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词条 Cat righting reflex
释义

  1. Technique

  2. Terminal velocity

  3. Injury

  4. See also

  5. References

  6. Further reading

  7. External links

{{Merge |Falling cat problem |date=July 2018 }}

The cat righting reflex is a cat's innate ability to orient itself as it falls in order to land on its feet. The righting reflex begins to appear at 3–4 weeks of age, and is perfected at 6–7 weeks.[1] Cats are able to do this because they have an unusually flexible backbone and no functional clavicle (collarbone). The minimum height required for this to occur in most cats (safely) would be around {{convert|30|cm|in}}. Cats without a tail also have this ability, since a cat mostly moves its hind legs and relies on conservation of angular momentum to set up for landing, and the tail is in fact little used for this feat.[2]

Technique

After determining down from up visually or with their vestibular apparatus (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:

  1. Bend in the middle so that the front half of their body rotates about a different axis from the rear half.
  2. 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 further (as much as 90°) while the rear half rotates in the opposite direction less (as little as 10°).
  3. Extend their front legs and tuck their rear legs so that they can rotate their rear half further while their front half rotates in the opposite direction less.

Depending on the cat's flexibility and initial angular momentum, if any, the cat may need to perform steps two and three repeatedly in order to complete a full 180° rotation.[3][4][5]

Terminal velocity

In addition to the righting reflex, cats have other features that reduce damage from a fall. Their small size, light bone structure, and thick fur decrease their terminal velocity. While falling, a cat spreads out its body to increase drag.[6] An average-sized cat with its limbs extended achieves a terminal velocity of about {{convert|60|mph|km/h|abbr=on}}, while an average-sized man reaches a terminal velocity of about {{convert|120|mph|km/h|abbr=on}}.[7] A 2003 study of feline high-rise syndrome found that cats 'orient [their] limbs horizontally after achieving maximum velocity so that the impact is more evenly distributed throughout the body'.[8]{{rp|311}}

Injury

With their righting reflex, cats often land uninjured. However, this is not always the case, since cats can still break bones or die from extreme 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.[9] The study authors speculated that after falling five stories the cats reached terminal velocity and thereafter relaxed and spread their bodies to increase drag. However, critics of the study pointed out a survivorship bias in that instantly fatal falls were not included (as an already dead cat would not be taken to the vet), questioning the authors' conclusion that the injury rate declined for higher falls.[9] A 2003 study of 119 cats concluded that "Falls from the seventh or higher stories, are associated with more severe injuries and with a higher incidence of thoracic trauma."[10]

See also

  • Falling cat problem – the mathematical problem of explaining the physics of the cat righting reflex
  • High-rise syndrome
  • Buttered cat paradox – a humorous combination of two proverbs

References

1. ^{{cite journal |first1=Jeri A. |last1=Sechzera |first2=Susan E. |last2=Folsteina |first3=Eric H. |last3=Geigera |first4=Ronald F. |last4=Mervisa |first5=Suzanne M. |last5=Meehana |title=Development and maturation of postural reflexes in normal kittens |journal=Experimental Neurology |date=December 1984 |volume=86 |issue=3 |pages=Pages 493–505 |doi=10.1016/0014-4886(84)90084-0 |url=http://www.sciencedirect.com/science/article/pii/0014488684900840 |pmid=6499990 |accessdate=2015-01-15}}
2. ^{{cite web |url=http://helix.gatech.edu/Classes/ME3760/1998Q3/Projects/Nguyen/ |title=How does a Cat always land on its feet? |first=Huy D. |last=Nguyen |publisher=Georgia Institute of Technology, School of Medical Engineering |accessdate=2007-05-15 |deadurl=yes |archiveurl=https://web.archive.org/web/20010410235503/http://helix.gatech.edu/Classes/ME3760/1998Q3/Projects/Nguyen/ |archivedate=2001-04-10 |df= }}
3. ^{{cite journal |archiveurl=https://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 |first=Hardy |last=Fink |date=February 1997 |journal=Technique |volume=17 |number=2 |publisher=USA Gymnastics |accessdate=2007-12-26}}
4. ^{{cite book |url=https://books.google.com/books?id=AfXUjLT2eK8C |title=Superstrings and Other Things: A Guide to Physics |pages=106, 107 |first=Carlos I. |last=Calle |publisher=CRC Press |isbn=9780750307079 |accessdate=2008-06-04|date=2001-10-10 }}
5. ^{{cite journal |last=Kane |first=Thomas |last2=Scher |first2=M. P. |year=1969 |title=A dynamical explanation of the falling cat phenomenon |journal=International Journal of Solids and Structures |volume=5 |issue=7 |pages=663–670 |doi=10.1016/0020-7683(69)90086-9 |url=http://www.sciencedirect.com/science/article/pii/0014488684900840}}
6. ^{{cite web |url=http://www.ucmp.berkeley.edu/vertebrates/flight/gliding.html |title=Vertebrate Flight: Gliding and Parachuting |first=J.R. |last=Hutchinson |date=11 January 1996|publisher=University of California Museum of Paleontology |accessdate=22 December 2016}}
7. ^{{cite news |first1=D. |last1=Nasaw|title=Who, What, Why: How do cats survive falls from great heights? |date=25 March 2012 |newspaper=BBC News Online |url=https://www.bbc.com/news/magazine-17492802 |access-date=22 December 2016}}
8. ^{{cite journal |pmid=15363762 |doi=10.1016/j.jfms.2003.07.001 |volume=6 |issue=5 |title=Feline high-rise syndrome: 119 cases (1998–2001) |date=18 June 2003 |journal=J Feline Med Surg |pages=305–12 |first1=D. |last1=Vnuk |first2=B. |last2=Pirkić |first3=D. |last3=Matičić |first4=B |last4=Radisić |first5=M |last5=Stejskal |first6=T |last6=Babić |first7=M |last7=Kreszinger |first8=N |last8=Lemo |display-authors=2|url=http://jfm.sagepub.com/content/6/5/305}}
9. ^1 {{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? |website=The Straight Dope |date=1996-07-19 |first=Cecil |last=Adams |accessdate=2008-06-04}}
10. ^{{cite journal|url=http://jfm.sagepub.com/content/6/5/305|title=Feline high-rise syndrome: 119 cases (1998–2001)|first1=D.|last1=Vnuk|first2=B.|last2=Pirkić|first3=D.|last3=Matičić|first4=B.|last4=Radišić|first5=M.|last5=Stejskal|first6=T.|last6=Babić|first7=M.|last7=Kreszinger|first8=N.|last8=Lemo|date=1 October 2004|journal=Journal of Feline Medicine and Surgery|volume=6|issue=5|pages=305–312|accessdate=8 August 2016|via=jfm.sagepub.com|doi=10.1016/j.jfms.2003.07.001|pmid=15363762}}

Further reading

  • {{cite journal |last=Arabyan |first=A. |last2=Tsai |first2=D. |year=1998 |title=A distributed control model for the air-righting reflex of a cat |journal=Biol. Cybern. |volume=79 |issue=5 |pages=393–401 |doi=10.1007/s004220050488 |pmid=9851020 }}
  • {{cite journal |last=Diamond |first=J. |authorlink=Jared Diamond |year=1988 |title=Why cats have nine lives |journal=Nature |volume=332 |issue=6165 |pages=586–587 |doi=10.1038/332586a0 |pmid=3357516}}
  • {{cite journal |authorlink=Yiannis Laouris |last=Laouris |first=Y. |last2=Kalli-Laouri |first2=J. |authorlink3=Peter Schwartze |last3=Schwartze |first3=P. |year=1990 |title=The postnatal development of the air-righting reaction in albino rats. Quantitative analysis of normal development and the effect of preventing neck-torso and torso-pelvis rotations |journal=Behavioural Brain Research |volume=37 |issue=1 |pages=37–44 |doi=10.1016/0166-4328(90)90070-U |pmid=2310493}}
  • {{cite journal |last=Laouris |first=Y. |last2=Kalli-Laouri |first2=J. |last3=Schwartze |first3=P. |year=1990 |title=The influence of altered head, thorax and pelvis mass on the postnatal development of the air righting reaction in albino rats |journal=Behav. Brain Res. |volume=38 |issue=2 |pages=185–190 |doi=10.1016/0166-4328(90)90016-8 }}

External links

  • Why cats land on their feet
  • National Geographic video on the cat righting reflex
  • The miracle of the falling cat
  • How do cats always land on their feet? Super slow motion video of the African caracal.
  • [https://www.youtube.com/watch?v=RtWbpyjJqrU Slow Motion Flipping Cat Physics]
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