Which snake species is known to hibernate in large communal dens?

The garter snake is known to hibernate in large communal dens. More precisely, many garter snakes enter winter brumation in shared underground shelters called hibernacula. The red-sided garter snake is especially famous for gathering in enormous numbers, with tens of thousands sometimes occupying one den.

These dens protect the snakes from freezing conditions and predators during winter. Garter snakes may travel considerable distances to reach suitable sites, including abandoned mammal burrows, rock crevices, and underground cavities. Because snakes are ectothermic, their body temperature and metabolism fall with the surrounding environment.

A common mix-up is calling this process exactly the same as mammalian hibernation. Reptile specialists often use “brumation” because snakes do not regulate body heat internally like mammals do. When spring arrives, snakes emerge and may form spectacular mating balls around the den, with many males competing to mate with newly emerged females. Python, cobra, and rattlesnake are not the standard answers to this communal-den question, although some other snake species also overwinter in groups.