Squirrels form a diverse family of rodents. Nearly 300 species have been described, and they occur in every land environment on the planet, from tropical forests to hot and cold deserts. But why are there so many species? A study led by researchers from the Complutense University of Madrid and the Institute of Geosciences (UCM-CSIC) has examined the characteristics of squirrel species that contribute to their evolutionary success in the face of global climate change.