High altitude limits the biogeography of common rats but not house mice.

Common rats (Rattus rattus and Rattus norvegicus) and the house mouse (Mus musculus) are globally distributed synanthropic rodents, yet their tolerance to high altitude has never been assessed at a global scale. We combined worldwide occurrence records with climatic and elevational data to compare their observed and potential altitudinal ranges. Using more than 200,000 curated Global Biodiversity Information Facility (GBIF) records, we assigned elevation to each occurrence and built MaxEnt species distribution models incorporating elevation and four bioclimatic variables. Rats and mice overlapped broadly at low and mid elevations; however, both rat species showed a sharp and consistent decline in occurrence above ~ 2,500 m. Only 2.3-2.7% of rat records occurred above this threshold, compared with ~ 10% for M. musculus. Species distribution models corroborated this pattern, predicting high-altitude regions, including the Andean and Tibetan plateaus, and major mountain ranges in North America and Asia, as largely unsuitable for rats but suitable for mice. Minimum and maximum temperature were the strongest predictors of habitat suitability for all species, yet elevation exerted a markedly stronger negative effect on rats than on mice. These findings identify elevation as a major global constraint on the biogeography of common rats but not house mice, likely reflecting species-specific physiological limits related to hypoxia tolerance.