Marmots are growing larger and becoming hardier. These are the findings of a 33-year study by scientists at Imperial College London, the University of Sheffield and collaborators in the US that has been published in Nature magazine. Yellow-bellied marmots (Marmota flaviventris) are large ground-dwelling squirrels that live in the US' Colorado Rocky Mountains. Climate change has led to longer regional summers, with marmots hibernating for shorter periods, giving them more time to reproduce and gain weight before the next hibernation cycle. The study shows that they are growing fatter and healthier as a result.