For decades, snakes were believed to be solitary creatures, living and hunting alone. But research is beginning to tell a different story.
Some snakes mingle not too differently from other social animals around us. Butler’s garter snakes, for example, show a complex social structure sorted by age and sex, according to a November 2023 study published in Behavioral Ecology.
The most socially connected individuals were also among the fittest, which suggests that being friendly might have an impact on well-being. While these findings upend long-held assumptions, they’re made vividly real in one of the most extraordinary wildlife spectacles on Earth.
Every spring, at a limestone-riddled patch of Canadian wilderness called the Narcisse Snake Dens, tens of thousands of red-sided garter snakes surface in tangled, living knots—forming the largest snake aggregation anywhere on the planet.
These Dens Have The Ideal Hibernation Conditions For Red-Sided Garter Snakes
As a subspecies of the common garter, red-sided garter snakes, or Thamnophis sirtalis parietalis, range widely across North America. But nowhere do they face conditions quite like those in Manitoba’s Interlake region.
Here, winter routinely drops below –30°C, and snow buries the prairie for nearly half the year. For an ectotherm whose body temperature hinges on the temperature in its surroundings, that would be a death sentence.
But beneath the wind-scoured fields of Narcisse lies a subterranean sanctuary forged by time. The bedrock here is limestone—soft, porous and ancient.
Roughly 450 million years ago, this ground was the floor of a tropical sea teeming with marine life. Over eons, water dissolved the calcium carbonate, etching deep fissures and caverns into the stone. These underground sinkholes and crevasses stretch several meters below the surface—deep enough to stay below the frostline, but just above the water table.
For a red-sided garter snake looking to hibernate, it’s the perfect spot for the long nap—cold enough to slow metabolism, damp enough to prevent desiccation and protected enough to last through several months of winter dormancy.
At Narcisse Snake Dens, Male Snakes Court By The Hundreds
At first glance, the Narcisse Snake Dens look like little more than sinkholes punched into a prairie of dry grasses and stunted aspen. But in spring, they erupt with motion. Males pour by the thousands from the depths of the limestone caverns, coiling over rocks and one another in a slow-motion frenzy of courtship.
And then the females arrive.
This is the red-sided garter snake’s grand social season, a few weeks every year when anywhere between 75,000 to 150,000 individuals emerge to mate.
The most spectacular behavior at Narcisse is the mating ball — a single female buried beneath a writhing mass of up to a hundred males. Every male in the crowd competes to align their tails with the lone female red-sided garter snake for a chance at copulation.
But this is no ordinary competition. In fact, a June 1985 study published in the Journal of Comparative Psychology noted that male red-sided garter snakes are more stimulated by the presence of rival suitors than the female alone.
In this courtship melee, pheromones do most of the talking. Each female releases a potent chemical signal that male snakes detect using a specialized scent organ in their mouths—the vomeronasal organ—which guides them toward her, according to an April 2006 study in Chemical Senses.
Once contact is made, males rub their chins along the female’s spine, contracting their bodies in rhythmic waves, attempting to maneuver into alignment. If a male succeeds, he hooks his hemipenis into her cloaca, depositing sperm and a gelatinous mating plug that temporarily blocks other suitors.
Narcisse Witnessed Thousands Of Snake Deaths Every Year—Until Conservationists Built Tunnels
While Narcisse Snake Dens may host the largest gathering of snakes in the world today, it may not have been so if it weren’t for consistent conservation efforts and some much-needed tunnels.
For years, Highway 17 in rural Manitoba held a grim seasonal tradition—the slow, crackling sound of tires flattening thousands of red-sided garter snakes. Each spring and fall, as the snakes migrated between their summer marshes and winter dens, tens of thousands of snakes died trying to cross the two-lane road.
In the late ’90s, as many as 30,000 were killed as they made their way to the dens each year.
Then came the winter of 1999. An early, brutal cold swept through the Interlake, chilling the earth before tens of thousands of snakes could reach the warmth of their underground dens. They froze—curled beneath leaves, trapped in open terrain, inches from survival. The population plummeted.
That double blow forced Manitoba to reconsider what was at stake. This was the world’s largest reptile congregation, an ecological phenomenon unlike anything else on Earth.
Conservationists responded with engineering, building snow fences to steer snakes toward a network of six-inch tunnels under the highway. Researchers painted the walls with artificial pheromones to lure them through. And slowly, the death toll dropped to around 1,000 every year.
Today, thanks to decades of grassroots effort and a little chemical sleight of hand, the Narcisse Snake Dens are back to full strength. The red-spotted tide once again surges each spring with the cheers of visitors and the quiet satisfaction of those who refused to let it disappear.
Snakes like the red-sided garter snake are known to be great pets. How well do you connect with your pet snake? Take the science-backed Pet Personality Test to find out now.
