Life Undergound Part 2: The Secret Life of Snakes

Wednesday, November 18, 2020

From spring to late autumn, a snake's typical day looks something like this: Bask to warm up body temperature, hunt for food, hide to digest food, maybe eat again, bask some more before nightfall, and retreat to a sheltered place like under a log or rock to hide from nocturnal predators like skunks and raccoons. Snakes are ectotherms which means that they rely on their environment for heat, unlike humans who are endotherms and have specialized internal systems to regulate our body temperature. Without a source of heat to warm them up, snakes become quite sluggish and are unable to perform tasks necessary for survival like hunting for food, or fleeing from predators. Since we live in Ontario and have good ol' Canadian winters, our seventeen snake species obviously cannot just hang out in the snow all season, and require a safe place to hibernate (or brumate) until spring. That place is underground.

Eastern Gartersnake (Thamnophis sirtalis sirtalis)

While snakes don't spend much time underground during the warmer months of the year, they do seek refuge for the entirety of the winter season in what's called a hibernaculum. A snake hibernaculum (plural hibernacula) is an underground chamber where snakes can safely spend the winter protected from the frigid temperatures. Snakes aren't exactly well equipped to create their own hibernaculum, and instead search for any suitable shelter that lies below the frost line, which is three or more feet deep. Preferred sites for hibernating include but are not limited to rock piles and crevices, hollow trees, and abandoned rodent burrows. Some snakes may also choose to overwinter in basements, barns, or even junkyards - if the right shelter is there, they will seize the opportunity. Once settled in their underground living quarters, snakes will lower their metabolic rate, heart rate, and breathing rate, and go in to a deep sleep state for the winter. Unlike my subjects of the first edition of 'Life Underground' - chipmunks - who also spend winter underground, each individual snake does not usually have its own hibernaculum. Often times there will be large groups of more than one species of snake inhabiting a single underground chamber. A great example of this is the famous Narcisse Snake Dens in Manitoba, where thousands upon thousands of gartersnakes (including Red-sided Gartersnakes) gather to overwinter in massive hibernacula sites, and emerge in the spring to mate. Scroll down to the incredible video below to view the giant snake mating ball. 

Like much of our wildlife, snake populations are in decline. This is largely due to negative human impact such as road casualties, pesticide use, and habitat destruction. Snakes will generally return to the same hibernaculum year after year, sometimes travelling several kilometers to get there. When they lose that safe space or can't travel to it thanks to a new development project or other type of disturbance, they have to quickly find a new suitable area to overwinter which doesn't always work out for the best. But there are ways we can help protect snakes - I can hear some of you asking why we should protect snakes, you can find just a few reasons here - and give them safe places to hibernate, by creating man-made hibernacula structures right in our own yards. Constructing snake dens helps to replace natural ones that have been destroyed, and also may shorten a snake's travel distance in search for an overwintering shelter, which lowers their chance of being predated upon or being hit by a vehicle on a roadway. Learn more about building a snake hibernaculum here

Narcisse Snakes Dens, Manitoba


Eastern Gartersnakes emerging from hibernaculum - Photo by Kenny Ruelland

We're well into November at the moment I am writing this blog, and snakes have been sticking close to their hibernacula for several weeks now. They've been spending the warm hours of the days outside of their dens, basking and foraging nearby, retreating underground come nightfall. Now as the temperatures are falling and continue to do so, snakes will cozy up with one another and sink deep into their hibernacula, falling into that deep sleep state, not to be seen again until the snow melts and spring can be felt in the air. Being a snake sounds pretty good right now, doesn't it? 

Happy trails! 
- Shayna 

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