SCOTT DETROW, HOST:
Above the clouds on the peaks of the Andes in South America live the world's highest dwelling mammal.
AILSA CHANG, HOST:
Not a mountain goat nor a llama, but the Andean leaf-eared mouse.
GUILLERMO D'ELIA: Until a few years ago, we didn't believe, we didn't know that mice can live at such high elevations.
DETROW: Guillermo D'Elia is a biologist at Austral University of Chile. He's part of a team studying life on some of the highest peaks in the Americas, places that were once thought to be too cold and too low in oxygen for mammals to survive. Their findings, published last week in the journal Science, help explain how these mice live in places once thought uninhabitable.
D'ELIA: This species, it lives from sea level up to - the highest elevation that we have recorded is 6,700 meters, right? That altitude is well over the vegetation line, you know? So there's nothing up there.
CHANG: At almost 22,000 feet, there are no trees or bushes to hide in and very little oxygen. So finding mice there raised an obvious question. How are they surviving? The only way to find out was to catch one.
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UNIDENTIFIED RESEARCHER: (Non-English language spoken).
DETROW: After chasing a mouse as it darted from stone to stone, the researchers finally had their first specimen. When they analyzed it, they discovered genetic adaptations that help the mice survive the freezing temperatures and low oxygen above the tree line.
D'ELIA: They have an adaptation at the molecular level - you know, at the genetic level, the genomic level - to generate body heat, also to deal with the low levels of oxygens.
CHANG: The team's lead researcher is Jay Storz from the University of Nebraska. He says those adaptations offer a rare chance to see how evolution solves some of nature's toughest challenges.
JAY STORZ: We identified a number of genes related to energy metabolism that appear to play a key role in enabling the high elevation mice to sustain high rates of aerobic metabolism, even in low oxygen conditions.
CHANG: Those same genetic traits could also help researchers understand conditions where the human body is deprived of oxygen, like during a stroke, for example, or when living with heart or lung diseases.
STORZ: And so there's a lot that we can learn from animals that have naturally adapted to low oxygen conditions. It can provide us with some ideas about how to treat human diseases that involve hypoxia.
DETROW: A tiny mouse living at the edge of what's survivable and helping scientists understand how life adapts when it's pushed to its limits.
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