Francisco, our house wasn’t too far from Golden Gate Park. As a result, we’d occasionally receive visits from wildlife, mostly wily raccoons. One night, I went into the backyard, turned on the outdoor lights and was seriously startled to see a strange creature I’d never encountered before.

Perched on top of our fence was a large animal with a white face and gray body. It was rodent-like but way too big to be a rat — unless it was a R.O.U.S., for you “Princess Bride” fans. When I jumped at seeing this strange visitor, the animal responded with a hiss and showed a lot of teeth. I have to admit, I was a little freaked out but when I looked closely, I noticed it had a cute pink nose and was gripping the fence with opposable thumbs on both its front and back feet. It scampered off and neither of us were the worse for wear.

You’ve probably guessed by now that my surprise backyard guest was an opossum, a Virginia opossum to be exact. I knew little about them but am fascinated by these animals that are actually part of the marsupial family. Yes, koala bears and kangaroos are their cousins. Opossums are the only marsupial native to North America and they’re truly remarkable creatures.

Being marsupials, baby opossums are born small and underdeveloped. At birth, they make their way from the birth canal to their mother’s marsupium, or pouch, where they fasten themselves to a nipple and hold on for about two months. From the pouch, the babies transition to their mom’s back, where they’re carried for one to three months, before hopping off and learning to make their own way in the world.

Opossums are hugely beneficial to our ecosystem. (And no, you shouldn’t call them “possums”; possums are a different species of marsupial, and are native to Australia.) Opossums eat ticks, fleas and small rodents, helping to control those populations. They also eat snails, slugs and overripe fruits and vegetables, helping to keep our gardens healthy and tidy. They can even eat rattlesnakes — and, interestingly, are immune to their venom. They’re also extremely resistant to rabies.

But if you’re not quite as delighted as I am to receive a visit from an opossum, simply make your property less inviting to them: Don’t leave pet food outside at night — opossums are not above a free domestic pet meal — pick up fallen fruit and securely fasten garbage can lids. Although they rarely tip over garbage cans themselves, they’ll take advantage when another nocturnal animal such as a raccoon does.

It’s easy enough to get them to leave — usually a bright light will do the trick — but if they see you, they just might “play possum” by rolling over on their side and playing dead. If they do this, just leave them alone. They may lie there for an hour or more but eventually they’ll scurry away when it’s safe.

Playing dead is a surprisingly effective defense against predators, but it doesn’t work against vehicles on the road. WildCare reports that their wildlife hospital admits 100 opossums every year, and most are babies orphaned after their mother was hit by a car. That’s another reason to be extra vigilant when driving, especially at night, when many of our wildlife neighbors are out.

I like sharing the story of my first encounter with an opossum because I think it illustrates the fact that sometimes what we first think of as scary, weird or intrusive can turn out to be something interesting, beneficial and even cute!

Lisa Bloch is the marketing and communications director for Marin Humane, which contributes Tails of Marin and welcomes questions and comments. Visit marinhumane.org, find us on social media @marinhumane, or email lbloch@marinhumane.org.