What the Heck is a Hibernaculum

What the Heck is a Hibernaculum?

During some fieldwork in northern Alberta, our field team came across an area that looked pretty special. It was a slumping river bank that had stabilized mid-slope on a south-west aspect. The slump had occurred long ago, and had stabilized so that mature white spruce trees had grown up in the hollow between its base and its toe. Veteran field biologist, Joseph Litke, was on the field team on that day, and he flagged the site as a likely candidate for supporting a garter snake hibernaculum even though, over the course of several days of intense summer fieldwork, not a single garter snake had been observed. Read on to answer that burning question “What the Heck is a Hibernaculum, anyway?” 

In early October, a time of the year when garter snakes begin to congregate near their winter den sites, Joseph returned to the site he had identified to see if maybe he was right. In fact, he did see garter snakes congregating near the site he had singled out. He counted numerous individual snakes all within 5 meters of one another at that location. He was also able to observe them emerging from, and retreating to an underground system of small tunnels at the same location. He reported his findings to the regional Provincial Biologist for the area, to be added to their database of important wildlife sightings.

For those of us who are not snake experts, and are still wondering “What the heck is a hibernaculum?”, hibernacula (plural) are the winter dens of snakes, an area (usually underground) where snakes can overwinter without freezing. Snakes seek out all sorts of areas to use as hibernacula, such as old wells, retaining walls, old animal burrows, river valley slumps, etc. (Alberta Conservation Association). These sites are often south-facing to increase the warmth of the den. Different types of snakes can be found to hibernate together in hibernacula, and will return to the same one year after year. 

A red-sided garter snake emerges from its underground hibernaculum to soak up the sun of a warm autumn afternoon in northern Alberta

Alberta is home to seven types of snakes of which three types are garter snakes; the Plains Garter snake, the Wandering Gartner Snake and the Red-sided Garter snake. The garter snakes Joseph observed were Red-sided Garter Snakes, the most wide-ranging snake in Alberta that can be found in the boreal forest, foothills and parkland regions (Alberta Conservation Association). The other two types of Alberta garter snakes have smaller ranges, with the Wandering Garter Snake occupying an area along the foothills and the Peace River Valley, south of the Red Deer River, and the Plains Garter Snake in the southern and eastern parts of Alberta (Alberta Conservation Association). 

Red-sided Garter Snake (Thamnophis sirtalis). Photo: Kris Kendell, with permission
Plains Garter Snake (Thamnophis radix). Photo: Kris Kendell, with permission.
Wandering Garter Snake (Thamnophis elegans). Photo: Kris Kendell, with permission.

While snakes are often feared, and therefore vilified, they are an essential part of natural ecosystems, as they are a significant factor in controlling rodent and insect species, and they are also an important food source for mammals and raptors (Government of Alberta). All snakes in Alberta are protected under the Alberta Wildlife Act which means it is illegal to kill, posess, buy or sell snakes native to Alberta. Their hibernacula are also protected by the same Act. Unfortunately, this doesn’t mean that snakes in Alberta have had it easy, as their habitat is often destroyed by humans. Urban and agricultural land use is often in conflict with snake habitat and this threatens their persistence in Alberta. All garter snake species in Alberta fall under the status of Sensitive, a designation which means that while it is currently not at risk of extinction, it requires special protection to ensure it doesn’t become at risk.

A garter snake emerges from its underground hibernaculum to soak up the sun of a warm autumn afternoon in northern Alberta

Conservation organizations are still trying to better understand reptiles in Alberta, so if you’re like Joseph and you find a unusual abundance of snakes associated with a particular location, you can submit your observations to the Alberta Volunteer Amphibian Monitoring Program.

If you have a less savoury encounter with a snake (such as finding one snuggled up in your basement), it is always best to leave it be and call your local Fish and Wildlife officer. 

If you have been told that your proposed development has the potential to impact snakes, and you need an expert to assess the risk, consider contacting a wildlife professional who can help

A baby red-sided garter snake being admired by a curious hiker, Beaver Hills, Alberta