Group composition and seasonal changes of Bharal(
Pseudois nayaur) in Wanglang National Nature Reserve,China
ACTA THERIOLOGICA SINICA
2021, 41 (3):
Pseudois nayaur) is a common herbivore across the Tibetan Plateau, but little is known about the population at the eastern edge of its distribution. From June 2018 to August 2019, we studied the composition and seasonal changes of bharal groups in Wanglang National Nature Reserve using passive infrared camera traps. We recorded a total of 6 623 individuals belonging to 1 921 groups, with a mean group size of 3.45±2.16. The largest group comprised 23 individuals, and the smallest groups were formed by solitary individuals(both female and male). We classified six group types based on sex and age:mixed age/sex groups, ewe-lamb groups, adult male groups, adult female groups, solitary adult males, and solitary adult females. Small herd sizes(2-5 individuals) are typical of the bharal population of Wanglang National Nature Reserve, and no significant differences in group size existed among seasons. We analyzed group composition and seasonal changes of bharal and found that mixed groups were the most frequently observed, comprising 45.3% of all observations, followed by ewe-lambs, adult male groups, adult solitary males, adult solitary females, and adult female groups. The proportion of each group type varied seasonally. In spring, the highest proportion of observations were of adult male groups(29.5%) and adult solitary males(22.6%), whereas in summer, autumn, and winter mixed(58.5%, 41.8%, and 36.7%, respectively) and ewe-lamb(21.4%, 24.7%, and 18.6%, respectively) groups predominated. Observations of the individual bharal group types varied between seasons, for example, mixed groups were most frequently observed during summer, but ewe-lamb groups showed no significant change among seasons. Changes in the local environmental conditions, as well as physiological phases and their associated resource requirements are likely the mechanisms driving these temporal changes in group types and sizes.
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