Researchers discover rat mummies on the tops of ‘Martian-like’ volcanoes

The barren, windswept volcanic peaks of the Puna de Atacama region, straddling Chile and Argentina, bear a striking resemblance to the surface of Mars, which has a sparse atmosphere and frigid conditions. These peaks are located at astonishing altitudes exceeding 6,000 metres, and were previously thought to be unsuitable for the presence of mammals. However, a study was recently published in the journal Current biology Presents a groundbreaking discovery: the discovery of mummified mice in this harsh landscape, pushing the known limits of vertebrate survival on our planet.

“The most surprising thing about our discovery is that mammals can live on the tops of volcanoes in such an inhospitable environment. Mars“Well-trained mountaineers can endure such extreme altitudes during a day-long summit attempt, but the fact that rats actually live at such altitudes shows that we have underestimated “Physiological endurance of small mammals.”

This photo shows an organ of a species of leaf-eared mouse called Phyllotis vaccarum. Credit: Marcial Quiroga Carmona

Stowers and his colleagues discovered the first mouse mummy on the summit of Vulcan Saline by accident when they found the desiccated body on the edge of a rock pile. But now that they knew what to look for, they soon found others.

“Once my climbing partner and I started searching the rest of the rocks, we found seven more mummies at the same peak,” Storz recalls.

Then they began systematically searching the summits of all the Andean volcanoes. So far they have looked at 21 volcanic peaks, including 18 peaks more than 6,000 metres. Finally, they found 13 mummified mice on the summits of several volcanoes above 6,000 metres. In some cases, the mummies were accompanied by the skeletal remains of many other mice.

Video showing the site where 4 mummies were excavated from a site on the summit of Volcán Polar (6,233 m), Chile. Credit: Jay Stowers

Radiocarbon dating and genetic analysis

Radiocarbon dating has shown that mummified rats found on the tops of two volcanoes were at most a few decades old. Those at the third site were older, estimated to be 350 years old at most. Genetic analysis of the mummy’s crest showed that it represents A Classify It is called the leaf-eared mouse phyllotis vaccarumwhich is known to occur at low altitudes in the region.

“The discovery of rat mummies on the tops of these frozen, wind-swept volcanic peaks was a huge surprise,” says Stowers. “Combined with our live records of mice on the summits and sides of other high-altitude Andean volcanoes, we are collecting more and more evidence of the existence of long-term resident populations of mice living at extreme altitudes.”

This photo shows a member of the research team at the summit of Ojos del Salado, 6,893 meters (Puna de Atacama, Chile-Argentina). Credit: Mario Pérez Mamani

Explore the secrets of mammal life at high altitudes

The discovery now raises important questions, including how mammals could survive in a barren world of rocks, ice and snow where temperatures never go above freezing and roughly half the oxygen available is at sea level. It is not clear why the rats climbed to such heights. More than 500 years ago, the Incas were known to perform human and animal sacrifices on the tops of some of the Andes’ peaks. However, the researchers note that the mummified rats from the volcano peaks could not have been transported there by the Incas, since none of them were large enough to coexist with them.

In ongoing work, researchers are investigating whether high-altitude mice possess special physiological traits that enable them to survive and function in low-oxygen conditions. They are conducting physiological experiments on captive mice collected from high altitudes to find out. They are also continuing their mountaineering surveys of small mammals on the high Andean peaks of Argentina, Bolivia and Chile.

“With our mountaineering biological surveys in the Andes, we continue to make surprising new discoveries about the ecology of extreme altitude environments,” says Storz.

Reference: “Genomic insights into the mystery of rat mummies on the tops of Atacama volcanoes” by J.F. Stowers, Schuyler Lijphart, Marcial Quiroga Carmona, Naim M. Bautista, Juan C. Obazo, Timothy B. Wheeler, Guillermo D’Elia and Jeffrey M. Jude, October 23, 2023, Current biology.
doi: 10.1016/j.cub.2023.08.081

This work was funded by grants from National Institutes of HealthThe National Science Foundation, the Geographic Society, and FONDECYT.