Yellow-bellied marmots spend the summer bulking up for winter by eating grasses, flowers and other vegetation to bulk up as much as three-times their body weight to survive winter hibernation. Credit: Dawn Wilson/Dawn Wilson Photography

Move over bears. Marmots now have their own bracket-style competition to crown the largest chunkster as these captivating alpine rodents prepare for winter hibernation.

Monday, August 24, marked the launch of the inaugural Fat Marmot Week competition, an awareness event hosted by the Rocky Mountain Biological Laboratory to bring light to the challenges facing one of North America’s most charismatic alpine mammals and financially support the Marmot Project.

Started in 1962, the Marmot Project is now the world’s second-longest-running study of individually marked mammals. The information collected over those six decades has shed light not only on marmots but also on how climate change is impacting animals, plants, snowpack, and more.

“After this past winter, we had our second biggest die-off of marmots ever in the history of the Marmot Project,” said Daniel T. Blumstein, professor at UCLA and co-director of the Marmot Project at RMBL in Gothic, Colo. “We were blown away by how stark the impact of a warm, dry winter was this year.”

Three yellow-bellied marmots (Marmota flaviventris) survey their surroundings while sitting on top of a large boulder with the snow-capped mountains in the distance behind them in Rocky Mountain National Park, Colorado. Credit: Dawn Wilson/Dawn Wilson Photography

Marmots are the largest true hibernators, dropping their body temperature to just above freezing and going into a deep torpor during winter. The yellow-bellied marmots in the RMBL study hibernate for about seven months each winter. To survive the winter, the animals have to put on two to three times their body weight to have enough fat to burn during the long hibernation.

According to Emily Renkey, a master’s student at the Blumstein Lab at UCLA and a “marmoteer” working with Blumstein on the Marmot Project, the lack of snow eliminated the insulation the marmots needed to survive the cold winter temperatures.

“At the end of 2025, we had 160 marmots,” Renkey said. “It was a huge year of pups, with about 130, making it the third most pups in a year in the history of the Marmot Project.”

When the team returned in spring, however, only about 60 marmots survived the winter. The dramatic swing in climate conditions from 2025 to 2026, which caused Colorado’s warmest winter on record and a historic snow drought, impacted the survival rate of the marmots and led to the second-worst emergence rate in the history of the long-term study.

“This year we had about 77 pups born,” said Katie Adler, a Ph.D. candidate at UCLA and another “marmoteer” on the Marmot Project team. “Unfortunately, we expect about a 50% mortality rate in their first year. The biggest cause of mortality in winter is not having enough fat to burn; basically, like freezing to death.”

In the summer of 2025, the Marmot Project researchers observed about 130 pups in the study area. After a difficult winter for the marmots, the 2026 summer count of new pups fell to about 77 pups. Only about half will survive their first year. Credit: Dawn Wilson/Dawn Wilson Photography

To raise awareness about the challenges facing alpine rodents and help maintain the uninterrupted research of this long-term study, which has been hit by significant funding cuts, the team developed a fun way to talk about the challenges facing the marmots.

“Marmots are so cute, but our message has a lot of layers,” Adler said. “The competition is a fun way for people to get involved but also communicates a deeper message about science.”

The bracket of competitors in Fat Marmot Week, which includes eight marmots. The final voting takes place Aug. 28, and the chunkiest of them all will be crowned on Aug. 29.

Marmot admirers can also follow the Gothic marmots on Instagram.

Dawn Wilson is an award-winning photojournalist and travel writer who specializes in telling stories about wildlife and destinations in the Rocky Mountains. A 22-year resident of northern Colorado, including ten in Estes Park, she served as the president of the North American Nature Photography Association; is a co-host of The Nature Photographer Podcast; and guides in the Estes Park area. She is the author of “100 Things to Do in Estes Park Before You Die,” the owner of Creeks and Critters Nature Tours, a board member of the Estes Valley Watershed Coalition, a writer for Rocky Mountain Day Hikes, co-host of The Nature Photographer Podcast, a partner photographer of Girls Who Click, a member of Outdoor Writers Association of America, Her Wild Vision Initiative, Nature First, Nikon Professional Services, is Certified by Leave No Trace, and a Master Naturalist. You can follow her at https://www.dawnwilsonphotography.com/

Dawn Wilson is an award-winning photojournalist travel writer who specializes in telling the stories about wildlife and destinations of the Rocky Mountains. A 22-year resident of northern Colorado, including...