Leslie, D. M., Jr., and G. B. Schaller. 2009. Bos grunniens and Bos mutus (Artiodactyla: Bovidae). Mammalian Species 836: 1–17.
Bos grunniens Linnaeus, 1766 and Bos mutus (Przewalski, 1883) are the domestic and wild forms, respectively, of the bovid commonly called the yak. B. mutus inhabits remote high-elevation alpine meadows and alpine steppe in rolling to mountainous terrain in the Tibetan Plateau, and B. grunniens is maintained widely in China, Russia, and Mongolia and uncommonly elsewhere in the world. Populations of B. mutus are substantially reduced and fragmented throughout its remaining range; the largest numbers occur in northern Tibet and western Qinghai. B. mutus is vulnerable because of poaching and competition with domestic livestock. There are as few as 10,000–15,000 B. mutus remaining in remote areas of the Tibetan Plateau; B. grunniens numbers ca. 14 million.