The Asiatic ibex is a threatened endemic species that is distributed in the mountains of central and northern Asia. Using the method of group scan sampling, the behaviour of the Asiatic ibex was studied in the autumn of 2005. The effects of group size and sex on vigilance were tested. The results indicated that both group size and sex affected vigilance levels. Male ibex were significantly more vigilant than females at both the group scan level (percentage of individuals scanned during a session) and group scan frequency (percentage of intervals with at least one individual scanning). The group scan level was negatively correlated with group size, and group scan frequency was positively correlated with the group size in male, female, and overall groups. These results showed that group size and sex affected vigilance in Asiatic ibex.
Vigilance is recognized as the response to potential predation threats. Many factors influence vigilance behaviour, and the effect of group size has had a great deal of attention in recent years. The group size effect hypothesis proposes that there is a negative relationship between group size and vigilance, which has been proven ture for many birds and mammal species. However this relationship has not been investigated for a number of other species including the the Equus kiang. The E. kiang is the largest wild ass in the world, and endemic to the Tibetan Plateau. Previous studies have reported its distribution and reproduction, but information about their behaviour especially their daytime activity budgets is still very limited. Also unknown is if the distinctive habitat of the Tibetan Plateau makes their behaviour different from other Equidae species. So in this paper, we discuss our behavioural observations of the daytime activity budgets and the group size effect on vigilance for the E. kiang population in the Arjinshan National Nature Reserve, Xinjiang, China. The results indicate that group size has a significant effect on the vigilance levels: with an increase in group size, both the group scan level decreased and group scan frequency increased. Our results also showed that E. kiang spent most of their time feeding (51.41
± 2.74 %), followed by moving (22.49 ± 1.40 %), standing (19.62 ± 6.74 %), resting (18.41 ± 2.13 %), and other activities (8.64 ± 0.72 %). Their feeding behaviour showed three distinct activity peaks during the day: early morning (8:00-11:00), midday (14:30-15:30), and around sunset (18:00-19:30). During the peaks of activity, E. kiang spent most of their time feeding, and during the period of inactivity, E. kiang spent most of their time resting and standing. So the group size effect was supported for E. kiang by this study, and our results are consistent with research on other Equidae species.