Yellow-bellied Marmot

A yellow-bellied marmot in a snow-covered woody area
After hiberating for up to eight months, yellow-bellied marmots emerge between February and May.

NPS/Neal Herbert

Black track of a yellow-bellied marmot
Yellow-bellied marmot track

Scientific Name

Marmota flaviventris


  • 20–28 inches long; 3.5–11 pounds.
  • One of the largest rodents in Yellowstone.
  • Reddish-brown upper body; yellowish belly; small ears; prominent active tail.


  • Found from lowest valleys to alpine tundra, usually in open grassy communities and almost always near rocks.
  • Feed on grasses and forbs in early summer; switch to seeds in late summer, occasionally will eat insects.
  • Prey for coyotes, grizzlies, and golden eagles.


  • Hibernate up to 8 months, emerging from February to May depending on elevation; may estivate in June in response to dry conditions and lack of green vegetation and reappear in late summer.
  • Breed within two weeks of emerging from hibernation; average five young per year.
  • Active in morning, late afternoon, and evening.
  • Colonies consist of one male, several females, plus young of the year.
  • Vocalizations include a loud whistle (early settlers called them “whistle pigs”), a “scream” used for fear and excitement; a quiet tooth chatter that may be a threat.
  • Males are territorial; dominance and aggressiveness demonstrated by waving tail slowly back and forth.
A wolf standing on a snowy bank near brown grass howls


Home to the largest concentration of mammals in the lower 48 states.

Last updated: October 22, 2020

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Yellowstone National Park, WY 82190-0168



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