Here’s How These Adorable Mice Can Live at an Extremely High Elevation Where No Other Mammal Is Known to Reside

The Andean leaf-eared mouse has adaptations that help it generate body heat efficiently in frigid, low-oxygen conditions at 22,000 feet above sea level, according to a new study

Sarah Kuta | Daily Correspondent

July 14, 2026 2:45 p.m.

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The Andean leaf-eared mouse is the highest-dwelling mammal known on the planet, capable of living roughly 22,000 feet above sea level in the Andes Mountains. But how do these tiny creatures survive in such an extreme environment, where temperatures are often well below freezing and the air contains just 44 percent of the oxygen available at sea level?

The rodents that dwell at high elevations appear to have evolved special physiological adaptations that help them generate body heat efficiently in frigid, low-oxygen conditions, scientists report in a study published July 9 in the journal Science. How and why they ventured up so high in the first place remains a mystery.

For years, researchers thought large-eared pikas, which reside up to about 20,100 feet above sea level in the Himalayas, were the world’s highest-dwelling mammals. But in 2020, a team of scientists reported that they found an Andean leaf-eared mouse living at the summit of Llullaillaco, a 22,110-foot volcano on the Argentina-Chile border, making that species the new record holder.

Andean leaf-eared mice also live at sea level and every elevation in between, so they have the broadest elevational range of any mammal.

“Evolution never ceases to surprise us,” study co-author Grant McClelland, a biologist at McMaster University in Canada, tells CBC News’ Eric Michael Johnson. “Any environment you look at on Earth, including those that seem to be completely inhospitable to life itself, you’re probably going to find something that’s found a way to survive and thrive.”

What’s more, some of the scientists who found the live mouse reported in 2023 that they identified mummified remains of the species on the summits of three different volcanoes in the Andes. That suggested that the animals routinely live at high elevations.

“From a physiological point of view, the smaller you are, the easier it is for you to lose heat,” study co-author Naim Bautista, a comparative physiologist at the University of Oklahoma, says in a statement. “Thinking about an extreme high-altitude environment where there is no oxygen, where it is freezing cold and there is virtually no food, why are these animals up there?”

For the latest study, Bautista, McClelland and their colleagues captured 167 Andean leaf-eared mice from highland and lowland elevations in the Central Andes between 2020 and 2023. They brought the creatures back to a laboratory, where they subjected them to cold, low-oxygen conditions, then compared their physiological responses.

The experiments revealed that highland mice have a greater capacity to absorb, transport and use oxygen compared to the lowland mice—a helpful adaptation for an animal that spends a lot of time shivering to stay warm but doesn’t have access to a lot of oxygen. Like a runner who’s been training for a marathon, the highlanders have built up an impressive aerobic capacity, allowing them to keep their internal furnaces burning even in thin mountain air.

Much of that improved aerobic performance seems to stem from their mitochondria, or the structures that produce the energy that powers cells. They have more mitochondria than lowland mice, per CBC News, and those abundant mitochondria are better at turning oxygen and nutrients into energy. The highlanders also seem to rely on fats—not carbohydrates—as their main energy source for generating body heat, a surprising finding that sets these mice apart from other mammals that live in chronically cold environments.

“They’re basically engaging all of their metabolic machinery toward the goal of maintaining a constant body temperature,” study co-author Jay Storz, an evolutionary biologist at the University of Nebraska–Lincoln who worked on both previous Andean leaf-eared mouse studies, tells Science News’ Erin Garcia de Jesús.

When the scientists compared the DNA of highland and lowland mice, they found specific genetic changes related to metabolism and body heat production that they think are probably related to the highlanders’ ability to survive at high elevations.

They also found genetic adaptations they suspect might play a role in neutralizing harmful chemical compounds, allowing the highlanders to eat the toxic plants that grow at high elevations in the Andes—which are often some of the only food sources available.

“Surviving in extreme elevation is much more than just about oxygen, so this [study] is refreshing,” Allie Graham, a comparative biologist at the University of Kansas who was not involved with the research, tells Science’s Yejin Lhee.

The findings deepen scientists’ understanding of a “weird animal,” Storz tells Scientific American’s Mary Randolph. But they could have even broader implications in the future. These learnings might one day help improve treatments for human conditions, such as cardiovascular diseases, in which the body’s tissues and organs don’t get enough oxygen, per a separate statement.

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Sarah Kuta is a writer and editor based in Longmont, Colorado. She covers history, science, travel, food and beverage, sustainability, economics and other topics.