Age-gender feeding differences in dwarf blue sheep, Pseudois schaeferi (Cetartiodactyla, Bovidae) magnified by the expansion of an invasive plant species

摘要

Understanding feeding habits and responses to habitat changes can be a critical step toward the conservation of threatened species. Pressured by hunting, habitat loss, and competition from livestock, the dwarf blue sheep (Pseudois schaeferi) of the Yangtze River gorge in the Eastern Himalaya is an IUCN-listed endangered species with a diminished range and population, and yet little is known of its basic biological requirements. Diet composition was quantified and compared between male and female adults, and juveniles of P. schaeferi on Rini Mountain, Yunnan, China from 10-min scan samples from October 2006 to February 2007. In total, 17 food species were identified though only six species (Opuntia ficus-indica, Themeda triandra, Festuca durata, P olygonum thunbergii, E lsholtzia cypriani, and Excoecaria acerifolia) made up nearly 90 % of the diet. Although feeding niches of both adults and juveniles highly overlapped, significant quantitative differences in their food composition were found. Adult male and juvenile diets were the most dissimilar; adult sheep fed more frequently on the introduced succulent cactus, O. ficus-indica, whereas juvenile sheep fed more frequently on the herbs, P. thunbergii and E. cypriani, and the woody shrub, Buddleja caryopteridifolia. Field observations showed that P. schaeferi frequently used its broad curved horns to remove the spines of O. ficusindica, presumably to gain access to the fleshy leaves. We suggest differences in the diets are the result of differential access to the cactus, but may also be influenced by nutritional requirements.