Myth has it that you can disarm an alligator by rubbing its belly. Some people don’t necessarily focus on the logistics of getting that close to the creature (let’s keep in mind the stomach is awfully close to all of those sharp teeth). However, we’re here to tell you that, yes, this is technically true—and alligators aren’t the only animals associated with this behavior.
“Belly rubbing refers to tonic immobility,” the National’s Zoo’s Sean Henderson told The Washington Post in 2008. “It’s a state of hypnotism generated by flipping the animal on its back and fully extending its neck” and, as we mentioned, stroking its belly. Fair warning, Henderson added: “Tonic immobility is generally brought about in an animal that is under heavily stressful conditions. Don’t try this at home!”
According to Isaac Marks’s Fears, Phobias and Rituals: Panic, Anxiety, and Their Disorders, tonic immobility refers to the “prolonged stillness and decreased responsivity in a previously active animal in the face of threatening stimulation.” This state can last anywhere from 15 seconds to several hours, although the average length falls around eight to 10 minutes in chickens. (Yep, they can be affected too!)
Sharks are another type of creature susceptible to tonic immobility. There seem to be two different ways to trigger this effect in sharks, the most effective way being by rubbing a shark’s nose. While the exact reason why this works is unknown, one ecologist writes “[an] untested possibility is that a shark’s electroreceptors are concentrated in the snout area, and perhaps overstimulating this area ‘shocks’ them into immobility.”
Another means of immobilizing a shark is to invert it, flipping it on its back. WIRED recounted an especially odd occurrence of a shark being put into a state of tonic immobility—by another animal:
“In 1997, eyewitnesses watched a female orca off the coast of California seemingly induce tonic immobility purposely in a great white shark. The orca held the shark upside down, inducing tonic immobility, and kept the shark still for 15 minutes, which caused it to suffocate to death.”
Remember when we mentioned that tonic immobility occurs in chickens, too? WIRED theorizes that it’s a defense mechanism for the birds. “You can lay it on its side, tuck its head under its wing and gently rock it, or put it on its back and stroke its sternum,” the site reports. “You can wave your finger in front of its face—starting with your finger close to its beak and then pulling your finger slowly straight back. The chicken will focus on your finger.”
Tonic immobility affects different animals in different ways. “I’ve observed alpacas and llamas ‘calmed’ into a state of relaxation by gently rubbing the upper gum just beneath the cleft in the upper lip,” veterinary surgeon David Anderson told the Cincinnati Enquirer. “The animals stop resisting being held, and stop vocalizing.”