JACKSON, Wyo. — Imagine sleeping for two thirds of the year.
That dream for some humans is a reality for the yellow-bellied marmots that live in the West, including in Grand Teton and Yellowstone national parks. To survive the (usually) frigid winters of western Wyoming, these marmots go into power-saving mode: according to the National Park Service, yellow-bellied marmots will hibernate from autumn through early spring. While in the hibernation state, a marmot’s body temperature can drop to approximately 41°F, and its heartbeat dips to about 30 beats per minute, down from the 180 to 200 range of its active heartbeat. The mammals also take just one to two breaths per minute.
“Marmots spend over half their lives in hibernation,” the park service states on its website. “They enter their burrows in September to early October and don’t emerge again until the following April or May. All the colony members huddle closely together in a burrow room insulated with hay. This action helps reduce some of the energy costs associated with hibernating.”
Marmots are some of the true hibernators of the Greater Yellowstone Ecosystem, a list that also includes ground squirrels and bats. Other mammals colloquially known as hibernators actually enter a state called torpor, which is similar to hibernation but not as intense or lengthy. Bears, for example, enter torpor for a few months to survive a harsh winter, but they can still occasionally wake up.
In preparation for their long winter’s nap, marmots will build up large fat stores. According to Yellowstone, their diet consists of grasses and forbs in early summer, seeds in late summer, and occasionally insects. In turn, marmots are preyed upon by coyotes, grizzlies and golden eagles.
To warn each other of predator danger, marmots will emit a loud whistle or scream, which earned them the nickname “whistle pigs.”
Marmots in Sequoia and Kings Canyon National Parks in California have been known to “dine on radiator hoses and car wiring,” per the park’s website.
“They can disable a vehicle,” that park unit’s website states. “On several occasions, marmots have not escaped the engine compartment quickly enough and unsuspecting drivers have given them rides to other parts of the parks; several have ridden as far as southern California!”
Watch for marmots this spring and summer as they emerge from their dens.
