Imagine you’re being attacked by a predator. With no way to escape, you do what any brave possum would do: you curl up, become completely still, stick out your tongue, drool, and release a foul-smelling liquid. Disgusted, the predator lets go, decides you’re not a tasty meal, and leaves. After a while, you recover and go on your way.
From lemurs to lizards, ants to amphibians, and sharks to chickens, many animals “play dead” to survive. This behavior is often called “playing possum” and is scientifically known as thanatosis, named after the Greek god of death. Most scientists refer to it as tonic immobility, or TI. The way TI is used can vary depending on the species and the situation. Animals often emit unpleasant odors and take on strange postures to enhance this survival tactic.
Some animals even sacrifice their neighbors to survive. For example, quail chicks that freeze while their siblings run around have a better chance of survival when a predator is near. In another example, mother cats can pinch the back of their kittens’ necks to induce a different kind of immobility called clipnosis, which keeps the kittens quiet and easy to carry.
The physiological mechanisms behind these behaviors mainly come from the parasympathetic nervous system, which controls resting and digesting activities. In possums, this system causes their heart rates to drop, breathing to slow, and body temperatures to lower for up to an hour. The neurotransmitter dopamine also plays a role; for instance, flour beetles with low dopamine levels tend to play dead more often than those with higher levels.
Maintaining the act of playing dead isn’t easy. Animals must constantly assess their surroundings to know when it’s safe to move again. Chickens, for example, can sense when a predator is watching them. Research shows that when a stuffed hawk was used in an experiment, chickens came out of their immobile state more quickly when the hawk’s eyes were turned away.
Some animals use TI for reasons other than defense. For example, the sleeper cichlid fish pretends to be a dead carcass to lure scavengers, which it then attacks. Additionally, some animals fake death as a mating strategy. Male nursery spiders offer silk-wrapped insects to females, who might eat the males. By playing dead while the female eats, these males can cautiously revive and increase their chances of mating.
While TI can be beneficial, it also has risks. For instance, California orcas can flip young great white sharks, causing TI for so long that the sharks, which need to move to breathe, suffocate. Humans can also induce TI in sharks by gently stroking their snouts and turning them over, which can last up to 15 minutes—enough time for researchers to insert tags, remove hooks, or perform surgeries. However, this technique can be risky as TI can hinder breathing and cause stress.
Humans can experience TI too, especially when freezing with fear during violent situations. Understanding this ancient, involuntary form of self-defense helps us comprehend why some people don’t flee or fight when faced with danger. Studying TI in animals not only reveals insights into their behaviors but also helps us understand our own responses to threats.
Imagine you are an animal that uses tonic immobility as a survival tactic. Choose an animal from the article and create a short skit demonstrating how it plays dead. Consider the environment, the predator, and the specific behaviors the animal uses. Perform your skit for the class and discuss the effectiveness of this strategy.
Conduct research on another animal not mentioned in the article that uses tonic immobility. Prepare a presentation that includes the animal’s habitat, predators, and how it uses TI to survive. Present your findings to the class, highlighting any unique adaptations the animal has developed.
Participate in a class debate on the risks and benefits of playing dead as a survival tactic. Divide into two groups, with one arguing that the benefits outweigh the risks and the other arguing the opposite. Use examples from the article and additional research to support your arguments.
Write a short story from the perspective of an animal using tonic immobility. Describe the situation leading up to the use of this tactic, the animal’s thoughts and feelings during the process, and the outcome. Share your story with the class and discuss the emotional and physiological aspects of playing dead.
Design a simple experiment to test the effectiveness of tonic immobility in a hypothetical animal. Outline the variables, controls, and methods you would use. Discuss how you would ensure the ethical treatment of animals in your experiment. Present your experimental design to the class and receive feedback.
Imagine you’re being attacked by a predator. With no chance of escape, you do what any courageous possum would do: curl into an immobile state called catatonia, stick out your tongue, drool, and release a foul-smelling liquid. Disgusted, your assailant loosens its grip, decides you’re not the meal it was looking for, and departs. After a short while, you recover and continue on your way.
From lemurs to lizards, ants to amphibians, sharks to chickens, many animals “play dead” as a survival tactic. This behavior, often referred to as “playing possum,” is also known as thanatosis, named after the ancient Greek deity of death. Most scientists refer to it as tonic immobility, or TI. The occurrence of TI varies depending on the species and situation. Emitting unpleasant odors and adopting unusual postures are common behaviors that play important roles in this tactic.
Some animals even sacrifice their neighbors: quail chicks that freeze while their kin run around have a better chance of survival when pursued by a predator. Speaking of predators, feline mothers can pinch the napes of their kittens’ necks to induce a different kind of immobility called clipnosis, which keeps their kittens quiet and easy to transport.
The physiological mechanisms behind these behaviors primarily originate in the parasympathetic nervous system, which is known for controlling resting and digesting cycles. In possums, this system causes their heart rates to drop significantly, respiration to decrease, and body temperatures to lower for up to an hour. The neurotransmitter dopamine also plays a role; for example, flour beetles with low dopamine levels tend to play dead more frequently than those with higher levels.
However, maintaining a death ruse isn’t easy. The animals must constantly assess their surroundings for cues on when it’s safe to move again. Chickens, for instance, can sense when a predator is watching them. Research shows that when a stuffed hawk was used in an experiment, the chickens came out of their catatonia more quickly when the hawk’s eyes were averted.
Some animals use TI for purposes other than defense. For example, when the sleeper cichlid feels hungry, it sinks to the lake floor and lies motionless, its coloration resembling a rotting carcass. If a small scavenger investigates, this clever fish can strike. Additionally, some animals feign death as a mating strategy. Male nursery spiders present silk-wrapped insects to attract females, who are known to eat the males. By playing dead while the female consumes her snack, these males can cautiously revive and improve their chances of mating.
While TI can be advantageous, it can also be dangerous. California orcas can flip young great white sharks, inducing TI for so long that the immobilized sharks, which need to move to breathe, essentially suffocate. Humans can also induce TI in sharks by gently stroking their snouts and turning them over, which can last up to 15 minutes—enough time for researchers to insert tags, remove hooks, or perform surgeries. However, this technique carries risks, as TI can hinder respiration and induce stress.
Humans can experience TI as well, particularly when freezing with fear during violent situations. Understanding this ancient, involuntary form of self-defense has significant implications for comprehending why some individuals don’t flee or fight in the face of danger. Studying TI in non-human animals not only sheds light on their behaviors but also helps us better understand our own responses to violence.
Playing Dead – A defense mechanism in which an animal pretends to be dead to avoid predation. – When threatened by a predator, the opossum often resorts to playing dead as a survival strategy.
Thanatosis – A biological phenomenon where an animal feigns death to evade predators. – Thanatosis is commonly observed in certain insects and reptiles as a means to increase their chances of survival.
Tonic Immobility – A temporary state of motor inhibition believed to be a defense mechanism against predators. – Sharks often exhibit tonic immobility when turned upside down, which researchers use to study them safely.
Survival – The ability of an organism to continue living and reproduce in its environment. – The survival of a species often depends on its ability to adapt to changing environmental conditions.
Predator – An organism that hunts and consumes other organisms for food. – The lion is a well-known predator that plays a crucial role in maintaining the balance of its ecosystem.
Dopamine – A neurotransmitter involved in reward, motivation, and the regulation of mood. – Increased levels of dopamine in the brain are associated with feelings of pleasure and satisfaction.
Parasympathetic – Relating to the part of the autonomic nervous system that conserves energy and slows the heart rate. – The parasympathetic nervous system helps the body relax and recover after a stressful event.
Behavior – The actions or reactions of an organism in response to external or internal stimuli. – Studying animal behavior can provide insights into their social structures and survival strategies.
Risks – The potential for loss or harm that an organism may encounter in its environment. – Animals must weigh the risks of predation against the need to forage for food.
Assessment – The evaluation or estimation of the nature, quality, or ability of something. – A thorough assessment of an animal’s habitat is essential for effective conservation efforts.
