Imagine you’re being attacked by a ferocious predator.
With no chance of escape, you do what any courageous, self-respecting possum would do: curl into an immobile state called catatonia, stick out your tongue, drool, and ooze some foul-smelling liquid from your anal glands.
Disgusted, your assailant loosens its grip, decides you’re not the dinner it was looking for, and departs. After 10 minutes, you resurrect and merrily saunter on.
From lemurs to lizards, ants to amphibians, sharks to chickens, hundreds of animals “play dead” as a survival tactic. Nicknamed “playing possum” after its star performer, feigning death is also called ‘thanatosis’. That’s from Thanatos, the ancient Greek deity of death. But most scientists call it tonic immobility, or TI. How and why TI occurs depends on the species and situation.
Most of the physiological mechanisms underlying these theatrics originate in the parasympathetic nervous system, better known for controlling cycles of resting and digesting. In possums, the parasympathetic nervous system causes their heart rates to drop by nearly half, respiration by a third, and body temperatures by more than half a degree Celsius for up to an hour.
But maintaining a death ruse isn’t easy. The performers are constantly gauging their surroundings for cues on when it’s safe to rise. So TI can work to an animal’s advantage, unless someone else knows its secret. Would you believe that California orcas can flip over young great white sharks, inducing TI for so long the immobilized sharks, who must move to respire, essentially suffocate.
For more surprising stories of animal fake-outs, check out the TED-Ed Lesson The surprising reasons animals play dead – Tierney Thys
Animation by Stretch Films