Discovery of the world's highest-dwelling mammal

Abstract

Environmental limits of animal life are invariably revised when the animals themselves are investigated in their natural habitats. Here we report results of a scientific mountaineering expedition to survey the high-altitude rodent fauna of Volcán Llullaillaco in the Puna de Atacama of northern Chile, an effort motivated by video documentation of mice (genus Phyllotis) at a record altitude of 6,205 m. Among numerous trapping records at altitudes of >5,000 m, we captured a specimen of the yellow-rumped leaf-eared mouse (Phyllotis xanthopygus rupestris) on the very summit of Llullaillaco at 6,739 m. This summit specimen represents an altitudinal world record for mammals, far surpassing all specimen-based records from the Himalayas and other mountain ranges. This discovery suggests that we may have generally underestimated the altitudinal range limits and physiological tolerances of small mammals simply because the world's high summits remain relatively unexplored by biologists.

Keywords: Andes; Phyllotis; high altitude; hypoxia; range limits.

Fig. 1.

High-altitude survey. Map showing collecting localities in the altiplano and Puna de Atacama (A), including Volcán Llullaillaco (B), Región de Antofagasta, Chile. (C) View of Volcán Llullaillaco (6,739 m [24°43.235′S, 68°32.208′W]) from the west.

Fig. 2.

Phylogeny showing the placement of haplotypes of high-altitude Phyllotis specimens from Volcán Llullaillaco. Maximum likelihood tree obtained from analysis of 76 cytb gene sequences from specimens of 18 species of Phyllotis. Numbers denote bootstrap support values for the adjacent nodes; only values for species clades and relationships among them are shown. Inset shows details of the clades of P. x. rupestris and P. limatus. Branch tips are labeled with GenBank accession number and, when available, museum catalog number. Labels for specimens from Volcán Llullaillaco are shown in color, and the altitudes of collection localities are indicated.