By Alysia Wolf, Associate Curator of Wildlife at the High Desert Museum
On an early summer morning, before the heat of the day sets in, walking along the manicured sidewalks surrounding the Old Mill District in Bend, Oregon, you’ll most likely hear the shrill alarm whistle of a rock chuck before laying eyes on several of the chubby rodents scampering back to the safety of their underground burrows.
Rock chucks, also known as yellow-bellied marmots (Marmota flaviventris) named for the yellowish fur on their bellies, are members of the squirrel family, but don’t expect to see these stocky ground dwellers climbing any trees. Ranging in size from about 4 to 12 pounds with the males being larger than females, rock chucks stick close to their burrows, the entrance to which is hidden beneath or within a rocky outcropping for added protection from predators, which, outside the bustling Old Mill District, would include eagles, coyotes, foxes, and badgers. With healthy populations distributed throughout the western United States and Canada, rock chucks prefer moderately warm, dry habitats including grasslands, meadows, semi-deserts, and woodlands. The Old Mill District rock chucks are content to make their home amongs cyclists, joggers, and shoppers.
These marmots are diurnal and most active in the early morning and evening, resting in their burrows during the hottest time of day. Visible from April to September, omnivorous rock chucks spend much of their time eating and fattening up for winter on a diet of grasses, flowers, forbs, insects, seeds, and the occasional bird egg. One or two marmots will keep a look out for danger while the other members of the colony—up to 20 in one community—feed, groom, or rest. If danger is spotted, the high-pitched alarm call of one rock chuck will send the others back to the safety of their burrows.
Similar to their relative the groundhog, rock chucks hibernate from late September to April in underground sleeping chambers that extend below the frost line so they stay warm during the winter months. You might notice that the rock chucks are much plumper now than when they emerge from their burrows in spring, when they will once again spend their days foraging and amusing onlookers.