Phyllotis vaccarum: Leaf-Eared Mouse Sets Record as World’s Highest-Dwelling Mammal
A remarkable species of leaf-eared mouse, known as Phyllotis vaccarum, has astounded scientists by making its home on the summits of the Andes mountains. These tiny mammals have set a new record as the highest-dwelling mammals in the world.
The harsh environment of the Andes mountains, with freezing temperatures reaching as low as minus 40 degrees Celsius (minus 40 degrees Fahrenheit) and vegetation hundreds of meters below, poses a significant challenge for any living creature. Yet, a team of scientists from Argentina, Chile, Bolivia, and the United States have discovered mummified mice at elevations above 6,000 meters (19,685 feet) in the Atacama Plateau of Chile and Argentina, proving that Phyllotis vaccarum has adapted to survive in such extreme conditions.
The study, recently published in Current Biology, reveals that the leaf-eared mouse species is capable of living at the highest altitudes in the world. While these mice are commonly found in the Andes mountains at lower elevations, even down to sea level, a living mouse was recorded at the summit of Llullaillaco, a volcano with an elevation of 6,739 meters (about 22,110 feet), in 2020. This extraordinary discovery prompted further expeditions by Jay Storz, a co-author of the study, who found 13 mummified mice on the Salín, Púlar, and Copiapό volcanoes.
The summits of the Andes mountains provide an inhospitable environment with freezing temperatures, winds exceeding 100 miles per hour, and oxygen levels significantly lower than at sea level. Storz, a biology professor at the University of Nebraska-Lincoln, describes these environments as “Mars-like” and emphasizes the difficulty of finding any form of life thriving in such extreme conditions. Each breath of air at these elevations contains only 40% of the oxygen available at sea level. The temperatures rarely rise above freezing, and the wind forces can reach over 116 miles per hour, making survival incredibly challenging.
However, these harsh environmental conditions create perfect conditions for preservation, effectively freeze drying the mice. In normal circumstances, mummified mice are rare due to predation. Yet, in the absence of predators at such high altitudes, the mice have been able to endure. Radiocarbon dating conducted by the research team suggests that the oldest mummies are no more than 350 years old, and some of the mice could have died recently.
The researchers are currently conducting further analysis on 31 live-trapped mice, including the record-holder mouse from Llullaillaco, to gain insights into how these mammals can survive in such extreme conditions. They are particularly interested in studying the mice’s gut contents to determine their diet. One theory is that the mice primarily consume lichens, a combination of a fungus and an alga, which are also part of the diet of some Arctic mammals. Another theory suggests that plant fragments and small insects are carried to the mountaintops by the wind.
Emmanuel Fabián Ruperto, an ecologist at the Argentine Institute for Dryland Research, stated that life at such high elevations was thought to be impossible for mammals. The survival capabilities of Phyllotis vaccarum challenge previous assumptions and surpass records set in the Himalayas and other mountain ranges. Fabián-Ruperto believes that the adaptability of these mice to higher altitudes, where they are active during the daytime, along with their exceptional evolutionary traits, allows them to thrive in seemingly uninhabitable environments.
Jay Storz concludes that this discovery demonstrates how life always manages to find a way in even the most hostile environments. By shedding light on these extraordinary adaptations, scientists hope to gain a deeper understanding of how evolution equips animals to survive in environments previously believed to be uninhabitable.