Summer diet composition of feral yak in Helan Mountains.
Fresh fecal samples of feral yak were collected during summer from June to August 2010 in the Helan Mountains. The results of microhistological analyses indicated that feral yak consumed 21 plant species (genera) which belongs to 13 families in summer. The favorite plants of feral yak in summer were Polygonum viviparum, Draba mongolica, Salix cupularis, Stipa breviflora, Cyperus fuscus, and Saussurea graminea. The main families in the summer diets of the animals were Gramineae, Chnopodiaceae, and Cyperacea. The Shannon-Wiener diversity index (H′) was -3.794, Pielou evenness index (J′) was -1.246 and niche width index (B) was 13.581 of feral yak. Feral yak's diets during summer were compared with that during spring and winner.