Sign up for CNN’s Wonder Theory science newsletter and explore the universe with fascinating news about discoveries and scientific advancements. From freezing temperatures of minus 40 degrees Celsius to vegetation hundreds of meters below the mountain tops, the summits of the Andes mountains offer an incredibly harsh environment.
How did a species of leaf-eared mouse make this barren land their home? That’s the question a team of scientists from Argentina, Chile, Bolivia, and the United States are seeking to answer. They have discovered 13 mummified mice at elevations above 6,000 meters in the Atacama Plateau of Chile and Argentina. This discovery confirms that the species, called Phyllotis vaccarum, is the highest dwelling mammal in the world, as revealed in a recent study published in Current Biology.
These mice are typically found at lower elevations in the Andes, all the way down to sea level. In 2020, a living mouse was recorded at the summit of Llullaillaco, a volcano with an elevation of about 22,110 feet. It currently holds the world record for the highest living mammal. This discovery prompted further expeditions at 21 different volcanoes, leading to the finding of the 13 mummified mice on the Salín, Púlar, and Copiapό volcanoes.
According to Jay Storz, a biology professor at the University of Nebraska-Lincoln and co-author of the study, the summits of the Andes present extremely inhospitable environments. With freezing temperatures, no vegetation, and winds that can reach over 100 miles per hour, it’s hard to overstate the challenges faced by any living creature. Each breath of air at these summits contains only about 40% of the oxygen available at sea level. These conditions have been compared to the environment on Mars, with NASA researchers even studying the area to understand how life’s building blocks might respond to similar conditions.
While the environment is not conducive to survival, it does create ideal conditions for preservation. The mice essentially become freeze-dried at these extreme heights, as they have no predators. Radiocarbon dating of the mummified mice indicates that the oldest ones are no more than 350 years old, with some possibly having died recently.
Storz highlights previous reports suggesting that these mice were used in Incan rituals. However, since the samples are not as old as the Inca civilization, the theory has been ruled out. The mystery remains as to why these mice have ascended to such extreme elevations, but Storz emphasizes that they got there on their own. The team of researchers is now studying 31 live-trapped mice, including the record-holder mouse, to understand how the species can survive in these extreme conditions. They are analyzing their gut contents to determine their diet.
One theory is that the mice eat lichens, a combination of fungus and alga that is also part of some Arctic mammal diets. This suggests that the mice may have developed an adaptability to harsh, barren environments. Another theory suggests that plant fragments, small insects, and other resources are carried to the mountaintops by the wind.
Researchers are amazed by these findings, as life at such high elevations was believed to be impossible for mammals. The leaf-eared mice weigh an average of 55 grams and their ability to maintain a steady body temperature at such altitudes is still a mystery. They are active during the daytime, unlike their nocturnal counterparts at lower altitudes.
This discovery showcases how life can find a way to thrive in seemingly uninhabitable environments. It highlights the incredible adaptability and resilience of species and how they can evolve to survive in the face of extreme conditions.
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