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Schreck rigid in a gripped swifts -Jungvogel

Paralysis is a state of complete inability to move. It occurs when an animal is threatened by a predator or is suddenly in a stressful situation for other reasons . Alternative names are rigidity, deadlocking reflex, thanatose, catalepsy and akinesia .

This behavior can be found, for example, in insects , spiders and birds , as well as in reptiles , which are threatened by snakes . In birds it is caused, among other things, by a forced supine position. Many stick insects drop with their legs stretched so that they can not be found by the predator due to their similarity to parts of plants . In laboratory rats , the rigors of fear are used to draw conclusions about the effectiveness of various drugs with regard to pain and fear reduction or the mechanisms of fear and fear processing.

Rigid horror is biologically appropriate as some predators react primarily to the movement of the prey (e.g. snakes). Rats only flee if a possibility of escape can also be recognized in a given situation; otherwise, in addition to paralysis, the body's own opioids are released - regardless of whether the triggering stimulus is a cat (as an innate enemy) or an electric shock.

The possible adaptive value of paralysis was also proven experimentally in a species of beetle ( red-brown rice flour beetle ) compared to a jumping spider species as a predator. The jumping spiders captured fewer mealworms from experimentally generated breeding lines that maintained a longer paralysis than from those that released it earlier.

In the case of the Myotonic Goats , an American goat breed , their unusual paralysis is caused by a hereditary disease ( myotonia ).

See also

Web links

Commons : Deadlock reflex  - collection of images, videos and audio files

Individual evidence

  1. ^ Erwin Hentschel, Günther Wagner: Zoological Dictionary , Gustav Fischer Verlag Jena, 4th edition 1990, ISBN 3-334-00348-5
  2. Conti et al. Footshock-induced freezing behavior in rats as a model for assessing anxiolytics
  3. ^ Anagnostaras et al .: Temporally Graded Retrograde Amnesia of Contextual Fear after Hippocampal Damage in Rats: Within-Subjects Examination.
  4. Oliver Schleif: A contribution to animal-friendly keeping of rats based on the literature (PDF; 1.3 MB)
  5. MS Fanselow, LS Lester, FJ Helmstetter: Changes in feeding and foraging patterns as an antipredator defensive strategy: a laboratory simulation using aversive stimulation in a closed economy. In: Journal of the experimental analysis of behavior. Volume 50, Number 3, November 1988, pp. 361-374, ISSN  0022-5002 . doi : 10.1901 / jeab.1988.50-361 . PMID 3209954 . PMC 1338904 (free full text).
  6. Takahisa Miyatake, Kohji Katayama, Yukari Takeda, Akiko Nakashima, Atsushi Sugita, Makoto Mizumoto (2004): Is death-feigning adaptive? Heritable variation in fitness difference of death-feigning behavior. In: Proceedings of the Royal Society London Series B. Volume 271, pp. 2293-2296. doi : 10.1098 / rspb.2004.2858