page_title: Organisms at high altitude
section_title: Yaks
hierarchical_section_title: Organisms at high altitude / Mammals / Yaks
caption_attribution_description: English: Yak near Yamdrok lake, Tibet. It is a long-haired bovinae found throughout the Himalayan region of south Central Asia, the Tibetan Plateau and as far north as Mongolia and Russia. The Tibetan economy is dominated by subsistence agriculture. Due to limited arable land, the primary occupation of the Tibetan Plateau is raising livestock, such as sheep, cattle, goats, camels, yaks, dzo, and horses. The Tibetan yak is an integral part of Tibetan life. (Used in a small exhibition in Stockholm, at the World Water Week, rising awareness about climate change in the Himalayas. Original title was: "Tibet-5812") Deutsch: Yak in der Nähe des Sees Yamzhog Yumco (Yardrog Yutsho) im Kreis Nagarzê, Regierungsbezirk Shannan, Autonomes Gebiet Tibet, Volksrepublik China. Diese langhaarigen Bovinae findet man überall in der Himalaja-Region in Süd-Zentralasien, dem Hochland von Tibet und bis weit in den Norden in der Mongolei und in Russland. Die tibetanische Wirtschaft ist von landwirtschaftlicher Selbstversorgung dominiert. Wegen der begrenzten Menge landwirtschaftlich nutzbaren Bodens ist die Hauptnutzart des Tibetischen Hochlandes die Viehzucht von Schafen, Rindern, Ziegen, Kamelen, Yaks, Dzo (Kreuzung aus Yak und Rind) und Pferden. Das tibetische Yak ist ein integraler Bestandteil des tibetischen Lebens. (Verwendet in einer kleinen Ausstellung in Stockholm, Schweden während der Weltwasserwoche, die Aufmerksamkeit auf die Klimawandel im Himalaja lenkend. Der ursprüngliche Titel war "Tibet-5812")
context_page_description: Organisms can live at high altitude, either on land, in water, or while flying. Decreased oxygen availability and decreased temperature make life at such altitudes challenging, though many species have been successfully adapted via considerable physiological changes. As opposed to short-term acclimatisation, high-altitude adaptation means irreversible, evolved physiological responses to high-altitude environments, associated with heritable behavioural and genetic changes. Among animals, only few mammals and certain birds are known to have completely adapted to high-altitude environments.
  Human populations such as some Tibetans, South Americans and Ethiopians live in the otherwise uninhabitable high mountains of the Himalayas, Andes and Ethiopian Highlands respectively. The adaptation of humans to high altitude is an example of natural selection in action.
  High-altitude adaptations provide examples of convergent evolution, with adaptations occurring simultaneously on three continents. Tibetan humans and Tibetan domestic dogs share a genetic mutation in EPAS1, but it has not been seen in Andean humans.
context_section_description: Among domesticated animals, yaks (Bos grunniens) are the highest dwelling animals of the world, living at 3,000–5,000 metres (9,800–16,400 ft). The yak is the most important domesticated animal for Tibet highlanders in Qinghai Province of China, as the primary source of milk, meat and fertilizer. Unlike other yak or cattle species, which suffer from hypoxia in the Tibetan Plateau, the Tibetan domestic yaks thrive only at high altitude, and not in lowlands. Their physiology is well-adapted to high altitudes, with proportionately larger lungs and heart than other cattle, as well as greater capacity for transporting oxygen through their blood. In yaks, hypoxia-inducible factor 1 (HIF-1) has high expression in the brain, lung and kidney, showing that it plays an important role in the adaptation to low oxygen environment. On 1 July 2012 the complete genomic sequence and analyses of a female domestic yak was announced, providing important insights into understanding mammalian divergence and adaptation at high altitude. Distinct gene expansions related to sensory perception and energy metabolism were identified. In addition, researchers also found an enrichment of protein domains related to the extracellular environment and hypoxic stress that had undergone positive selection and rapid evolution. For example, they found three genes that may play important roles in regulating the bodyʼs response to hypoxia, and five genes that were related to the optimisation of the energy from the food scarcity in the extreme plateau. One gene known to be involved in regulating response to low oxygen levels, ADAM17, is also found in human Tibetan highlanders.
caption: Domestic yak at Yamdrok Lake
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