Featured Animal: Opossum

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​Virginia Opossum

(North American Opossum)

Didelphis virginiana

The opossum is one of Earth’s oldest mammal species—its evolution reaches back to the extinction of the dinosaurs.

Wherever you live in Iowa, you have a good chance to see these ancient natives. Their natural habitat includes woodlands, swamps, and streams, but they are also common in urban areas due to their opportunistic behavior. Opossums den up in wood or brush piles, hollow trees, rock crevices, or buildings.

Some say the opossum looks like a large rat. With its pointed face and long hairless tail, we cannot deny there is some resemblance, but this critter is not a rodent. The opossum is a marsupial, and the only one in North America. 

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Marsupials are animals with an external pouch where they raise their young. No bigger than a dime, opossums are born in an embryonic state. The young crawl across their mother’s stomach and find their way into the pouch; however, there are only thirteen teats. Litters can be larger than thirteen, but only thirteen young can be protected and fed. 

Babies, called joeys, are ready to leave the pouch at around three months. The mouse-sized babies crawl to their mother’s back where they cling for four to six weeks. When mothers are out and about, young can fall off too early and get left behind. Echo Gard, a licensed wildlife rehabilitator and president of Guardians of Rescue and Rehabilitation, receives frequent calls regarding opossum young, especially in the spring. She says they are ready to be on their own if they are eight to nine inches from the tip of the nose to the tip of the tail.

Adult opossums are about the size of a large domestic cat. Coloring varies somewhat, but all individuals have long hair ranging from white to dark grey. Their noses, ears, tails, and feet are hairless, and their back paws have opposable thumbs, allowing them to manipulate objects and climb trees. 

Though young may hang from trees with their prehensile tails, the adults are much too heavy for that. Their tails are incredibly useful though. Adults will use them to haul soft materials like leaves or straw into their dens.

Opossums have many unique defensive characteristics and behaviors:

• They are immune to rattlesnake and copperhead venom.

• When threatened, they may open their mouths wide and bare their teeth. This can be a bit intimidating as opossums have fifty—more teeth than any other Native American animal.  

• Other defensive behaviors include hissing, drooling, and swaying. These actions are often interpreted as a sign of rabies; however, due to their low body temperature, opossums are resistant to the virus.

• They sometimes “play dead” for up to several hours as a last resort. More research is necessary to determine whether this is intentional or involuntary, but during this fully conscious state their mouths fall open, their tongues hang out, and they emit feces or liquid, simulating death.

Despite their many creative defensive maneuvers, opossums are gentle creatures. If domestic cats are fed outside, opossums can be seen dining right alongside them. If spotted by humans, they will likely toddle away rather than protest.

Though opossums are mostly nocturnal, they can be seen during the day. Since their feet, noses, and tails are hairless, winter months are especially hard on them. They do not hibernate, but extreme cold will cause them to stay in their dens to protect themselves from frostbite. The sun may coax them to soak up some warmth while hunting for food. Opossums are common visitors underneath a well-stocked bird feeder.

All Iowa natives are beneficial to the ecosystem. Though often touted as voracious tick-eaters, ticks are not a major part of an opossum’s diet. However, they play many important roles in natural and urban areas. Opossums balance the population of skunks and raccoons by competing for many of the same foods. They dine on garden pests like snails and slugs, enjoy snakes, mice, rats, and insects, scavenge overripe berries, and clean up carrion. Opossums are also prey for other Iowa natives: raptors, coyotes, foxes, and bobcats.

Echo Gard recommends if you find a joey or an injured adult, don’t attempt to feed it. If an opossum’s body temperature is too low or they are severely dehydrated, they cannot digest food. Cow’s milk is especially problematic for wild animals and should never be offered. These actions can lead to organ failure and death. Gard recommends keeping them in a warm, quiet place. A heating pad underneath a blanket is ideal. Call a rehabilitator as soon as possible. Licensed individuals can be found by county via Iowa State University Extension and Outreach and the Iowa Department of Natural Resources.

Humans are not separate from nature—we are nature. Our most important lessons are modeled by the animals and plants that contribute to our living landscapes. If opossum has wandered into your life today, observe and learn from one of Iowa’s oldest living mammals.