Stereotypy (non-human)

An elephant exhibiting stereotyped trunk swinging and rocking behaviour
For cultural depictions of animals, see Stereotypes of animals.

In animal behavior, stereotypy, stereotypical or stereotyped behavior has several meanings, leading to ambiguity in the scientific literature.[1] The terms usually refer to stereotypy, repetitive behaviors in captive animals, particularly those given inadequate mental stimulation. These behaviors may be maladaptive, involving self-injury or reduced reproductive success, and in laboratory animals can confound behavioral research.[2] References to stereotyped behavior can also refer to natural behaviors that show low variation, such as mammalian chewing cycles or fish prey-capture via suction feeding. Highly stereotyped movements may be due to mechanical constraint (such as the skull of a viper or fish, in which bones are mechanically linked), tight neural control (as in mammalian chewing), or both. The degree of stereotyping may vary between closely related species engaging in the same behavior.[1]

Examples and causes

Video of a mouse showing distinct amphetamine-induced stereotypy reminiscent of nail biting [3]

Many stereotypies can be induced by confinement; for example, cats pace in zoo cages.[4] Pregnant sows whose feed is restricted bite at their stalls' bars and chew without anything in their mouths.[5] In laboratory rats and mice, grooming is the most common activity other than sleep, and grooming stereotypies have been used to investigate several animal models of anxiety and depression.[6] Examples of stereotypical behaviors include pacing, rocking, swimming in circles, excessive sleeping, self-mutilation (including feather picking and excessive grooming), and mouthing cage bars. Stereotypies are seen in many species, including primates, birds, and carnivores. Up to 54% of elephants in zoos display stereotypical behaviors.[7][8] Stereotypic behaviour in giraffes is also common; they resort to excessive tongue use on inanimate objects, due to a subconscious response to suckle milk from their mother, which many human-reared giraffes and other captive animals do not experience.[9] Stereotypies are well known in stabled horses, usually developing as a result of being confined, particularly with insufficient exercise. They are colloquially called stable vices. They present a management issue, not only leading to facility damage from chewing, kicking, and repetitive motion, but also lead to health consequences for the animal if not addressed.[10]

Stereotypical behaviors are thought to be caused ultimately by artificial environments that do not allow animals to satisfy their normal behavioral needs. Rather than refer to the behavior as abnormal, it has been suggested that it be described as "behavior indicative of an abnormal environment."[11] Stereotypies are correlated with altered behavioral response selection in the basal ganglia.[2]

Stereotypical behavior in laboratory animals can confound behavioral research.[2] It is also seen as a sign of psychological distress in animals, and therefore is an animal welfare issue.

Solutions

Stereotypical behavior can sometimes be reduced or eliminated by environmental enrichment, including larger and more stimulating enclosures, training, and introductions of stimuli (such as objects, sounds, or scents) to the animal's environment. The enrichment must be varied to remain effective for any length of time. Housing social animals such as primates with other members of their species is also helpful. But once the behavior is established, it is sometimes impossible to eliminate due to alterations in the brain.[11]

See also

References

  1. 1 2 http://www.clemson.edu/biosci/Faculty/higham/Wainwright_etal_2008.pdf
  2. 1 2 3 Garner JP, Mason GJ. Evidence for a relationship between cage stereotypies and behavioural disinhibition in laboratory rodents. Behav Brain Res. 2002;136(1):83–92. doi:10.1016/S0166-4328(02)00111-0. PMID 12385793.
  3. ↑ Keebaugh A, Mitchell H, Gaval-Cruz M, Freeman K, Edwards G, Weinshenker D and Thomas J (2011) "PRTFDC1 Is a Genetic Modifier of HPRT-Deficiency in the Mouse" PLOS ONE, 6 (7), e22381. doi:10.1371/journal.pone.0022381
  4. ↑ Swaisgood RR, Sheperhdson DJ. Scientific approaches to enrichment and stereotypies in zoo animals: what's been done and where should we go next?. Zoo Biol. 2005;24(6):499–518. doi:10.1002/zoo.20066.
  5. ↑ Lawrence AB, Terlouw EM. A review of behavioral factors involved in the development and continued performance of stereotypic behaviors in pigs. J Anim Sci. 1993;71(10):2815–25. PMID 8226385.
  6. ↑ Kalueff AV, Wheaton M, Murphy DL. What's wrong with my mouse model? Advances and strategies in animal modeling of anxiety and depression. Behav Brain Res. 2007;179(1):1–18. doi:10.1016/j.bbr.2007.01.023. PMID 17306892.
  7. ↑ "Defra Final Report on Elephant Welfare" (PDF). Retrieved 16 November 2011.
  8. ↑ Stern A. Elephant deaths at zoos reignite animal debate. 2005-02-28 [Retrieved 2006-05-30]. Reuters.
  9. ↑ Harrison JC, George QF, Cronk CC. Stereotypic behaviour in zoo animals. J Zoo Sc. 2001;1(23):71–86.
  10. ↑ Christie, Julie Christie, (2008). "Horse Behavior and Stable Vices" (PDF). University of Minnesota Extension (Regents of the University of Minnesota).
  11. 1 2 Davis E, Down N, Garner J et al. Stereotypical behavior: a LAREF discussion [PDF]. Lab Primate Newsl. 2004 [Retrieved 2009-12-21];34(4):3–4.
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