CELPIP Reading Part 3 Practice Test: The Snake Dens of Narcisse

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Each spring, a stretch of aspen woods and limestone in Manitoba’s Interlake region, north of Winnipeg, becomes the setting for one of the most unusual wildlife gatherings on the continent. At the Narcisse Wildlife Management Area, tens of thousands of red-sided garter snakes come up from underground over a period of a few weeks, sometimes in such numbers that the ground itself seems to move. Many naturalists consider it the largest concentration of snakes anywhere in the world. Garter snakes are not dangerous to people, and visitors who come to watch tend to be astonished by the sheer numbers rather than frightened by them.

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The snakes gather here because of what lies beneath the surface. The area sits on limestone bedrock that, over thousands of years, has been slowly dissolved by water, leaving cracks, sinkholes and underground chambers. These spaces reach deep enough to stay above freezing even during a prairie winter, when the soil nearer the surface freezes solid. Snakes cannot produce their own body heat, so finding a place where they will not freeze is a matter of life and death. Because places like this are scarce, snakes from a wide surrounding area travel to the same few dens each fall, where they remain inactive, packed closely together, for as long as seven or eight months.

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When the weather warms in late April or May, the males usually leave the dens first and wait near the entrances for the females. As each female appears, she may be surrounded by dozens of males competing for her, forming what observers call a “mating ball.” Males are smaller than females, which allows many of them to crowd around a single partner. Once mating is over, the snakes spread out into the surrounding marshes, where they spend the summer hunting, mostly frogs. Unlike many reptiles, garter snakes do not lay eggs; instead, the females give birth to live young in late summer. The newborn snakes are independent from the start and receive no care from their mothers. In early fall, the adults and their offspring make their way back to the dens.

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For years, the journey between the dens and the marshes took a heavy toll. Thousands of snakes were killed each spring and fall while crossing a nearby highway, and some researchers feared the population could not withstand such losses. In response, low fences were put up to guide the snakes toward tunnels built beneath the road, and drivers are asked to slow down during the busiest weeks. Today, a walking trail with viewing areas lets visitors see the dens up close, and they are asked to watch the snakes without handling or disturbing them. Signs along the trail explain the snakes’ yearly cycle.