How the World’s Highest-Dwelling Mammal Survives Extreme Altitudes

A Record-Breaking Survival at 6,700 Meters

The Andean leaf-eared mouse (Phyllotis vaccarum) is officially the highest-dwelling mammal on Earth. Thriving at elevations exceeding 6,700 meters, these rodents persist in environments where oxygen levels sit at just 44 percent of sea-level concentration and temperatures plummet to –60º Celsius. According to research published in Science on July 9, the species survives this thin, sub-zero air by fundamentally rewiring its metabolic and cellular machinery.

Burning Fuel to Defy the Cold

Evolutionary biologist Jay Storz of the University of Nebraska–Lincoln led the team that uncovered how these mice maintain internal stability. The study reveals that highland populations exhibit a higher rate of oxygen consumption than their lowland peers, fueling a persistent level of physical activity despite the biting cold. The primary mechanism for this survival is shivering thermogenesis—the aggressive use of muscle activity to generate heat. As Storz notes, the mice are essentially directing their metabolic machinery toward the singular goal of constant body temperature regulation.

Cellular Upgrades for Low-Oxygen Life

The mouse’s resilience extends deep into its biology. The research team identified specialized mitochondria within the cells of high-altitude mice, optimized to sustain energy production even when oxygen is scarce. Beyond the mitochondria, the mice show evidence of blood cells with an enhanced capacity to store carbon dioxide. This adjustment acts as a critical safeguard, preventing the hyperventilation that typically plagues mammals in thin, high-altitude air.

Navigating a Toxic and Volcanic Range

The Andean leaf-eared mouse occupies a massive geographical footprint, stretching from the coastal deserts of Chile to the continent’s most desolate volcanic peaks. This wide range forces the species to battle two distinct threats simultaneously: extreme thermal stress and a challenging diet. Genetic analysis shows that both highland and lowland populations have evolved the ability to detoxify the specific compounds found in the plants they consume. While the link between managing a toxic diet and surviving high-altitude stress requires further study, the cumulative pressure of these environments underscores just how difficult life is for the species.

Biological Specs of the High-Altitude Specialist

• Record Holder: It is officially recognized as the highest-dwelling mammal on Earth.
• Extreme Habitat: Populations thrive at altitudes above 6,700 meters where temperatures can reach –60º Celsius.
• Metabolic Strategy: The mice utilize shivering muscles and specialized mitochondria to maintain body heat in low-oxygen conditions.
• Research Basis: Findings were detailed in a report published in the journal Science on July 9, following field expeditions led by Jay Storz and colleagues.