The Virginia opossum, North America’s only native marsupial, is widely recognized for a peculiar defense strategy often referred to as “playing possum.” This common phrase describes their remarkable ability to appear lifeless when threatened. Far from a conscious act of deception, this behavior is a deeply ingrained biological response.
The “Playing Possum” Response
Playing possum, known scientifically as thanatosis or tonic immobility, is not a voluntary choice but an involuntary physiological reaction. When an opossum experiences extreme fear or stress, its autonomic nervous system triggers this protective shutdown. This response is akin to an animal going into shock or a temporary coma, rendering it unresponsive to external stimuli.
During thanatosis, the opossum’s body undergoes changes designed to mimic death. The animal typically collapses onto its side, its body becoming rigid and its feet curling up. Its eyes may remain open, appearing glassy or fixed, or they might close. Breathing becomes extremely shallow, almost imperceptible, and the heart rate slows significantly.
The opossum may also drool excessively, and its tongue might loll out of its mouth. It also releases a foul-smelling, greenish fluid from its anal glands, which simulates the odor of decay. This combination of visual and olfactory cues aims to deter predators, as many prefer live prey. The state of thanatosis can last from 40 minutes to four hours, allowing time for a predator to lose interest and move away.
Encountering a Possum in This State
If you encounter an opossum exhibiting thanatosis, leave the animal undisturbed and provide it with ample space. This allows the opossum to recover from its involuntary state naturally. Approaching or attempting to handle the animal can prolong its feigned death response and cause further distress.
Opossums are docile creatures that prefer to avoid confrontation. They are not aggressive towards humans and will flee or display warning behaviors like hissing or baring their teeth before resorting to playing dead. This mechanism is a last resort when escape or intimidation fails.
Keep pets, especially dogs, away from an opossum in this state. While the opossum is unlikely to react, an inquisitive pet could prolong its stress or inadvertently injure it. Contact local animal control or a wildlife rehabilitator only if the opossum appears genuinely injured, is in an unsafe location, or shows clear signs of being deceased. Due to the convincing nature of thanatosis, it is best to observe from a distance, assuming the animal is alive until proven otherwise.