title: Group size effects on foraging and vigilance in migratory Tibetan antelope.
abstract: Large group sizes have been hypothesized to decrease predation risk and increase food competition. We investigated group size effects on vigilance and foraging behaviour during the migratory period in female Tibetan antelope Pantholops hodgsoni, in the Kekexili Nature Reserve of Qinghai Province, China. During June to August, adult female antelope and yearling females gather in large migratory groups and cross the Qinghai-Tibet highway to calving grounds within the Nature Reserve and return to Qumalai county after calving. Large groups of antelope aggregate in the migratory corridor where they compete for limited food resources and attract the attention of mammalian and avian predators and scavengers. We restricted our sampling to groups of less than 30 antelopes and thus limit our inference accordingly. Focal-animal sampling was used to record the behaviour of the free-ranging antelope except for those with lambs. Tibetan antelope spent more time foraging in larger groups but frequency of foraging bouts was not affected by group size. Conversely, the time spent vigilant and frequency of vigilance bouts decreased with increased group size. We suggest that these results are best explained by competition for food and risk of predation.
authors.affiliation: Northwest Institute of Plateau Biology, The Chinese Academy of Sciences, Xining 810008, People's Republic of China.
authors.forename: Xinming
authors.initials: X
authors.lastname: Lian
authors.forename: Tongzuo
authors.initials: T
authors.lastname: Zhang
authors.forename: Yifan
authors.initials: Y
authors.lastname: Cao
authors.forename: Jianping
authors.initials: J
authors.lastname: Su
authors.forename: Simon
authors.initials: S
authors.lastname: Thirgood
mesh_terms: D025041:Animal Migration / Q000502:physiology; D000818:Animals; D000866:Antelopes / Q000502:physiology*; D001288:Attention / Q000502:physiology*; D005247:Feeding Behavior / Q000502:physiology*; D005260:Female; D012919:Social Behavior; D012931:Social Environment; D018609:Tibet