A Virginia opossum displaying tonic immobility Once it enters this state, an opossum may remain motionless for up to four hours. During this time its heart rate decreases by 46 percent, its breathing slows by 31 percent, and its body temperature drops by 0.6 ℃ (33 ℉). (more) tonic immobility nature’s ultimate survival act Ask the Chatbot a Question More Actions Share Share Share to social media Facebook X URL https://www.britannica.com/science/tonic-immobility Feedback Corrections? Updates? Omissions? Let us know if you have suggestions to improve this article (requires login). Feedback Type Select a type (Required) Factual Correction Spelling/Grammar Correction Link Correction Additional Information Other Your Feedback Submit Feedback Thank you for your feedback Our editors will review what you’ve submitted and determine whether to revise the article.

　　External Websites Ask the Chatbot a Question Also known as: death feigning, playing dead, playing possum, thanatosis Written by Manjishtha Bhattacharyya Manjishtha Bhattacharyya is an editor at Encyclopaedia Britannica. She holds a PhD in zoology from Vidyasagar University, West Bengal, and has more than seven years of experience in science communication... Manjishtha Bhattacharyya Fact-checked by The Editors of Encyclopaedia Britannica Encyclopaedia Britannica's editors oversee subject areas in which they have extensive knowledge, whether from years of experience gained by working on that content or via study for an advanced degree.... The Editors of Encyclopaedia Britannica Last Updated: Aug 21, 2025 • Article History Table of Contents Table of Contents Ask the Chatbot Also called: thanatosis, playing dead, and death feigning (Show more) { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type" : "Question", "name" : " What is tonic immobility? ", "acceptedAnswer" : { "@type" : "Answer", "text" : "Tonic immobility is an unlearned, reflexive, and reversible behavioral state in animals characterized by extreme motor inhibition, making them appear lifeless. It is observed mainly in predator-prey interactions." } } , { "@type" : "Question", "name" : " How does tonic immobility manifest in different species? ", "acceptedAnswer" : { "@type" : "Answer", "text" : "In insects, abdominal pumping decreases and heart rate appears to increase. In vertebrates, heart and breathing rates lower, and the animal may salivate, defecate, urinate, and bleed. Some animals produce foul-smelling secretions and stick out their tongues." } } , { "@type" : "Question", "name" : " What are the functions of tonic immobility? ", "acceptedAnswer" : { "@type" : "Answer", "text" : "Tonic immobility helps animals escape predation, ensure or avoid mating, attract prey, and avoid aggression. It offers advantages such as repelling predators through foul-smelling secretions or making prey less attractive by appearing dead." } } , { "@type" : "Question", "name" : " How is tonic immobility controlled in animals? ", "acceptedAnswer" : { "@type" : "Answer", "text" : "Tonic immobility involves multiple structures and chemical messengers in the nervous system, such as excitatory and inhibitory motor neurons, dopamine, and serotonin. It is influenced by such factors as age, body size, mating status, and environmental conditions." } } ] } Top Questions What is tonic immobility? Tonic immobility is an unlearned, reflexive, and reversible behavioral state in animals characterized by extreme motor inhibition, making them appear lifeless. It is observed mainly in predator-prey interactions.

　　How does tonic immobility manifest in different species? In insects, abdominal pumping decreases and heart rate appears to increase. In vertebrates, heart and breathing rates lower, and the animal may salivate, defecate, urinate, and bleed. Some animals produce foul-smelling secretions and stick out their tongues.

　　What are the functions of tonic immobility? Tonic immobility helps animals escape predation, ensure or avoid mating, attract prey, and avoid aggression. It offers advantages such as repelling predators through foul-smelling secretions or making prey less attractive by appearing dead.

　　How is tonic immobility controlled in animals? Tonic immobility involves multiple structures and chemical messengers in the nervous system, such as excitatory and inhibitory motor neurons, dopamine, and serotonin. It is influenced by such factors as age, body size, mating status, and environmental conditions.

　　tonic immobility, unlearned, reflexive, and reversible behavioral state in animals characterized by extreme motor inhibition (an almost complete suspension of immediate and automatic actions in response to a stimulus), which may make an animal appear lifeless. Animals may enter this state under different situations, but it is most frequently seen in the context of predator-prey interactions. An animal displaying tonic immobility has an altered heart rate and stiff legs—making it look dead—and may remain motionless for hours. In this state the animal remains largely unresponsive to external stimuli. Tonic immobility has been observed in a wide range of species—from insects ...(100 of 1248 words)

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