The presence of mummified mice found on the summits of South American volcanoes has long suggested that rodents fed on peaks higher than 6,000 meters. It turns out that mice currently live at these extreme altitudes. These new findings call into question the previously assumed limits of animal life at such altitudes.
Mice mummified at more than 6,000 meters altitude
For many years scientists have found out mummified mice on the peaks of the Andean volcanoes. These discoveries aroused curiosity and raised questions about the reasons for their presence. According to one hypothesis, these mice were associated with ancient civilizations. especially the Incasand may have been used in sacrificial or religious rituals.
Another idea was that the presence of these rodents at such altitudes was natural. However, the researchers weren’t sure how they got there. The most widely accepted hypothesis was that these animals lived at lower altitudes and were transported to the tops of volcanoes by air currents or other means. THE local cold and dry conditions would then have supported the mummification process.
By dating the mummified mice, the researchers eventually discovered that even the oldest specimens were only a few centuries old. This revelation excludes the hypothesis of their transport by the Incas, since these mummified mice are much younger than that civilization. This therefore means that their occurrence is probably of natural origin, which calls into question the idea that they were used in sacrificial rituals.
The researchers then focused their efforts on understanding how these mice lived at such extreme altitudes, leading to surprising discoveries about the ability of these small mammals to survive in hostile conditions high in the mountains.
Rodents at over 6,700 meters
In 2013, a team of researchers isolated the presence of live mice at an extraordinary altitude of 100 m 6,205 meters on the Llullaillaco volcano, is located on the border between Argentina and Chile, in the Andean region. At the time, this was a new altitude record for the presence of vertebrates. This discovery fundamentally shook existing knowledge about the limits of animal life in high mountains.
Then, in 2020, the researchers returned to the same volcano to continue their work. This time they managed to catch even more live mice (Phyllotis vaccarum species), including one at the top of the volcano impressive height of 6,739 meters. This new discovery had confirmed that these small mammals could thrive at altitudes previously considered completely inhospitable to vertebrates.
Extreme altitudes, such as those reached by these mice, are characterized by a lack of vegetation due to harsh climatic conditions and by a much lower oxygen concentration than at sea level. The latter feature is particularly important because most mammals cannot survive in environments where oxygen is so scarce.
An Andean leaf-eared mouse, Phyllotis vaccarum, living at over 6,000 meters. Marcial Quiroga-Carmona Credits: JAY STORZ
A well-adapted species
Thus, these mice would have developed specific adaptations to overcome these unique challenges.
In recent work, a team compared the genomes of these mice that live above 6,000 meters with those of mice that live at lower altitudes. Although the genetic differences are small, they suggest that this is the case in mice from high altitudes more closely linked to each otherwhich reinforces the idea that they They breed and live at these extreme altitudes.
In addition, the researchers explain that they have identified several rodent burrows at more than 6,000 meters altitude, confirming the fact that these mice are permanent residents and not mere passageways.
However, how these mice get food and stay warm to survive in these cold environments remains a mystery. Researchers hope to solve these mysteries by studying a newly founded colony in Chile.
Details of the study are published in the journal Science.