Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Review
, 5 (3)

Giraffe Stature and Neck Elongation: Vigilance as an Evolutionary Mechanism

Affiliations
Review

Giraffe Stature and Neck Elongation: Vigilance as an Evolutionary Mechanism

Edgar M Williams. Biology (Basel).

Abstract

Giraffe (Giraffa camelopardalis), with their long neck and legs, are unique amongst mammals. How these features evolved is a matter of conjecture. The two leading ideas are the high browse and the sexual-selection hypotheses. While both explain many of the characteristics and the behaviour of giraffe, neither is fully supported by the available evidence. The extended viewing horizon afforded by increased height and a need to maintain horizon vigilance, as a mechanism favouring the evolution of increased height is reviewed. In giraffe, vigilance of predators whilst feeding and drinking are important survival factors, as is the ability to interact with immediate herd members, young and male suitors. The evidence regarding giraffe vigilance behaviour is sparse and suggests that over-vigilance has a negative cost, serving as a distraction to feeding. In woodland savannah, increased height allows giraffe to see further, allowing each giraffe to increase the distance between its neighbours while browsing. Increased height allows the giraffe to see the early approach of predators, as well as bull males. It is postulated that the wider panorama afforded by an increase in height and longer neck has improved survival via allowing giraffe to browse safely over wider areas, decreasing competition within groups and with other herbivores.

Keywords: feeding giraffe; okapi; sexual selection; silvatherium; thermoregulation.

Conflict of interest statement

The author declares no conflict of interest.

Similar articles

See all similar articles

Cited by 1 article

References

    1. Wilkinson D.M., Ruxton G.D. Understanding selection for long necks in different taxa. Biol. Rev. 2012;87:616–630. doi: 10.1111/j.1469-185X.2011.00212.x. - DOI - PubMed
    1. Taylor M.P., Weld M.J. Why sauropods had long necks; and why giraffes have short necks. PeerJ. 2013 doi: 10.7717/peerj.36. - DOI - PMC - PubMed
    1. Dagg A.I. Giraffe Biology, Behaviour and Conservation. Cambridge University Press; Cambridge, UK: 2014. p. 247.
    1. Agaba M., Ishengoma E., Miller W.C., McGarth B.C., Hudson C.N., Reina O.C.B., Ratan A., Burhans R., Chikhi R., Medvedev P., et al. Giraffe genome sequence reveals clues to its unique morphology and physiology. Nat. Commun. 2016 doi: 10.1038/ncomms11519. - DOI - PMC - PubMed
    1. Smerup M., Damkjaer M., Brøndum E., Baandrup U.T., Kristiansen S.B., Nygraad H., Funder J., Aalkjaer C., Sauer C., Buchanan R., et al. The thick left ventricular wall of the giraffe heart normalises wall tension, but limits stroke volume and cardiac output. J. Exp. Biol. 2016;219:457–463. doi: 10.1242/jeb.132753. - DOI - PubMed
Feedback