When faced with danger, opossums exhibit a defense mechanism known as “playing dead.” This behavior is a genuine physiological response, scientifically known as thanatosis or tonic immobility. It allows these marsupials to deter potential threats.
The Opossum’s Unique Defense
When an opossum “plays dead,” its appearance is strikingly convincing. The animal typically collapses onto its side, becoming motionless and rigid. Its mouth may hang open, often with saliva foaming around it, and its tongue might turn bluish and dangle out. Its eyes remain open but appear glazed and unresponsive, contributing to the illusion of lifelessness.
The opossum may also release urine and feces, as well as a foul-smelling, greenish fluid from its anal glands. This pungent odor mimics the scent of decaying flesh, making the animal seem unappetizing to predators who generally prefer live or fresh prey. These physical and olfactory cues create a powerful deterrent, signaling the opossum is not a desirable meal.
The Biology Behind the Behavior
The “playing dead” response in opossums is not a conscious decision but an involuntary physiological reaction triggered by extreme fear or stress. It is controlled by the autonomic nervous system, similar to how humans might faint from fright. This built-in defense system activates when the opossum perceives an inescapable threat, causing a cascade of internal changes.
During this state, an opossum’s body undergoes significant physiological alterations. Its heart rate can decrease by 46%, and its respiratory rate may slow by 30%, becoming shallow and irregular. Body temperature also drops, and muscles stiffen, mimicking rigor mortis. Despite these profound changes, the opossum remains in a catatonic state, not truly unconscious, but aware of its surroundings.
This behavior serves as an effective anti-predator strategy. Many predators hunt moving, live prey and avoid carrion due to disease risk. By appearing dead and emitting a putrid smell, the opossum convinces predators to lose interest and move on.
What to Do When You See It
If you encounter an opossum exhibiting thanatosis, the most appropriate action is to leave the animal undisturbed and give it ample space. This catatonic state can last for a variable duration, typically ranging from a few minutes to several hours. The opossum will eventually recover on its own once it senses the danger has passed.
Do not touch or attempt to move an opossum that appears to be playing dead. Doing so can cause further stress or provoke a defensive reaction like biting or scratching. Keep pets, especially dogs, away from the opossum to prevent additional stress or harm. Allowing it to recover naturally ensures its safety and well-being.