The Diet Composition Of Feral Yak In Helan Mountain, China

We collected four surveys (November2009to January2010; March to May2010; June to August2010; September to October2010) composite feces samples of feral yak in Helan Mountains to find the diet component and the proportion of it by the fecal micro-histological analysis. The results revealed that plant consumed by feral yak belonged to18families and33species. The main food of feral yak were Stipa spp., Cyperus fuscus, Agropyron cristatum, Setaria viridis, Artemisia frigida and Chloris virgata, the average relative densities (RD) in the diet composition of feral yak was54.21%. And plant of Gramineae, Compositae and Cyperaceae had high proportion of feral yak food. Feral yak foraged more Gramineae and forbs, the Rd of which was89.24%. To the contrary, shrubs and trees had low proportion.The types and proportion of plant foraged by feral yak were obviously seasonally different. Stipa spp., a part of main food in the whole year, had higher RD in spring (22.72%) and winter (35.86%) than that in summer (8.07%) and autumn (10.65%). Draba mongolica was foraged a lot in summer and autumn, but was not found in the feces analysis of spring and winer. The proportion of Gramineae, as the main food in the four seasons, had higher RD in summer (22.74%) and autumn (35.33%) than that in spring (52.76%) and winter (59.11%). The RD of Compositae in winter (23.96%) was obviously more than in the other seasons. The RD of Brassicaceae foraged by feral yak in summer and autumn were over10.00%, but under1.00%in spring and winter. Salicaceae made up the main food of feral yak in summer an autumn, but was not foraged in spring and winter. When it came to plant category, feral yak foraged a lot of Gramineae in winter, and forbs in summer and autumn. The RD of shrubs in summer (16.77%) were higher than that in the other three seasons. Trees were used by feral yak in the spring, summer and autumn almost at same, and RD in winter was lowest (0.11%).We used the results of fecal micro-histological analysis to calculate the Shannon-Wiener diversity index (H’), Pielou evenness index (J’) and niche width index (B) of feral yak. The results revealed that Shannon-Wiener diversity index and Pielou evenness index in winter were the highest in the year. And niche width index in summer and autumn were higher than the other seasons and the lowest in winter.