- This “Good Natured” article is written and submitted to Kane County Connects by Pam Otto, the manager of nature programs and interpretive services at the Hickory Knolls Discovery Center, a facility of the St. Charles Park District. She can be reached at 630-513-4346 or email@example.com.
I spoke with a woman the other day who was calling to report an opossum feasting on the fallen seeds beneath her birdfeeder. Her vivid description reminded me of how genuinely poorly opossums are adapted to our northern Illinois climate, where temperatures are — or at least used to be — quite chilly at this time of year. Naked ears, naked tail, and a naturally low body temperature of 94 to 97 degrees — none of these features do opossums any favors when the thermometer dips below freezing.
Add to that the fact that opossums do not hibernate, and you end up with a mammal that seems destined to fail.
But then I remembered the fact that the opossum, Didelphis virginiana, exists today in pretty much the same form its ancestors displayed 65 million years ago.
That’s right, that chunky, clunky little critter you see pottering around your neighborhood on garbage night has roots that go back 65 million years.
Scientists poking around in limestone deposits in Wyoming’s White River Badlands a few years back discovered a skull they say belongs the forebear of the opossums we have today. Even more remarkable, their depiction of the ancient Mimoperadectes houdei looks an awful lot like our own Didelphis virginiana.
Clearly, opossums had the good fortune to, early on, develop a set of behaviors and adaptations that literally have withstood the test of time. For one, they can and will eat almost anything. Invertebrates like worms and insects might make up one meal, pet food the next, then a frog or berries for dinner and garbage for dessert.
Opossums also breed rapidly and give birth to large litters. Twenty-plus young at a time are possible, although most litters average eight or nine. Here in Illinois, breeding occurs twice a year, so their reproductive capacity is high.
And as marsupials — the only marsupial native to North America, incidentally — their young are born just 13 days after conception. These teensy creatures, weighing just 0.0056 ounces each, creep into mom’s pouch, where they are relatively protected, and stay for anywhere from 60 to 100 days. Upon leaving the pouch, they may hitch a ride on mom’s back for a couple more weeks, further extending the benefit of parental protection.
Another advantage opossums can claim is their ability to call just about anywhere home. Wooded areas are preferred, but shrubby fencerows work fine too. As do attics, garages those dark spaces under sheds and decks, and basements. (Just ask my dad about that last one.)
Although mostly terrestrial, opossums can from time to time be spotted hanging out in trees—though not by their tails, as is often rumored. Yes, their tails are weakly prehensile and can curl around objects, but they just aren’t strong enough to support the animal’s entire body weight. Besides, opossums have another really cool adaptation for moving about the branches—opposable thumbs on their rear feet.
Despite these many fine qualities, opossums often are labeled as “dumb.” Sure, they’re slow and lumbering, and their defensive displays rarely pass beyond teeth-baring and hissing. Their well-known trick of “playing possum” (which actually is instinctive and not controllable) also makes them look like pushovers.
It doesn’t help that their brain is pretty small relative to their body size. (An opossum’s brain cavity holds 25 beans, a cat’s 125.) Even so, when scientists tested the opossum’s intelligence using the ever-popular run-through-a-maze method, our marsupial friend actually performed better than its cat and rat competition.
One thing individual opossums don’t have going for them is longevity. Fewer than 10 percent survive their first year, and an opossum of two or three years of age is an elder indeed. The group as a whole, though, has had what it takes to survive 65 million years on this planet. And, who knows? They may be around 65 million more.