Opossums

The opossum (Virginia opossum, Didelphis virginiana) is a cat-sized, gray, nocturnal marsupial with a white face and a long naked tail, and it's the only marsupial in the US and Canada. It's a harmless scavenger that rarely carries rabies; the problems it causes are raided trash, eaten pet food and dens under decks and sheds.

Most people meet one at night, frozen in the headlights or hissing from under the porch. Here's how to identify it, what it eats, what its babies and droppings look like, and when it's actually a problem.

Possum vs opossum

This is the most searched opossum question. Both words are used in the US, and both mean the same animal in your backyard.

• Opossum is the correct name for the American animals (order Didelphimorphia, about 100 species from Canada to Argentina). The only one north of Mexico is the Virginia opossum.
• Possum, in biology, refers to a separate group of marsupials in Australia and New Guinea (brushtail, ringtail and others). They look different: furry tails, rounder faces, tree-dwelling.
• In everyday American speech "possum" is just a shortened "opossum", as in "playing possum".

So "is it a possum or opossum?" In the US, technically opossum, and nobody will misunderstand you either way.

How to identify a Virginia opossum

• Size: like a large house cat, 24-40 inches including a 10-20 inch tail; 4-14 pounds. Males are larger.
• Fur: grizzled gray-white (darker, almost black forms occur in the South), coarse guard hairs over a soft underfur.
• Face: long, pointed, white, with a pink nose and black, hairless, rounded ears often pale-tipped.
• Tail: long, scaly and mostly naked, which leads people to think "giant rat". It is prehensile and helps with climbing and carrying nesting material.
• Feet: five toes on each foot; the hind foot has an opposable, clawless "thumb". Tracks look like small star-shaped hands.

Opossum teeth: 50 of them, more than any other North American land mammal. The wide open-mouthed hiss that shows all of them is a bluff.

Opossum skull: long and narrow with a prominent crest along the top and that full row of small, sharp teeth, which is why opossum skulls are a favorite of bone collectors.

Look-alikes

• Rats have similar naked tails but are much smaller (a Norway rat is under 1 pound) and brown.
• Raccoons have a black mask and ringed, furry tails.
• Skunks are black with white stripes or spots and fluffy tails.

Behavior and diet

Opossums are solitary and nocturnal. They don't dig their own burrows or keep a permanent home. They move every few days between dens: under decks, porches and sheds, in brush piles, hollow logs, crawl spaces, attics and garages.

Opossum diet: almost anything. Insects, worms, snails and slugs, mice, frogs, carrion (including road kill), bird eggs, fruit and berries, garden vegetables, compost, garbage, and pet food left outside. They're often credited with eating thousands of ticks a season; that figure comes from a lab study and later field work hasn't confirmed it, but they do eat ticks along with lots of other invertebrates.

They don't hibernate. In northern states they stay in dens during the coldest spells, and frostbitten ears and tail tips are common.

When threatened they first hiss, growl and drool. If that fails, some "play possum": an involuntary faint where the animal goes limp, lies on its side with tongue out, and releases a foul fluid from the anal glands.

Baby opossums

Breeding runs from about January to July, with one to three litters a year in the South and one or two in the North.

• Pregnancy lasts only about 12-13 days. Newborns are the size of a honeybee and crawl into the pouch.
• The mother has 13 teats; extra young don't survive.
• Babies stay in the pouch about 2 months, then ride on her back for several more weeks.
• They're independent at about 3-4 months and roughly 7 inches long not counting the tail.

Found a baby opossum? If it's 7 inches or longer (body only), it's independent: leave it. If it's smaller and alone, or the mother was hit by a car (babies can survive in her pouch), call a licensed wildlife rehabilitator. Wear gloves if you must move it.

Opossum lifespan

Short. Most wild opossums live 1-2 years; cars, dogs, owls, coyotes and winter weather take most of them. Captive animals reach 3-4 years. They age fast, which is part of why they breed so heavily.

Are opossums dangerous?

Opossum rabies is very rare. Their low body temperature (about 94-97 °F) seems to make them poor hosts for the virus. Still, any mammal can get rabies; a bite needs washing with soap and water and a call to your doctor or health department.

Other concerns:

• Bites: only if cornered or grabbed. They want to escape.
• Fleas and ticks: opossums carry cat fleas and ticks and can bring them close to the house; see fleas.
• Leptospirosis, salmonella and other bacteria in droppings and urine.
• Equine protozoal myeloencephalitis (EPM): opossum feces can spread a parasite that seriously affects horses, so keep them out of feed and barns.

Opossum poop

Opossum droppings are 1-2 inches long, about 3/4 inch wide, smooth-sided and often curled at the end, like a small dog's. Older ones may have white or yellow mold. They contain seeds, fur, bones or insect shells. You'll find them under decks, in garages and near the trash, wherever they eat and rest. Raccoons, by contrast, use a shared latrine; see raccoon for why that matters.

Clean with gloves and a disinfectant, don't sweep dry droppings, and wash your hands after.

Are opossums pests?

Mostly nuisance, rarely damaging. Typical complaints:

• Knocked-over trash cans and torn garbage bags
• Eaten cat or dog food on the porch
• Raided chicken coops (eggs and occasionally chicks)
• Eaten tomatoes, strawberries and fallen fruit
• Dens under porches, sheds and in crawl spaces or attics, sometimes with a smell if one dies there

Because they move on every few days, a single opossum often leaves by itself once food is removed. To make that happen faster, see how to get rid of opossums.

When to call a pro

Call a wildlife control operator if an opossum is inside the living area, in an attic or wall you can't reach, a mother with young is denning under the house, or one has died in a crawl space. Most states regulate trapping and relocating wildlife, so a licensed operator also saves you from legal trouble.