Hoary marmots appear to drink almost daily and they have frequently been observed eating snow. The young stay in their mother's burrow until they are approximately one month old. At this time they are fully-furred. Because they spend their first month underground, it is difficult to know how well developed the young are at birth. Once the young have emerged from the burrow, they will be weaned in about two more weeks.
Hoary marmots reach sexual maturity at two years of age.
Hoary marmots usually disperse when they are two years old. While dispersing, the mortality rate of the two year olds is very high. This may be a result of the fact that dispersing hoary marmots do not have protective burrows in which to dive into to escape predators. Hoary marmots are monestrous, that is they only have one estrous cycle per year, and thus they never produce more than one litter per year. Behavior Hoary marmot social systems are not as rigidly defined as is the case in other marmot species.