Alpine marmots hibernate from roughly October until April, sealing the winter chamber with soil, stones and hay. Body temperature falls to a few degrees above the burrow's, heart rate drops to a handful of beats a minute, and the animal survives entirely on fat laid down over a summer that lasts only a few months.
The social element makes the species unusual. A family group hibernates in one chamber, and periodic arousals, which are energetically expensive, tend to be coordinated across the group. Research in the Alps has shown that subordinate older offspring, particularly males, help rewarm juveniles during these arousals, and that juvenile overwinter survival is higher in groups containing such helpers. This is a form of social thermoregulation, and it is one of the reasons subordinate marmots delay dispersal.
That delay comes at a cost to the subordinates. Dominant pairs suppress reproduction in subordinates, so a helper may spend several years without breeding before inheriting or acquiring a territory of its own.