Of the six marmot species in North America only two have a widespread distribution. Groundhogs (Rodentia: Sciuridae: Marmota monax) are exceedingly common in the east, but yellow-bellied marmots (Rodentia: Sciuridae: Marmota flaviventris) dominate the mountainous west. These ground squirrels inhabit slopes from the Rockies to the Sierra Nevadas and are never far from their rocky burrows.
Yellow-bellied marmots spend the short alpine summers gorging themselves mainly on grasses and other plants, and by autumn they can be rather plump. They hibernate in dens throughout the long winters and can lose about half of their body weight in that time. When they emerge in the spring eating is their top priority, but mating isn’t far behind.
Males control small territories and defend several females against other males. Pregnant females only gestate for about a month, and their litters of approximately five young are weaned within a month after that. These rodents waste little time breeding and fattening up again in the few warm months that they’re active.