For the U.S. Marmot, Rising Temperatures Are a Boon

As temperatures in the American West have risen in recent decades, the marmot — a mountain-dwelling rodent — has thrived, with the animals growing fatter and populations increasing as hibernation periods grow shorter, according to a new study. From 1976 to 2008, the average weight of fully grown, yellow-bellied marmots in a sample population in Colorado rose from 6.82 pounds in the early years to 7.56 pounds in the later half of the study, according to U.S. and British researchers. In addition, the population growth of the marmots increased from .56 marmots per year from 1976 to 2001 to 14.2 marmots per year from 2001 to 2008. The study, published in the journal Nature, said the marmots were growing fatter and experiencing soaring populations because rising temperatures are leading to earlier snowmelt, which causes the marmots to end their winter hibernation earlier. The animals emerge from hibernation with greater fat reserves, then spend more weeks eating in the spring, all of which has led to plumper animals that have more time to breed and are in better breeding condition. But the researchers warned that the population explosion may be short-lived, since continued warming could reduce snowpack, leading to droughts that could wither the plants on which marmots feed. The fate of the marmot contrasts with another western animal, the American pika, which has suffered as temperatures rise.