Native to Eurasia and North America, there are 14 known species of marmots. Most of the rodents are quite bulky in size, their bodies usually extending from one to two feet long and weighing as much as 15 pounds. Marmots, which are mostly active at night, reach their highest weight in late summer or early fall because they build up fat reserves in preparation for winter hibernation. Their diet primarily consists of grasses and other green vegetation, a fact that results in their often being considered garden pests. The fur of marmots varies in color and length depending upon species and habitat. They may exhibit, for instance, various shades and mixtures of brown, red, black, gray, and white. Also, those that live in colder climes tend to have longer, thicker hair then those that live in warmer areas.