The yellow-bellied marmot is the largest member of the squirrel family. Male marmots are heavier than females, ranging from approximately 3 to 5kg, while females range in weight from 1to 4 kg. Total body length ranges from 490 to 700 mm in males and 470 to 670 mm in females. Tail length ranges from 126 to 220 mm. Yellow-bellied marmots have distinct yellow speckles on the sides of their necks, white between their eyes, yellow to red-yellow bellies and yellow-brown to tan, straight hair with white tips. Lastly, the typical life span of these marmots is 13 to 15 years (Ballenger 1996).

The yellow-bellied marmot has an annual cycle of reproduction and hibernation consisting of immergence, hibernation, emergence, reproduction, growth and preparatin for immergence. There is an age-sex sequence in emmergence and immergence patterns. Adult males emerge and immerge first, followed by adult females, yearling males, and yearling females. Reproductive maturity is not reached until the age of two due the large body size and short active season of the marmot.

The marmot is a diurnal species whose typical daily activities of the yellow-bellied marmot include foraging, sunning, grooming, and sleeping. Daily activity in this species is typically bimodal. After a period of sunning, there is a mid-morning peak of foraging activty followed by another peak in late afternoon. This pattern can fluctuate with seasonal variation (Colorado Div. of Wildlife [online] 2003).