Cat righting reflex

The cat righting reflex is a cat's innate ability to orient itself as it falls in order to land on its feet, often uninjured. The righting reflex begins to appear at 3-4 weeks of age, and is perfected at 7 weeksFact|date=March 2008. They are able to do this as they have an unusually flexible backbone and no functional collarbone or clavicle.

Technique

After determining up from down visually or with their vestibular apparatusFact|date=June 2008 (in the inner ear), cats manage to twist themselves to face downward without ever changing their net angular momentum. They are able to accomplish this with these key steps:
#Bend in the middle so that the front half of their body rotates about a different axis than the rear half.
#Tuck their front legs in to reduce the moment of inertia of the front half of their body and extend their rear legs to increase the moment of inertia of the rear half of their body so that they can rotate their front half quite far (as much as 90°) while the rear half rotates in the opposite direction quite a bit less (as little as 10°).
#Extend their front legs and tuck their rear legs so that they can rotate their rear half quite far while their front half rotates in the opposite direction quite a bit less.Depending on the cat's flexibility and initial angular momentum, if any, the cat may need to repeat steps two and three one or more times in order to complete a full 180° rotation. cite web
archiveurl = http://web.archive.org/web/19980528234354/http://www.usa-gymnastics.org/publications/technique/1997/2/twisting.html
archivedate = 1998-05-28
url = http://www.usa-gymnastics.org/publications/technique/1997/2/twisting.html
title = An insight into the Biomechanics of Twisting
author = Hardy Fink
accessdate = 2007-12-26] cite web
url = http://books.google.com/books?id=AfXUjLT2eK8C&printsec=frontcover&dq=zero+angular+momentum+twist
title = Superstrings and Other Things: A Guide to Physics
pages = 106,107
accessdate = 2008-06-04] [Kane, Thomas and Scher, M. P. (1969) "A dynamical explanation of the falling cat phenomenon," "International Journal of Solids and Structures", vol. 5, pages 663-670.]

Terminal velocity

In addition to the righting reflex cats have a number of other features that will reduce damage from a fall. Their small size, light bone structure, and thick fur decrease their terminal velocity. Furthermore, once righted they may also spread out their body to increase drag and slow the fall to some extent.cite web
url = http://www.ucmp.berkeley.edu/vertebrates/flight/gliding.html
title = Vertebrate Flight: Gliding and Parachuting
accessdate = 2008-06-04] A falling cat's terminal velocity is 100 km/h (60mph) whereas that of a falling man in a free-fall position is 210 km/h (130mph). At terminal velocity they also relax as they fall which protects them to some extent on impact. Padded paws will also soften impact.Fact|date=June 2008

Injury

Using their righting reflex, cats can often land uninjured. This is, however, far from always the case, and cats can still break bones or die from falls. In a 1987 study, published in the Journal of the American Veterinary Medical Association, of 132 cats that were brought into the New York Animal Medical Center after having fallen from buildings, it was found that the injuries per cat increased depending on the height fallen up to seven stories but decreased above seven stories. [cite web
url = http://www.straightdope.com/classics/a5_190.html
title = The Straight Dope: Do cats always land unharmed on their feet, no matter how far they fall?
accessdate = 2008-06-04] The study authors speculated that after falling five stories the cats reached terminal velocity and thereafter relaxed and spread their bodies to increase drag.

References

External links

* [http://www.physlink.com/Education/AskExperts/ae411.cfm How does a cat land on its legs when dropped?]
* [http://www.verrueckte-experimente.de/leseproben_e.html Falling cats]
* [http://www.cat-olholics.com/cats-land-on-their-feet.html Instinct & Normal Cat Behavior: Why Cats Land on Their Feet]
* [http://www.flycatfly.com/Parachuting_Cats.html Parachuting cats]
* [http://www.petplace.com/cats/why-cats-land-on-their-feet/page1.aspx# Why cats land on their feet]
* [http://video.nationalgeographic.com/video/player/animals/mammals-animals/cats/cats_domestic_ninelives.html?fs=animals-panther.nationalgeographic.com National Geographic video on the cat righting reflex]

Further reading

* Arabyan A, Tsai D. 1998. A distributed control model for the air-righting reflex of a cat. Biol. Cybern. 79:393-401.

ee also

* Buttered cat paradox