adult males become inactive first, because they do not need to store as much fat beforehand. The parous females, yearlings, and young of the year become inactive a few weeks later, because they have to gain more weight. The marmots of a colony hibernate in a single burrow space, which they keep closed with dirt. Adults emerge in May, and the young in June. Marmots do not eat during hibernation, so they have to store fat before becoming inactive. These marmots are "deep hibernators"; they cannot easily be awoken. Their body temperature drops to below and heart rate can slow to three beats per minute. Marmots warm their bodies about every ten days. Olympic marmots lose 50% of their body mass over the seven to eight months of winter hibernation. Hibernation is the most dangerous time for them as, in years of light snowfall, as many as 50% of the young born that year will die from the cold because of the lack of insulation that is provided by good snow cover. When they emerge in early May, thick snow cover is still present from the preceding winter, so they are not very active at this time. Sometimes they are so disoriented after awaking from hibernation that they have to relearn the colony's landmarks (which are now covered in snow, which obscures them even more); they wander around aimlessly until they find their burrows. Life cycle This species, along with the hoary marmot, has the lowest reproductive rate of any rodent. A female Olympic marmot has a litter of from one to six young (3.3 on average) in alternate years. In a given year, a third of females will have a litter. Half of the pups die before the following spring. Those pups that survive the following spring can live into their teens. Both males and females mature sexually at three years, but females generally do not reproduce until they are four and a half years old. The marmot comes out from hibernation at the beginning of May, and estrus (heat) occurs about two weeks later. After hibernation ends, both male and female Olympic marmots attempt to entice the opposite sex with courtship rituals. Females who have never produced a litter before tend to be more aggressive and will chase or instigate fights with males; females which have already produced young tend to greet the male with nasal to nasal