This Critter’s House Is a 22,000-Foot Volcano With Scarce Food, Little Oxygen and Near-Freezing Temps

At 22,000 feet (6,706 meters) above sea level, the air offers less than half the oxygen available at sea level and temperatures are almost always below freezing. The Andean leaf-eared mouse lives there anyway.

It is the highest-dwelling mammal known on Earth, found on Andean volcano summits once considered too hostile for vertebrates. The same species also lives all the way down at sea level, giving it the broadest elevation range of any mammal.

Researchers studying mice from different elevations found that the highlanders have remodeled their bodies around one brutal problem: staying warm when oxygen is scarce. They are better at absorbing, transporting and using oxygen, and their cells convert that oxygen into energy more efficiently. They also lean on fat rather than carbohydrates to fuel that heat production.

That matters because a tiny mammal in extreme cold has to keep generating heat just to maintain its body temperature. Doing that normally requires plenty of oxygen. These mice have found ways to keep the furnace running with much less.

Then researchers found another adaptation they were not looking for. The mice show genetic changes associated with breaking down plant toxins, potentially allowing them to eat some of the few plants available at high elevations. Scientists do not yet know exactly which plants or toxins are involved.

How and why the mice first climbed that high remains a mystery science hasn't solved.

The highest-living mammal on Earth has given up several of its survival tricks. How it got up there in the first place, it still isn't telling.

Read the full story at Smithsonian Magazine, July 14, 2026

Hot Take: Most mammals would take one look at that mountain and renegotiate the lease. This mouse apparently treated 22,000 feet as a fixer-upper.