Sex differences in ecology of wild yaks at high elevation in the Kekexili Reserve, Tibetan Qinghai Plateau, China

Abstract

Extreme high and low altitudes and polar environments constrain the distributional limits of terrestrial mammals. In Central Asia, vegetation on the Tibetan Plateau is limited at elevations above ∼5,500 m. Although aspects of the spatial ecology of ungulates are known across many ecosystems, logistical challenges slow the development of knowledge at the upper edge of life. We studied components of the distributional ecology of wild yaks (Bos mutus) in early winter 2012. Males and females occurred above 5,000 m, but the sexes differed socially and ecologically. On average, female groups were about 15 times larger, about 100 m higher (mean elevation 4,875 m), and in wetter or more rugged topography than males. Although females with and without young did not vary in elevation, groups with calves occurred more often in habitats with steeper slopes. An ecological surrogate and congeneric, the closely related North American bison (Bos bison), also exhibits social and ecological differentiation where males occurred historically at high elevation above tree-line habitats in the Rocky Mountains. What distinguishes the present ecology and conservation of wild yaks from bison is that opportunities persist for wide-ranging yak populations across unfenced landscapes in remote protected regions of the Tibetan Qinghai Plateau.