Narcisse Snake Dens in Manitoba boast the highest concentration of garter snakes in the world, with tens of thousands of them emerging from underground limestone caverns every single spring.

Why the snakes gather at Narcisse

The spectacle begins underground. Near Narcisse, Manitoba, the prairie’s shallow soil meets fractured limestone, where cracks and cavities provide deep, sheltered spaces for snakes to spend the winter. Garter snakes are cold-blooded, so they cannot keep their bodies warm through winter activity; they retreat below the frost line, packed together in dens that buffer them from the worst cold.

The dens matter because suitable winter shelter is scarce across the surrounding landscape. Several snake species use the same network of underground refuges, and large numbers return to them year after year. When spring warms the ground, the snakes emerge into the open at roughly the same time, turning a hidden winter gathering into a highly visible migration.

A brief, crowded race to mate

Males typically emerge first. As females appear, many males converge on each one, forming what is known as a mating ball: a writhing cluster in which males compete to mate with a female. The behavior is driven by reproduction, not aggression toward people. Once mating is over, the snakes disperse into nearby habitat to feed and spend the warmer months.

The timing makes the scene especially striking. Snow may still cover the ground, but the first warm, sunlit areas around den entrances can draw snakes out. Their dark bodies absorb heat, helping them become active in the cool spring air. A cold snap can slow activity again, so the busiest viewing days depend on weather as well as the season.

Why this is a place-specific spectacle

Narcisse is not simply a spot where many snakes happen to cross paths. The limestone landscape supplies a limited set of dependable winter refuges, and the snakes’ annual return concentrates them around those entrances. That geography creates both the dens and the brief spring gathering that visitors come to see.

The dens are also essential habitat, not just viewing sites: disturbing or damaging an overwintering refuge could affect snakes that rely on it across the entire cold season. The remarkable scene above ground begins with a much less visible fact—the same sheltered cracks in the limestone can protect thousands of snakes through Manitoba’s winter.