Andean Wood Mouse Survives Extreme Cold and Low Oxygen at World's Highest Mammal Habitat

High in the Andes Mountains, a remarkable mammal defies extreme conditions: the Andean wood mouse. This tiny rodent inhabits altitudes exceeding 6,700 meters (21,981 feet), enduring sub-zero temperatures and oxygen levels less than half of those at sea level. Its ability to generate more body heat than its lowland counterparts is key to its survival.

Researchers, led by evolutionary biologist Jay Storz from the University of Nebraska-Lincoln, embarked on expeditions to the Andes, setting a new world record by capturing a specimen at 6,739 meters on the Llullaillaco volcano. Subsequent laboratory studies involved simulating the harsh environment in specialized chambers. They observed that high-altitude mice consumed oxygen at a higher rate and were more active in the cold.

Further analysis revealed that muscle shivering plays a significant role in generating extra heat for these high-altitude dwellers. Metabolic and genetic studies also showed that their blood cells possess a greater capacity to transport or buffer carbon dioxide, mitigating the risk of hyperventilation common at extreme altitudes. This physiological adaptation allows them to maintain their body temperature and thrive where mammals were previously thought unable to survive.

These findings contradict earlier beliefs that the Puna de Atacama region, with its severe hypoxia and freezing temperatures, was uninhabitable for mammals. The Andean wood mouse has evolved unique physiological traits, including enhanced thermogenic capacity, enabling it to prosper in this hostile environment. Its adaptations demonstrate a fascinating example of life's resilience and the power of evolutionary processes.