a hundred. Sleeping burrows and hibernacula are larger and more complex, with multiple entrances, deep chambers lined with plant material, and stretching to a depth of about . A colony may have up to 9 regular sleeping burrows, in addition to the larger hibernaculum. Many forms of social behaviour have been observed among hoary marmots, including play fighting, wrestling, social grooming, and nose-to-nose touching. Such activity becomes particularly frequent as hibernation approaches. Interactions with individuals from other colonies are less common, and usually hostile, with females chasing away intruders. Hoary marmots are also vocal animals, with at least seven distinct types of calls, including chirps, whistles, growls, and whining sounds. Many of these calls are used as alarms, alerting other animals to potential predators. They also communicate using scent, both by defecation, and by marking rocks or plants using scent glands on their cheeks. Hoary marmots frequently sun themselves on rocks, spending as much as 44% of their time in the morning doing so, although they will shelter in their burrows or otherwise seek shade in especially warm weather. They forage for the rest of the day, returning to their burrows to sleep during the night. In areas frequented by people, hoary marmots are not shy. Rather than running away at first sight, they will often go about their business while being watched. Mating occurs after hibernation, and two to four young are born in the spring. Males establish "harems", but may also visit females in other territories. Reproduction Hoary marmots breed shortly after, or even before, their emergence from hibernation burrows in May and in some areas (such as the eastern Cascade foothills of Washington State) as early as February. Courtship consists of sniffing the genital region, followed by mounting, although mounting has also been observed between females. Females typically raise litters only in alternate years, although both greater and lesser frequencies have been reported on occasion. Gestation lasts 25 to 30 days, so the litter of two to five young is born between late May and mid-June. The young emerge from their birth den at three to four weeks of age, by which time they have a full coat of fur and are already beginning to be weaned. The young are initially cautious, but begin to exhibit the full range of nonreproductive adult behavior within about four weeks of emerging from the burrow. Subadults initially remain with their