Project: Build a hibernaculum

The Pemberton Butterflyway project is an initiative from resident Dr Joti Samra to create pollinator gardens around her neighbourhood, to create a flyway for butterflies. As part of her project, she’s also sharing tips via newsletter, including this most recent encouragement, that will horrify several of my snake-averse friends, to create snake habitat on your property.

Gasp!

I know. I know. I read the story of Adam and Eve too.

But in fact, snakes are an indicator of a healthy garden. They also eat slugs and mice, and so are real adversaries in the effort to create more pollinator patches. They will bite to protect themselves, so don’t provoke the little critters – they’ll stick around if they feel safe – and we’re blessed in Pemberton with several marvellous species, none of whom are venomous. So live and let live.

And you can build a den or hibernaculum (best word ever) for your garden snakes to sit out the winter.

Have questions about the Butterflyway Project? Reach out to us at any time at butterflyway@drjotisamra.com. Or sign up for the project via this link.

Here are some awesome tips about Snake Hibernacula from the Toronto Zoo.

The Sunstone Ridge hillside is ideal snake habitat, and development there has disrupted things immensely. So, if that’s now your neighbourhood, show some love for earlier residents, and if you live elsewhere, support those who might have been displaced. (We could all be climate refugees any moment now, so build up some good karma for yourself, by being kind to those beings who are being displaced by rapid change.)

SNAKE HIBERNACULA

Snake Hibernaculum Design

Why Care About Snakes?

Snakes are often persecuted because of the mistaken belief that they are dangerous pests. However, snakes have a tremendous ecological and cultural value.

Snakes play an important role in ecosystems – they are both predator and prey.  By feeding on frogs, mice and other small animals, snakes help to maintain healthy ecosystems.  Snakes are also an important source of food and energy for birds and other larger animals. The Red-shouldered hawk, in particular, relies on snakes to feed their young.


Why Build a Hibernaculum

Habitat loss, degradation and fragmentation by roads have had an extremely detrimental affect on snake populations. A lack of adequate hibernacula (singular hibernaculum) has become a major limiting factor. Hibernacula are underground chambers that snakes use through winter to protect them from the cold.  While people have the warmth and shelter of buildings to help them survive, snakes have hibernacula.  Manmade structures such as old wells, rock and log piles, building foundations and retaining walls, and natural features such as ant mounds and groundhog or crayfish burrows are examples of snake hibernation sites.

Hibernacula are important for snakes because they require a site below the frost line and close to the water table (so the snakes do not dehydrate) to survive cold, dry winters.  Building a hibernaculum will provide more overwintering opportunities for snakes in fragmented and isolated landscapes.

Snakes are not only threatened by urban development but also by human misunderstanding.  Snake hibernacula can be constructed as an expression of acceptance and to provide valuable opportunities for education and community stewardship.  Visitors to hibernacula will be prompted to ask questions about the natural history of these fascinating creatures and the challenges they face in cold climates. 

How to Build a Hibernaculum

1. Select a well-drained site protected from cold winds, with good sun exposure (south-facing).  Ensure that surface and ground water flows away from the site (i.e. build on upland areas).  If not, drainage pipes below the frost line may be required to prevent flooding. 

2. Your snake hibernaculum can be sized to fit the available space, but it must be deeper than the frost line (at least 2 meters deep).  Snakes prefer an overwintering site that is close to the water table, but not flooded.  Moist air ensures that snakes do not dehydrate over the dry winter months. 

3. Place rubble in the bottom to create chambers for the snakes.  Chambers created at different depths allow the snakes to move vertically and horizontally to select a preferred temperature/humidity microhabitat.

4. Concrete blocks or PVC drain pipes (with holes cut into the sides along the length of the pipe) can be used for entrances and passages to allow the snakes multi-level access.  Snakes use these passage ways to move to the bottom of the pit and into the underground chambers.  It is necessary to hand place the concrete blocks to ensure that a space or tunnel extends down into the bottom of the pit at each of the corners.  Continue to fill the pit with larger rocks, old concrete blocks and slabs, maintaining as many openings and chambers as possible. 

5. Cap with an insulating layer of smaller rock rubble.  Be sure to leave the entrances open and keep the top clear of shrubs that may grow as the site matures.

6. Protect emerging snakes from predators by having cover objects such as logs, rock piles, brush and uncut grass nearby. 

7. In the spring (mid April to late May), monitor your site to determine if wildlife are using the hibernaculum. Don’t get discouraged, it may take several years before snakes discover your hibernaculum.

How to build a snake hibernaculum

Common Questions


What is a snake hibernaculum?
Hibernacula (single hibernaculum) are underground chambers that snakes use as refuges through the winter to protect them from the cold.  Snakes prefer hibernacula that are close to the water table and have a temperature that remains above freezing.  Manmade structures such as old wells, rock and log piles, retaining walls and building foundations, and natural features such as ant mounds and rodent or crayfish burrows are examples of snake hibernation sites.


Why build snake hibernacula?
Building snake hibernacula helps to create habitat and winter dens for snakes that have lost their hibernacula or cannot travel to traditional overwintering sites due to urban expansion, habitat loss and other disturbances.  Often snake hibernacula will serve as a home for other animals as well.

Will building a hibernaculum attract more snakes to my yard?
No. Building a hibernaculum will provide more habitat opportunities for the snakes that are already around your property and supported by the landscape.  It will not attract additional snakes from other areas.

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