Animals that live at high elevations are often assumed to be at risk for extinction as habitats warm and change. But a new study led by Colorado State University researchers found that ptarmigan, which live in cold ecosystems, are not strongly affected by fluctuations in seasonal weather at two populations studied in Colorado.The results, published July 15 in the journal PLOS ONE, are surprising, given the general perception of alpine animal populations as vulnerable to recent climate warming, study authors said.Ptarmigan are grouse that live in cold ecosystems, such as alpine and tundra habitats, said Greg Wann, Ph.D. candidate in CSU's Graduate Degree Program in Ecology and a member of the Natural Resource Ecology Laboratory.The birds are well-known for changing colors seasonally. In late spring and summer, ptarmigan are brown, and in the fall, they molt into a white plumage to match the surrounding snow. The white-tailed ptarmigan is the smallest species of this type of grouse and is endemic to North America. It is the only ptarmigan that exists in Colorado.