In the Canadian province of Manitoba, Narcisse Snake Den is a provincial wildlife management area located in the rural municipality of Armstrong. These nests are the winter home for approximately 100,000 red-sided garter snakes. These sinkholes are thought to be the largest concentrations of this species on Earth. Their winter refuges lie deep in caves carved out of water-smoothed limestone beneath the surface. When spring arrives, snakes emerge from these underground dens and gather in pits to mate. Once the breeding season is over, they gradually disperse into the surrounding marshes, where they spend the summer months feeding and roaming.
Narcisse Snake Dens: 100,000 snakes spend the cold winter here
According to BBC Wildlife, Narcisse Snake Den is located in the rural municipality of Armstrong, where meadows meet forests and the soil is porous limestone. At several meters deep, these cracks are below the frost line but still above the water table. This detail is important. Ground temperatures can plummet to -30°C in winter. Inside the cave, however, the temperature never drops below freezing. It’s the perfect winter refuge for the red-sided garter snake (scientifically known as Thamnophis Sirtalis parietalis).They start arriving in late September or early October. Sliding underground and gathering into tight clusters, they then wait for five to six months.
Why snakes rely on external warmth
Snakes rely on external warmth to fuel their metabolism. So when winter seals the land in ice, they stop functioning. Experts say that together they may help reduce water loss and stabilize body temperature. Males are reported to emerge first, usually while the snow is still clinging to the ground. They gather near the entrance to the nest. Female garter snakes release pheromones, which are chemical signals that the male detects with the vomeronasal organ, an odor-sensitive structure on the roof of the mouth. It leads them unerringly to the source. One female can attract dozens or even hundreds.The process that follows is called mating the ball. A group of writhing snakes, all vying for position. It looks like a single, pulsing organism. Visitors step back. The camera is out. Somewhat obsessed. Some people are clearly rethinking their life choices. The male rubs his chin against the female’s back in an attempt to adjust his body. When one succeeds, he uses one of his two hook-shaped reproductive organs, called a hemipenis, to transfer the sperm. A gelatinous mating plug is left behind, which appears to reduce the chances of competitors mating with the same female.
Red-sided garter snake facts
- venom: The red-sided garter snake is nonvenomous and generally harmless to humans, but it can be surprisingly brave when cornered.
- size: Adults usually grow to about three or four feet in length, are stocky, and have an olive-brown to almost black body.
- color: Most people have clear yellow stripes on their backs, while stripes on the sides may look clear or blurry, depending on the individual. The yellowish belly often shows a dark edge along the scutes. The famous red stripes on the sides may appear between or spread across the scales, giving each snake a slightly different appearance.
- scales: They have 19 rows of keel-shaped scales and are ovoviviparous, meaning the female gives birth to live young rather than laying eggs. Newborns are similar to adults in being smaller, but just as varied.
- Habitat: They are found near ponds, swamps, canals, or slow-moving bodies of water, where they feed primarily on amphibians, but also worms and the occasional small rodent.
