Distribution. Western North America: US Rockies, Sierra Nevada and intermountain west.
Yellow-bellied marmots are the best studied marmot species. Dr. Kenneth B. Armitage and a number of his students have studied a population in Gothic, Colorado since 1962. Yellow-bellied marmots have a "harem-polygynous" social system whereby a male defends and mates with one or more females in a subalpine meadow. Female daughters may not disperse and may settle around their mothers. Sons invariably disperse as yearlings and try to find and defend one or more females. Females tend to breed as 2-year olds. Litter sizes average a bit over four pups, of which about half survive their first year. Yellow-bellied marmots chuck, whistle, and trill when alarmed by predators; only the whistles and trills are loud alarm calls. Click on a vocalization to hear it, or read a more detailed summary of yellow-bellied marmot alarm calling.