A team of researchers from the University of Nebraska-Lincoln (UNL) confirmed and, therefore, entered the Guinness Book of Records, that a small mouse ( Phyllotis xanthopygus rupestris ) is the most resistant mammal in the world, after documenting a living specimen at an altitude of 6,739 meters.
It was precisely in February 2020, when this little yellowish-eared mouse was collected at the top of the Llullaillaco volcano, on the border between Chile and Argentina. The field study, detailed in an article published in BioRxiv in July 2020, began after sightings of mice of this species on the volcano seven years earlier.
The Lluillaillaco volcano is the second highest active volcano in the world, after Ojos del Salado, in the same mountain range and at 6,893 meters of altitude.
The record, in this case, was to find the mammal that lives at the highest altitude: 6,739 meters above sea level.
