How snakes overwinter

A hibernaculum is a place where a snake overwinters. This is usually a natural feature of a landscape such as another animal’s burrow, rock pile, or dead tree. It can also be man-made like a building foundation, or an old well. The hibernacula must meet specific characteristics to keep a snake safe over the cold winter months. When a snake is brumating below ground the space must maintain a consistent temperature above 0°C so it does not freeze. The den should be below the frost line, which could mean descending over 1 meter below ground. A well-insulated hibernaculum makes it easier for the snakes to maintain a low metabolic rate.

While the den keeps the snake at the righ temperature, the metabolic rate is consistently lower, and they use less energy and can last longer in brumation. They do not need to eat while in brumation but they still need to consume water so there must be an accessible source. As water below the frost line remains liquid throughout the winter and typically maintains a steady temperature of 4-6°C, hibernacula in areas with a high water table can be less prone to sudden changes in temperatures. This consistent temperature can not only protect snakes from sudden cold or warm temperatures which could harm them, it also allows snakes to maintain a consistently lower metabolic rate. However, should a snake get trapped in a flooded hibernaculum, it could eventually drown without access to air.

Snakes in Canada generally brumate from late October to March or April. Some species of snakes prefer to brumate alone or in small numbers while other species do so in groups, possibly due to a limited availability of hibernation sites. It can also be beneficial to brumate in groups as it means that potential mates will be close by after emergence.