Snake Slumber Parties

—Taro Ietaka, Director of Conservation and Land Stewardship

The most famous snake hibernaculum is Narcisse Snake Dens in Manitoba, Canada. Visitors in spring can see tens of thousands of garter snakes emerging from their dens. (Photo by J. Hazard)

All those with ophidiophobia (fear of snakes), stop reading here.

There are small caves and crevices in which garter snakes, rat snakes, and even copperheads and rattlesnakes coil together in slithery masses by the dozen, hundred, or thousand. Some of those smaller snake congregations happen right here in Westchester. These snakes are not guarding a tomb or treasure like in a scene out of Indiana Jones - they are having a giant snake slumber party.

Surviving the winter is a challenge faced by all animals in northern climes. Some animals can tough it out, putting on enough insulation to stay warm and finding enough food to survive each freezing night or snow storm. Black-capped chickadees, white-tailed deer, and other creatures you see on a winter walk have adopted that strategy. Some other animals like wood ducks and yellow warblers migrate to a location where food is more abundant. Bats and groundhogs hibernate. Snakes spend the coldest months of the year hunkered down in brumation - the cold-blooded animal's version of hibernation.

Snakes select underground dens, called hibernaculums, as their wintering places. A hibernaculum offers protection from the worst of winter, keeping its residents from freezing to death. A poorly chosen hibernaculum, one too close to the surface for example, can be disastrous and cause the loss of a snake population. Another hazard to overwintering snakes are poachers: discovered hibernaculums are sometimes raided and their individuals sold off as pets.

Snakes are not choosy bedfellows either. Species of snakes that would normally not associate or that would even eat each other, share hibernaculums. This is a safe thing to do for the possible prey because food is the last thing on a brumating snake's mind. Below a certain temperature, a cold-blooded creature can't digest food properly, so snakes stop eating a few weeks before brumation.

When winter is over, snakes emerge, warm themselves on sunny rocks, and then head off on their own to spend the rest of the year. The snake slumber party has ended.