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Social influences on vigilance behaviour in giraffes, Giraffa camelopardalis

Citation

Cameron, EZ and Du Toit, JT, Social influences on vigilance behaviour in giraffes, Giraffa camelopardalis , Animal Behaviour, 69, (6) pp. 1337-1344. ISSN 0003-3472 (2005) [Refereed Article]


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DOI: doi:10.1016/j.anbehav.2004.08.015

Abstract

Vigilance in ungulates is considered to have a predominantly antipredator function, with the frequency and duration of scans per individual decreasing with increasing group size. Social influences on vigilance scans have been overlooked in studies on ungulates, although studies in primates and birds show that conspecific scans are important determinants of vigilance behaviour. We investigated group size effects in giraffes and examined social influences on their scanning behaviour, as well as the influence of feeding posture. We found that group size has little effect on scanning behaviour in either bulls or cows, which may be attributable to our inability to measure a group as perceived by a giraffe. Time spent scanning by lone cows did not differ from that of cows in any other group type, but time spent scanning by bulls when alone was less than that in groups. The presence of calves in a group did not influence scanning behaviour. Predation risk does not appear to be a significant modifier of vigilance behaviour, although a constant level of antipredator vigilance is probably maintained. Social factors were a significant modifier of vigilance scanning. Bulls scanned the most when they were in groups with larger bulls, and least when they were with smaller bulls. A similar pattern was seen with nearest-neighbour identity, and the identity of individuals within 10 m of a focal animal. Cows were significantly more vigilant when an adult bull was close, or was the nearest neighbour. Finally, vigilance advantages have been postulated as a determinant of sexual segregation in giraffe foraging heights but we found that the posture associated with high foraging heights imposes a vigilance cost, not an advantage. We therefore conclude that differential vigilance requirements are not a determinant of feeding height segregation between giraffe bulls and cows.

Item Details

Item Type:Refereed Article
Research Division:Biological Sciences
Research Group:Zoology
Research Field:Animal Developmental and Reproductive Biology
Objective Division:Environment
Objective Group:Control of Pests, Diseases and Exotic Species
Objective Field:Control of Pests, Diseases and Exotic Species not elsewhere classified
Author:Cameron, EZ (Professor Elissa Cameron)
ID Code:71303
Year Published:2005
Web of Science® Times Cited:56
Deposited By:Zoology
Deposited On:2011-07-13
Last Modified:2012-03-06
Downloads:10 View Download Statistics

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