Highest-living mammal
Phyllotis vaccarum leaf-eared mouse
6,739 metre(s)
Chile ()

A Phyllotis vaccarum leaf-eared mouse was collected at the summit of Volcán Llullaillaco, 6,739 metres (22,110 feet) above sea level in the Puna de Atacama region of northern Chile in February 2020. The field study was conducted off the back of sightings of Phyllotis mice on the same volcano at a then-record altitude of 6,205 metres (20,358 feet) in 2013. The findings were originally published in the journal PNAS on 16 July 2020 with subsequent research clarifying the species published in the Journal of Mammalogy on 5 April 2022.

The previous record holder was the large-eared pika (Ochotona macrotis), several specimens of which had been sighted at an altitude of 6,130 m (20,100 ft) during the 1921 British Mt Everest Reconnaissance Expedition, as recorded by the medical officer and naturalist A F R Wollaston.

This study paves the way for further research into other small mammals that may have been overlooked living at similar high altitudes as well as investigation into how they survive in spite of the reduced oxygen, extreme cold and limited sources of food.

Volcán Llullaillaco is the second-highest active volcano in the world after the 6,893-m (22,615-ft) Ojos del Salado. Both volcanoes sit in the Andes on the Chile-Argentina border.

The research was a collaboration between the University of Nebraska, California State University and Florida State University (all USA) and the Universidad Austral de Chile (Chile) led by Dr Jay Storz of the University of Nebraska and Professor Guillermo D'Elía of the Universidad Austral de Chile.