If you have a phobia of snakes, you would be well advised to avoid the Narcisse Snake Dens of Manitoba, Canada. The name gives it away. This wildlife reserve is the winter habitat of tens of thousands of red-sided garter snakes (Thamnophis sirtalis parietalis).
These pretty snakes, with red spots and yellow stripes, are widespread across the northern United States and southern Canada. When the weather is warm, they live in mossy or marshy landscapes, where they feed primarily on frogs. Then, as winter approaches, they slither off to find a place to hunker down and hibernate.
The Narcisse Snake Dens, in the Rural Municipality of Armstrong, are a mixture of grassland and forest, covering a limestone bedrock. Over millions of years, water has seeped into the porous limestone, carving out deep crevices and caverns.
Several metres below the surface, these sinkholes are deep enough to lie below the frostline, but shallow enough to sit above the water table. In winter, when above ground temperatures routinely fall to -30oC, inside the sinkholes, it never drops below freezing. This makes the underground caverns the perfect spot for red-sided garter snakes to hibernate.
The snakes start moving into the dens in late September and early October and stay there for five to sixth months. There are four active snake dens here. With a combined total of up to 100,000 hibernating individuals, this makes the Narcisse Snake Dens the largest concentration of snakes in the world.
- How do snakes move? Despite having no legs snakes are amazingly agile
- How long do snakes live?
- How do snakes drink water?
Snakes rely on external warmth to fuel their metabolism, so whilst much of the natural world lies dormant in winter, so do they. Then, in spring, they emerge. If you love snakes, this is the time to visit. Males appear first, then females, all with one thing on their mind.
Females release a potent cocktail of pheromones, which are detected by the males’ vomeronasal organ, a specialised scent-detecting structure on the roof of the mouth. This guides the males towards the females.
Hundreds of males may congregate around a single female forming a writhing mating ball. Males attempt to rub their chin along the female’s spine and wriggle into alignment. When one succeeds, he inserts his of his two hooked ‘hemipenes’ into the female’s cloaca, depositing sperm and a gelatinous mating plug which then prevents other males from mating.
And, fact of the day, just as most humans are right-handed, most garter snakes favour the use of their right hemipenis. It’s larger than the left one and produces a bigger mating plug, suggesting it is preferred because increases the male’s chance of paternity.
