Goals. The article aims at characterizing a unique animal of Inner and Central Asian nomads — the domestic yak (sarlyk) and its hybrid (khainak) that have been bred by Mongols and Buryats for hundreds of years. The work provides a first ethnographic insight into statistical data on yak population dynamics in synchronous and diachronous perspectives, reviews adaptive properties of the animal instrumental in surviving in extreme conditions of highlands, its exterior, breeding and behavioral specifics, economic significance. Materials and methods. The article explores literary, field and online sources to employ the methodology of comparative analysis, in particular, the comparative-historical-genetic method. Materials about yak breeding among Turkic peoples are essentially verifying by nature. Results. When it comes to declare the five traditional types of livestock bred, Mongols and Buryats mention no yak, the latter be clustered with cattle. Mongolia’s yak population ranks second worldwide — after China. The post-Socialist era witnessed an increase in yak numbers in Mongolia paralleled by a decrease in Russia. Domestic yaks have unique adaptive properties towards low oxygen partial pressure, extreme cold, and meagre fodder resources. The incomplete domestication of animals is determined by high profitability via such extensive farming techniques. Being meat, dairy and working animals, sarlyks and khainaks were most essential to the traditional economy of nomads. In the 21st century, their products become exotic and environment friendly food items, while skin, hair, wool, undercoat and other components serve as unique raw materials for light industry, pharmacology and cosmetology. Conclusions. The 21st century Mongolia with its vast yak friendly territories witnesses a significant head increase resulting in industrial processing facilities of yak raw materials nationwide. In the 1980s, the Soviets were undertaking active purposeful efforts to develop yak breeding, while the free market period decreased both numbers of animals held by Buryats and their habitat. The situation is due to the lack of demand for yak products and the lack of infrastructure for industrial processing of raw materials. The domestic yak and its hybrid had made it possible for nomads of Inner Asia — Mongols and Buryats — to significantly extend economic boundaries of their ethnic territories and inhabit montane grasslands and shrublands.