If you’ve hiked above the tree line of a mountain in Colorado, you’ve likely come across a couple fuzzy little critters making their homes among the rocks. Deer mice, in particular, are native to North America and are often found at the peaks of the Rocky Mountains. As you stand there at the summit, gasping for air after a long hike, you might have realized that the little mice don't look tired or breathless at all. They scurry around between the rocks, little balls of energy. So why is it that, at one of the highest elevations humans can reach, you’re so worn out, while the mouse is fine? In this episode, Emma speaks with Jon Velotta, assistant professor of evolutionary biology at the University of Denver, who studies how these mice have adapted to the high altitudes at which they live.  Jon Velotta is an assistant professor of evolutionary biology at the University of Denver, where he studies how animals adapt to extreme environments. Velotta’s research blends evolution with the fields of physiology and genomics. His ongoing work includes how mice have adapted to the extreme cold and low oxygen conditions of high-altitude, and how fish have made the evolutionary transition from saltwater to freshwater. More Information: Jonathan Velotta’s Google Scholar webpage “Physiological and genomic evidence that selection on the transcription factor Epas1 has altered cardiovascular function in high-altitude deer mice,” Jonathan Velotta et al “Elephants have evolved to be tuskless because of ivory poaching, a study finds,” NPR “The Genetic Basis of Chronic Mountain Sickness,” Roy Ronen, Dan Zhou, Vineet Bafna and Gabriel G. Haddad