When it is not covered with snow, the Sancy massif seems like a museum of natural history. It is indeed home to the two nature reserves of Chastrey-Sancy and Chaudefour Valley, carved out by glacial erosion. The first is home to more than a thousand different plant species, including six endemic to Auvergne. It also houses an essentially mountainous fauna of mouflons, chamois, deers, and marmots and more than 130 bird species. The Chaudefour Valley nature reserve serves as a habitat for more than 970 animal species.