English Language & Usage Stack Exchange is a question and answer site for linguists, etymologists, and serious English language enthusiasts. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm looking for a technical (medical or biological) term for when an animal freezes in response to a perceived danger. This is a pretty well known phenomenon (https://en.wikipedia.org/wiki/Fight-or-flight_response), i.e. a deer freezing in the headlights of a car, but I'm having trouble determining if there's a more precise word/phrase.

share|improve this question
up vote 17 down vote accepted

It is not actually "fight-or-flight" but rather tonic immobility. It is an instinctive reaction in many prey animals which is similar to "playing possum" or feigning death. It increases the chance that an animal's natural camouflage will work to hide it from a predator. It doesn't deter cars, though.

share|improve this answer
That's what I was looking for, thank you – spinning_plate May 14 '12 at 1:05
The word for an animal feigning death is thanatosis. – JLG May 14 '12 at 2:34
@spinning_plate Smells like a “bunny in the headlights” paralysis to me, no? – tchrist May 14 '12 at 2:50
I don't know in what context the O.P. plans to use it, but I suspect most people would be more familiar with the term "playing dead," and perhaps unfamiliar with "tonic immobility." – J.R. May 15 '12 at 8:40

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.