The peak of Volcán Llullaillaco lies at an elevation of 6,739 m (22,110 ft) above sea level and is located at the border between Argentina and Chile. Cold temperatures, that can drop as low as -60° Celsius, oxygen levels only 40% of what is found at sea-level, and sparse vegetation make existence on the world’s second-highest volcano too extreme for most species. The environmental limits for most mammals is believed to be 5,200 m to 5,800 m above sea level. Food availability, tolerance for hypoxia (low-oxygen conditions), and extreme cold all play a factor in limiting animals that can survive at high altitudes.
Scientists were able to document that the yellow-rumped leaf-eared mouse (Phyllotis xanthopygus rupestris) is the world’s highest-dwelling mammal. A mountaineering expedition in 2013 captured video of a mouse scampering across the snow at 6,205 m above sea level. This inspired a February 2020 expedition to the summit of Volcán Llullaillaco to look evidence of this mouse’s existence at this altitude. This expedition, led by a team of researchers from the University of Nebraska-Lincoln and Universidad Austral de Chile, were able to capture a live mouse right at the summit of Volcán Llullaillaco. The documented capture of the yellow-rumped leaf-eared mouse at the peak of Volcán Llullaillaco, makes this rodent the highest-dwelling mammal in the world.
The researchers still have more work to do to understand how this rodent is able to survive at this high of an altitude. The summit is more than a mile above the vegetation line of Llullaillaco so researchers hypothesize that lichens and insects may form the diet of this mouse. The yellow-rumped leaf-eared mouse is found at a wide range of elevations. Researchers also hope to better understand the physiological aspects of the mouse that enables it to live at such a high-altitude compared to sea-level dwellers of the same species.
Watch: The World’s Highest-Dwelling Mammal
Storz, J. F., Quiroga-Carmona, M., Opazo, J. C., Bowen, T., Farson, M., Steppan, S. J., & D’Elía, G. (2020). Discovery of the world’s highest-dwelling mammal. Proceedings of the National Academy of Sciences, 202005265. https://doi.org/10.1073/pnas.2005265117
Schrage, S. (2020, March 30). Mighty Mouse: Storz discovers world’s highest-elevation mammal. https://news.unl.edu/newsrooms/today/article/mighty-mouse-storz-discovers-world-s-highest-elevation-mammal/