Researchers reported July 9 that Andean leaf-eared mice living around 22,000 feet survive thin, freezing air through specialized heat-producing and oxygen-processing physiology.
Experiments on 167 mice collected from 2020 to 2023 showed highland animals absorb, transport and use oxygen better than lowland mice, helping sustain shivering and body heat despite air with just 44% of sea-level oxygen.
Their advantage appears tied to more efficient, more abundant mitochondria and an unusual reliance on fats rather than carbohydrates to fuel heat production in chronic cold.
DNA comparisons also pointed to genetic changes linked to metabolism, thermoregulation and possibly detoxifying toxic high-altitude plants, one of the few food sources available in the Andes.
The work builds on the 2020 discovery of the species at 22,110-foot Llullaillaco and could eventually inform treatments for human diseases involving low oxygen delivery.