MISSOULA - It's been a staple of wildlife documentaries and social media alike — the opossum, seemingly lifeless, sprawled out on the ground.
It's just a classic case of “playing possum”. But contrary to popular belief, opossums aren't staging a dramatic play of their own demise, instead they enter a state called "tonic immobility" which is a physiological response to extreme stress.
They have no conscious control over this. It's like they're slipping into a stress-induced snooze session. The possum's heart rate slows down, breathing becomes shallow, and they obviously look dead.
Biologists believe this response is linked to a predator's instinct to release prey that's seemingly lifeless — kind of like a "yuck, this isn't appetizing anymore" reaction. In a similar perspective if you are threatened by a grizzly bear you are supposed to “play dead” by laying flat on your stomach with your hands clasped behind your neck to get them uninterested.
When a possum becomes involuntarily immobilized it can take them anywhere from a few minutes to a few hours to start moving again.
A publication in Clinical Autonomic Research hypothesized that our ancestors may have had a similar response to threats during Paleolithic times — developing a fainting response to fear as a survival strategy. Fainting triggered by fear-circuitry activation had an evolutionary advantage in a similar way of trying not to get eaten by appearing dead.
Although possums seem like some kind of mutated rat, they’re pretty unique animals and are the only marsupials found in the U.S. They’re also really good at eating ticks. Researchers at the Cary Institute for Ecosystem Studies discovered that opossums can eat as many as 5,000 ticks during one season which can help slow the spread of Lyme disease.
They also could be the key to saving you from a deadly snake bite. In a fascinating twist, these creatures boast immunity to the venom of almost every snake inhabiting their natural territory — yes, that includes even rattlesnakes — with the sole exception being the elusive coral snake.
And if that’s not amazing on its own, possums also rarely get rabies. As marsupials, possums have a lower body temperature than most other mammals, so their bodies don’t provide a habitable environment for the virus.
We have gone back and forth calling them opossums and possums. Here in the U.S., opossum and possum describe the same animal, and both pronunciations are accepted. But if you're across the globe in Australia, using the shortened word possum refers to a completely different order of animals.
So next time you come across an opossum sprawled out on the ground, remember, it's not auditioning for the latest possum soap opera, but it’s just having a moment.
