A team of mountaineering scientists led by Jay Storz of the University of Nebraska–Lincoln has uncovered the biological secrets of the Andean leaf-eared mouse (Phyllotis vaccarum), which lives at record-breaking altitudes on icy, dormant volcanoes in the Andes. In 2020, the team recorded these mice at 22,110 feet (6,739 meters) on the summit of Llullaillaco volcano, shattering the previous assumption that mammals could only survive up to about 18,000 feet. The conditions at these elevations are described as "godforsaken" by Storz, with thin air, freezing temperatures, and scarce water and vegetation.