Marmots are related to ground squirrels, prairie dogs and groundhogs. The yellow-bellied marmot is a native of California and usually lives above 6000 feet elevation.
Yellow-bellied marmots are stocky herbivores with a length of 19 to 26 inches. The male weighs about 8.5 pounds while the female is smaller at 6 pounds. They have a broad head covered with dark fur and a light band of fur across the nose. As the name implies, their belly is covered in a light yellow fur which contrasts with the darker fur over the rest of the body. The tail has very dense fur and is 5 to 8 inches long. They have short stocky legs and strong claws for digging. Marmots may live up to 15 years, but spend most of that time in hibernation.
These marmots are omnivorous eating plant material, insects and bird eggs but generally eat a wide variety of plants. Their home in the meadows and slopes of northeast and southern California mountain ranges provide seeds, flowers, leaves and stems of a variety of grasses, forbs and shrubs as well as insects.
They dig burrows usually under boulders or piles of rocks to make the burrow safe from predators. They are prey to badgers, coyotes, wolves, fox, eagles, owls and wolverines.
Yellow-bellied marmots hibernate from fall to spring in burrows. Members of the colony snuggle together in their burrow lined with hay to conserve energy. During hibernation, their temperature drops to 41 degrees, their heartbeat decreases by 30 beats per minute and they take only one to two breaths per minute. Since they do not store food for hibernation, they accumulate up to 50% of their weight in fat prior to hibernation which allows them to survive so many months. They live in colonies of one or more harems each defended by a territorial male. Colonies will usually have eight to 24 marmots. Being very social animals, they play, groom and communicate with each other with whistles, screams and tooth chatters to communicate alarm or threat. Their whistles earned them the nickname “whistle pigs.”
Marmots mate within two weeks of emerging from hibernation. After a 30-day gestation period, the young are born between March and June depending on elevation. Young are born in the burrow in a nest of dry grasses. A litter will generally contain 4-6 young. Young that wean early have more time to accumulate fat for hibernation and have a greater chance of survival through the winter.
Marmots start their day with sunning on rocks and watching for predators. Mid-morning brings a peak time of foraging, then a nice rest in the burrow before foraging again mid-afternoon. While the group forages, one marmot will serve as lookout and whistle if there is danger.
The activity of marmots may benefit other animals and plants. Marmot burrows that have been abandoned become homes for other small mammals. Their habit of digging loosens and aerates the soil so plants may propagate.