Wake me in 9 months…

There may be times when you are so tired you feel as if you could sleep for several days - but of course that is not possible without dying from dehydration. However, some mammals have such fine control over their metabolisms, they are capable of nodding off for days or even months, in a state called hibernation. This helps an animal survive during cold periods when food is scarce. A prime example is the alpine marmot who can hibernate for up to 9 months of the year: gathering food and adding about 50% more body weight (primarily fat) as summer ends, the alpine marmot seals itself in a deep burrow, heart rate slowing to five beats per minute, breathing as little as once per minute - emerging (far lighter!) in May, when food is once again available!