Habitat selection of feral yak in different time periods in Helan Mountains, China.
From July to August 2009 and from September to November 2009, we studied the habitat selections of feral yak (Bos grunnieus) during summer and autumn in Helan Mountains. From July to August, yak preferred in higher attitude (>3 000 m), in subalpine shrubland and meadow with lower tree density (<100 tree/hm2), lower tree height (<3 m), longer feral yak distance to tree (>3 m), shrub types mixture, higher shrub density (>2 000 individual/hm2), shorter distance to shrub (<1 m), higher degree position, shorter distance to water resource (<800 m or 800-1 200 m), longer distance to human disturbance (>4 000 m) and higher hiding cover (>70%). From September to November, feral yak used habitat in moderate attitude (2000-3 000 m), motane conifer forest, dominated by Ulmus glaucescens, tree density lower (<100 tree/hm2), tree height lower (<3 m), higher shrub density (<2 000 individual/hm2), feral yak distance to tree (>2 m), higher vegetation coverage (50%-70%), lower degree position, far from water resource (>1 200 m) and higher hiding cover (>70%). By principal components analysis, from July to August, the first principal component accounted for 15.679%. The higher correlation coefficients are attitude, hiding cover and tree density. From September to November, the first principal component accounted for 20.430%. The higher correlation coefficients are feral yak distance to tree, dominant tree, tree height and tree density.