Adaptations of the Andean Leaf‑Eared Mouse to Extreme Altitudes

The Andean leaf‑eared mouse thrives at every altitude.

Image credit:Marcial Quiroga‑Carmona

When researchers exploring the summit of the dormant Andean volcano Llullaillaco observed a small, agile mammal darting beneath a rock, they were astonished. No mammal had previously been recorded at Llullaillaco’s 22,000‑ft elevation, yet an Andean leaf‑eared mouse (Phyllotis vaccarum) was scurrying across the volcano’s frozen surface.

In a recent study published in Science, the team detailed the biology of P. vaccarum. They uncovered genomic and metabolic adaptations that enable the mouse to endure ambient conditions where oxygen is reduced by half relative to sea level and temperatures remain below zero degrees for most of the year.

A Mammal for Every Altitude

Unlike many high‑altitude specialists, the leaf‑eared mouse also thrives at sea level. Its broad ecological tolerance has prompted investigators to compare populations across a wide elevational range.

Schuyler Liphardt, a bioinformatics data scientist at the University of Montana, and collaborators collected 167 specimens of P. vaccarum from across the species’ range. The samples included high‑elevation individuals from five expeditions in the central Andes, as well as lower‑elevation remains. The researchers also obtained related species that occupy lower altitudes for comparative purposes.

The team reared mice in laboratory conditions that simulated the low‑oxygen, low‑temperature environment characteristic of high altitudes. Highland mice produced more core body heat and exhibited greater energy production in their muscles and brown adipose tissue than both lowland relatives and the closely related Darwin’s leaf‑eared mouse (P. darwini). These findings indicate that high‑altitude mice maintain elevated body temperatures even when oxygen availability limits metabolic heat production.

Whole‑genome sequencing revealed minimal genetic divergence between high‑ and low‑land populations of P. vaccarum, suggesting that adaptive changes are traceable to specific environmental pressures rather than genetic isolation. The analysis identified several gene modifications linked to lipid metabolism and other biochemical pathways. Notably, the mice did not rely on hemoglobin alterations—a common high‑altitude adaptation in other mammals. Instead, the high‑altitude variants displayed enhanced capacity to metabolize plant toxins, potentially offering a survival advantage in a sparse high‑altitude diet.

The Metabolic Changes Sustaining P. vaccarum

These adaptations demonstrate that P. vaccarum hasMatchers fully embracedundz? Wait. Let’s rewrite: The combined findings underscore the species’ adeptness at balancing scarce resources—food, oxygen, and warmth—in an extreme environment, enabling it to survive and flourish across a remarkable elevational spectrum.

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