Skull Variability and Taxonomic Issues of the Brown Bear (Ursus arctos) on the Qinghai–Tibetan Plateau

Morphometric analysis of skulls of the brown bear (Ursus arctos L.) showed the existence of two populations of this species in Tibet in the 19th century. The distribution of the northern population (I) included the Qilian Shan and Kunlun mountain ranges bordering the Tibetan plateau from the north and penetrated into the northern part of the plateau, northwestern Qinghai Province, PRC. The distribution of the southern population (II) included the upstream reaches of the main rivers of Tibet, like the Huang He, Yangtze, and Mekong on the plateau, southeastern Qinghai Province, and, most likely, all of southern Tibet, including the Himalayas of Nepal. The diagnostic features of the two populations are choanae parameters, the choanae width in males and the choanae depth in females. The noted peculiarities of Tibetan brown bears may be related to the anatomical structure of the nasopharynx, an organ of the respiratory system that allows the air to be warmed to an optimal temperature before it reaches the bronchopulmonary tissues. The divergence of Tibetan brown bear populations may be related to the settlement of the high plateau from both southern and northern refugia of the last glaciation. The currently accepted name of the subspecies of the Tibetan bear, U. a. pruinosus Blyth 1854, is suggested to be retained for the southern population (II), and that its junior synonym, U. lagomyiarius Przewalski 1883, be restored to designate the northern population (I). Clarification of the taxonomic status of the different bear populations in Qinghai Province, PRC, the most human-exploited part of Tibet, could affect the assessment of their conservation status, which is currently defined by the IUCN for all bears in Tibet as LC (Least Concern).