Building a home for an endangered snake
Posted onJuly 27, 2023by, , ,
Candace Park holding a blue racer. Photo: Hannah McCurdy-Adams
This is the second installment of our series on the many facets of the blue racer conservation project on Pelee Island.
What is being done to create critical blue racer habitat.
Previously, we discussed the types of habitats that blue racers rely on (i.e., alvars, grasslands, and open woodlands). However, blue racers also require specific features within these habitats in order to carry out essential parts of their life cycle, like nesting and hibernation.
Blue racer neonate basking. Photo: Gabriel Evans-Cook
Blue racers are oviparous (egg-laying) snakes, laying an average of 15 eggs in early-summer that hatch in late-summer. Females require nesting sites that get plenty of sunlight throughout the day to incubate their eggs, and use habitat features such as rotting logs and stumps, mounds of decaying vegetation, large rocks, or animal burrows to lay their eggs within. To survive the freezing temperatures of winter, blue racers hibernate underground in bedrock crevices, mammal and crayfish burrows, tree root systems, and even human-made structures like old foundations. Snake hibernation sites, also known as hibernacula, need to be deep enough to allow them to reach below the frost line, while maintaining adequate moisture levels. These requirements are critical in keeping hibernating snakes alive by preventing them from freezing and from dehydrating. Like many other reptiles, blue racers exhibit fidelity to both nesting sites and hibernacula, meaning that they return to the same locations year after year.
The availability of suitable nesting and hibernation sites is critical for the persistence of the remaining blue racers in Canada, since these habitats are directly related to the population growth and survival. Unfortunately, habitats that meet their specific requirements are rare and due to their sensitivity to disturbance, are in increasingly short supply. Blue racers are listed as endangered in Canada and having been extirpated from the mainland, they are now only found on Pelee Island. To prevent further declines and support the remaining population, an important part of the recovery of blue racers in Canada is ensuring that quality habitats remain on Pelee Island.
As a part of the ongoing, collaborative blue racer project on Pelee Island, efforts to increase the amount of suitable habitat include the installation of artificial habitat features, led by Natural Resource Solutions Inc. (NRSI) and supported by 8Trees Inc.
Artificial Nesting Structures
From 2019 to 2020, snake nesting structures, also referred to as nest cages, were created and installed throughout the blue racer’s range on Pelee Island, consisting of wire mesh fencing formed into a cylinder and filled with materials like straw, mulch, leaves and sticks. To ensure that they provide adequate habitat for nesting snakes, NRSI has been monitoring the artificial nesting structures annually. Throughout the nesting season, thermal loggers are installed within nesting materials to ensure that they reach appropriate temperatures for snake eggs to incubate. In the fall, materials from each cage are removed and searched by hand for any signs of use by snakes, including eggshells, shed skins, and live snakes. No eggshells have been observed in the cage materials to indicate that snakes were using them to nest yet.
An example of a nesting structure on Pelee Island. Photo: Jennifer McCarter
To increase the availability of suitable snake hibernation sites on Pelee Island, artificial hibernacula were constructed by NRSI and 8Trees. These artificial hibernacula consist of deep cisterns within the ground, topped with soil and vegetation as insulation, and fitted with access tunnels to allow snakes access within. To ensure that each hibernaculum provides appropriate conditions for snakes to survive over winter, entrances to the hibernacula were kept closed for the first winter after construction (2020-2021) to prevent snakes from using them. During this time, temperature, moisture, and water level loggers were installed and extensively monitored. Conditions within the hibernacula were found to be suitable for overwintering snakes, and so entrances were left open for the 2021-2022 winter. Early in the spring of 2023, the artificial hibernacula were monitored for the emergence of blue racers, and monitoring will continue annually.
Though there has yet to be evidence that blue racers are using the artificial nesting structures and hibernacula, multiple species of snakes have located these habitat features and have chosen to be around them. It can take time for animals to find and grow accustomed to new habitats, and so hopefully more snakes will find and begin to use them in the future. Nesting site and hibernacula monitoring will continue.
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