Yaks are biologically unable to survive at low altitudes.

The domestic yak (Bos grunniens) has evolved over thousands of years to thrive in the Tibetan Plateau at altitudes between 3,000 and 5,000 meters. Their physiology is uniquely adapted to low-oxygen environments. They have larger hearts and lungs than cattle, and their blood has a higher concentration of red blood cells to transport oxygen efficiently.However, these same adaptations become a liability at sea level. Yaks possess a thick layer of subcutaneous fat and a dense, double-layered coat of long hair and matted wool. Unlike most mammals, they have very few functional sweat glands, which means they cannot dissipate heat through evaporation. When exposed to temperatures above 15°C (59°F), their metabolic rate increases as they struggle to stay cool.Research published in journals like 'Nature Genetics' highlights that yaks have specific gene mutations, such as in the ADAM17 gene, which help them cope with low oxygen but offer no protection against heat. In lowlands, the denser air and higher temperatures lead to 'lowland disease.' This condition causes pulmonary hypertension and right-sided heart failure as the animal's cardiovascular system overworks.Because of these biological constraints, yaks kept in zoos in warmer climates require specialized air-conditioned enclosures. Without these interventions, the chronic heat stress leads to lethargy, suppressed immune systems, and eventually death. Their evolutionary specialization makes them one of the few species on Earth physically tethered to high-altitude ecosystems.