The yak (Bos grunniens) is a species of long-haired domesticated cattle in the family Bovidae. It is found throughout the Himalayas in Pakistan, India, the Tibetan Plateau of China, Tajikistan, and as far north as Mongolia and Siberia, Russia. Yak physiology is well adapted to high altitudes and cold weather, featuring larger lungs and heart than other cattle, a greater capacity for transporting oxygen through their blood and a thick layer of subcutaneous fat. Yaks have been domesticated in areas such as Mongolia and Tibet, primarily for their fibre, milk and meat, and as beasts of burden. Yaks' milk is often processed to a cheese called chhurpi in the Tibetan and Nepali languages, and byaslag in Mongolia, while butter made from yaks' milk is an ingredient of Tibetan butter tea. This yak was photographed near the river Chuya in the Altai Republic, a region in southern Siberia.Photograph credit: Alexandr Frolov