Why do opossums act dead?

Playing possum is a term we have all heard of. But do you know it is a trick played by opossums to protect themselves? Let’s find out.

A possum playing dead.

Possums or opossums are unique animals found in the Americas. Though they resemble rodents such as rats, with their long hairless tails and whiskered snouts, scientifically, they are classified as marsupials. They are, in fact, the only kind of marsupials found in the U.S., located mostly around the State of Virginia. Like other marsupials, female possums carry their young ones in their little pouches.

Possums do not grow very big, with an average weight of about 7kg. But they move very slowly and are peaceful animals that prefer to run away or hide from fights.Evolution has made this creature immune to snake venom, a rare feat, but still, they are vulnerable to attacks by other predators - including dogs, coyotes, foxes, and sometimes even humans. As a result, possums have developed a unique survival strategy - to play dead.

When the opossum plays “possum”, they are not playing at all! In fact, they just cannot get up until the perceived danger is gone. The prospect of facing danger sends the animal into a seizure or temporary shock that is out of their control. The experience will induce the opossum to go into a state of coma that may last for between 40 minutes or more than 3 hours.

Going into this state of shock will cause the opossum’s body to go limp state while the heartbeat slows down. They grind their teeth in a crouched position, sticking their tongues out. They emit a smell like their body is decaying. They also exhibit symptoms of rigor mortis. Predators might play around the body for a while but will leave eventually thinking the creature is dead. This ‘playing dead’ is regarded as an instinctive defense response known as thanatosis.

Thanatosis is distinct from “freezing” which many living beings do, to keep quiet and hide when a predator approaches. But once detected, they are ready and able to move. In thanatosis, the body just cannot move. Many scientists refer to this phenomenon as “tonic immobility”, where there is a prolonged contraction of muscles. Not only possums, but many other reptiles experience tonic immobility including the hognose snake, pygmy grasshoppers, birds, and bees. Sometimes, humans can experience it too, when confronted with life-threatening situations.

FUN FACT

Possum and opossum refer to the same animal in the US and to the rest of the world except for in Australia, where possum refers to another species.