What do snakes do in the winter?

Written by Avalon Carthew, First Nations Conservation Technician 

This Dekay’s Brownsnake is basking on a rock.

It’s common to spot a snake basking on the sidewalk or path at a local park, enjoying the sunshine. Snakes are ectotherms, which means they rely on external sources of heat to stay warm. As such, a warm rock or sunny spot on a trail provide great spots to bask, which means to lay in the sun to increase their body temperature.  

However, with winter approaching, it’s getting colder day by day. Since snakes can’t shiver or put on sweaters like we do, their body temperature decreases with the environmental temperature, so they have to find an alternate way of surviving the winter. Snakes are currently on the move to their overwintering sites, which are called hibernacula, and reaching these areas can include traveling over a kilometer! Like many other animals, snakes are facing the big risk of habitat loss and fragmentation. While en route to their hibernacula site, snakes must contend with cars and busy roads. You may have seen snakes on roads before, but did you know that you can give them a hand?  

Your safety comes first, so before stopping to help, ensure you are able to safely stop your car and walk across the road. 99% of the time, a snakes will slither away when you step near them, but you may need to pick one up to move it off of a road. Pick up snakes gently and ensure that the length of their body is supported, and never pick up snakes by their tails or heads. Place the snake off the road in the direction it was facing. It may look like the snake is heading to some place unsuitable, but snakes know where they are going! 

What is a hibernaculum? 

This abandoned building was monitored for snakes this past spring. The wildlife fencing kept any snakes inside the perimeter of the survey area, so that Adopt-A-Pond Field Technicians could find them before they dispersed to adjacent habitats. Any snakes found were safely moved outside the fence after data was collected so that they could continue on to their summer habitat. 

Snakes overwinter in hibernacula, which are underground chambers that sit below the frost line, allowing snakes to avoid freezing. In the wild, these spaces might be found in a rock crevices or abandoned animal burrows. For example, the Narcisse snake dens in Manitoba are caverns formed by the erosion of limestone bedrock. In areas where humans live in higher densities, hibernacula could also be structures such as barns or the foundations of houses. One snake that can be found overwintering in such human-made hibernacula is the eastern milksnake, a species-at-risk in Ontario. 

This past spring, the Adopt-A-Pond Field Technicians worked with Parks Canada to identify some potential hibernacula in Rouge National Urban Park. Wildlife fencing was installed around abandoned buildings within the Park so that any snakes using the building as hibernacula would be contained within the fencing. Our team monitored these locations for snakes every morning and afternoon, measuring and identifying any snakes we found, before releasing them outside of the fencing so that they could access their summer habitat. Now that some of these buildings have been confirmed as hibernacula, Parks Canada will ensure that special care will be taken in the area for any future activities.  

Whether naturally formed or made by humans, hibernacula provide shelter from snow and cold temperatures, and are a safe place for snakes to enter brumation. To find out more about brumation, please read our previous blog posts.. During brumation, a snake’s metabolism slows down due to the decrease in body temperature. As such, its heart rate and breathing rate slow down. This means that snakes use less energy and don’t need to hunt, so they can stay in their hibernacula until the warm weather returns in the spring.  

A hibernaculum of one’s own 

This diagram shows just one potential design for a hibernaculum of your very own.

                  

Due to the habitat loss and fragmentation caused by urbanization, hibernacula can be difficult for urban snakes to find. If you share habitat with snakes and have access to a backyard or a plot of land, you can help local snakes by building your own hibernaculum! 

You will need a site with well-draining soil that is graded to ensure that stormwater runoff and snowmelt won’t flow into your new hibernaculum. Good sun exposure is also important. You will need to dig a hole that is at least 2 meters deep. This will ensure that the hibernaculum is below the frost line, but not so deep that it hits the water table. For more detailed instructions about building a hibernaculum, please visit this Toronto Zoo resource for snake hibernaculum design

You can also create a more snake-friendly property by adding basking sites like logs or flat rocks. These should be added in areas that receive full sun. Low growing native shrubs will provide additional shelter for snakes. Another option is to allow your lawn to grow longer, or even to leave a portion of your lawn unmown. Snakes can rest safely in the long grass and you can conserve gas and water at the same time! Creating habitat for snakes is a wonderful way of helping them and beautifying your backyard at the same time.  

Winter walks are always more enjoyable when you pay attention to nature, whether bird songs or animal tracks. Now that you have read our blog posts about what reptiles and amphibians do in winter, you’ll have additional topics to think about on snowy days!