Black-and-white snub-nosed monkeys (
Rhinopithecus bieti
) distribute in a restricted area of the TransHimalayas between the Mekong and Yangtze River, at 26°14’N-29°20’N and 99°15’E−99°37’E. There are about 1 700 individuals in 15 groups remained in the habitat between 4 200 (north) −2 600 m (south) asl. The Milaka group is the northernmost range of the species with about 50 individuals in Mangkang county of Tibet. Based on our field survey and previous reports, we identified the fir forest and the mixed conifer forest as suitable habitat for the monkeys. Summer grazing lands and farmlands, which were made by local people’s cutting and burning in the fir forest at the high and low altitude belt, are replacing fir forest. To evaluate the status of the monkeys’ habitat, we employed GIS and RS to identify the habitat types with Landsat TM satellite imagery in winter of 1986 and 2006 respectively. The work resulted in: 1) the size of summer grazing lands, farmlands, and fir forest was 4 900 hm
2, 3 300 hm
2 and 13 600 hm
2 in 2006 respectively; 2) during the past 20 years (1986−2006), the size of fir forest decreased by 15.5% (2 500 hm
2), summer grazing lands and farmlands increased by 58.1% (1 800 hm
2) and 17.8% (500 hm
2) respectively; 3) the habitat of the species was more fragmented, the number of habitat patches increased by 75.6%, the mean size of forest patches decreased by 51.8% (from 15.3 to 7.4 hm
2), the largest patch index decreased by 54.7%; the patch richness remained the same, but the Shannon’s diversity index and the Shannon’s evenness index increased by 4.0%, respectively; and 4) the size of fir forest negatively correlated with villager population (r =−1.000), but the size of summer grazing lands and farmlands positively correlated with villager population (r = 1.000). These indicate the habitat lost and fragmentation for the Milaka group increased sharply during the past 20 years and it is the result of population growth and the most employment of traditional modes.
