Places

Snakes on a plain: Manitoba’s Narcisse Snake Dens 

Each spring, a disquieting tangle of tens of thousands of gartersnakes emerges from their winter home, forming the world’s largest gathering of snakes 

The Narcisse snake dens protect the largest aggregation of red-sided gartersnakes on the planet.
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At 11:00 a.m. on a preternaturally warm day in May, the rock-strewn parking lot on the eastern edge of Manitoba’s Narcisse wildlife management area is filling up fast. Families unload strollers, coolers and other leisure paraphernalia as a convoy of vans from a Winnipeg seniors care facility pulls in, followed by a bus seeping the muted squeals of excited schoolchildren. Groups hurry down a short trail to stake out territory at a cluster of picnic sites, each featuring a table partially enclosed by an L-shaped windbreak of wood set perpendicular to a large slab of local limestone stood on end, Stonehenge-style.

Map: Chris Brackley/Can Geo; Map data: Garter snake range data 2023: The IUCN Red List of Threatened Species. Version 3. www.iucnredlist.org. Downloaded on Dec. 12, 2023.
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Though it surely ranks among the world’s oddest-themed picnicking sites, the reaction of many a visitor to the park’s raison d’être makes the notion of eating first and seeing the sights later odder still. For beyond these convivial tables, a post-prandial stroll along a three-kilometre loop through grassy alvars and stands of dwarf aspen delivers diners to a sight that — fascinating though it may be — is for some disconcerting: the Narcisse Snake Dens, where a fluctuating population of around 75,000-150,000 red-sided gartersnakes overwinters in limestone sinkholes and, after emerging in spring, spends several weeks vigorously mating under a Prairie sun. The planet’s largest aggregation of snakes, it is observed by some 35,000 people each year, close enough to have the amorous animals slither over their shoes or be picked up by the more intrepid.

Depending on who you are, this de facto Wonder of the Natural World is a scientist’s dream, bucket-list Instagram brag or, for those addled by the thought of even a single serpent, serious trigger-fodder. Yet regardless of where one fits on the spectrum, all leave Narcisse with two important gifts: a first-hand, David Attenborough-free recalibration of nature’s “wow” factor, and newfound respect for these mostly misunderstood creatures.

A mating ball forms in the snake pit. When a mating ball breaks up, it resembles a chaotic high-speed fission, firing ribbons in every direction.
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Another certainty about the sight of thousands of cold-blooded snakes spaghettiing in a rocky pit in the cold-hearted north are the questions it engenders: Why so many? Once the answer of “mating aggregation” lands, more inquiries follow: Why here? Where do they come from? How long are they underground? Aren’t they hungry? How do they find a mate? What do size differences mean?

These logical queries, sounded by curious visitors, are identical to those posed by scientists for whom Narcisse has long been a biological goldmine, from which nuggets of data on everything from homing to reproductive ecology to behavioural neurophysiology are continually panned.

A lone male emerges curiously from the undergrowth to slither toward the camera.
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I’ve visited several times over the years, beginning as a young graduate student loosed from the Royal Ontario Museum one spring to collect salamanders in Manitoba. For a herpetologist (someone who studies reptiles and amphibians) based in Canada, pilgrimage to Narcisse is a rite of passage. And not just because gartersnakes — by dint of being harmless and found in every province — are a literal carnet for any Canuck kid with scaly interests. It’s more about unspoken pride that the only place on Earth where this number of reptiles can be seen in one go is a frosty wedge of the Great White North.

On that sojourn, I’d been struck first by the dens’ relative anonymity. If an attraction based on snakes was in, say, the decidedly snakey southern United States — billboards would hector you in from all directions for a hundred kilometres. There’d be souvenir stands and cheesy motels, fireworks warehouses and roadside pie stands. Instead, with only the occasional tiny, monochromatic Manitoba Transport sign as compass, I hadn’t been sure I was headed the right way until, from the corner of my eye and far off the highway, I’d spotted two cartoonish, intertwined, 10-metre gartersnakes — known as Sara and Sam — in the town of Inwood.

It is a little different this morning. My travelling companion is Randy Mooi, curator of zoology at the Manitoba Museum, and after craning our necks to catch Sara and Sam, we veer right out of town into a monotony of scrub forest and farm field. With the only directional reinforcement a steady increase in road-flattened snakes (we’ll get to this), many kilometres pass before a large sign announces the Narcisse Snake Dens. It’s a literal middle-of-nowhere, but we have plenty of company.

Hustling past the picnic-area mayhem, Mooi and I light out for the first of four dens linked by trails. Amazingly, at Den 1, there’s no one save us and some 50 snakes. It’s both early season and early in the day, but the dens’ signature phenomenon is already forming: a mating ball. A single large female is surrounded by a dozen smaller males, wound around her like strands of hemp rope.

The Mother’s Day crowd at Den 2.
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The red-sided gartersnake is one of a dozen recognized subspecies of the common gartersnake, a continental superspecies ranging from the Atlantic to the Pacific, Mexico to the sub-Arctic. Red-sided gartersnake males average 40-60 centimetres and females, 60-80 centimetres (though they can reach 110 centimetres). The den is surrounded by snake-friendly chain-link fencing to keep overly curious humans from disturbing the proceedings — or falling in. A wooden viewing platform stretches out over the pit, where we contemplate the fortuitous reasons for these annual gatherings.

That such a profusion of snakes occurs this far north may seem strange at first blush, but makes sense in the details. While summers here are warm enough to accommodate a number of reptile and amphibian species, winters are long and harsh, with surface temperatures far south of -30 C for extensive periods and frost moving deep into the ground. For ectotherms like snakes, whose body temperature remains close to air temperature, decent hibernaculae are at a premium — they must be below the frostline but above the water table, yet humid enough that snakes won’t dry out over the seven to eight months they spend in them. The Narcisse area features classic karst topography, where surface water and rain have dissolved calcium carbonate along weaknesses in the limestone bedrock, creating deep fissures and underground chambers. These chambers often collapse in on themselves as sinkholes, allowing snakes access to an extensive labyrinth several metres below the surface.

Fascinated visitors watch the snakes from a viewing platform at Den 3.
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The limestone is ancient, composed of creatures whose skeletons accumulated at the bottom of a tropical sea some 450 million years ago. But the karst landscape is more recent, a legacy of Pleistocene glaciation that scraped the land clean and, in its final throes 11,500 years ago, spawned Lake Agassiz, one of the largest freshwater lakes ever known. Agassiz’s remnants include Lake Winnipeg and the Winnipegosis/Manitoba complex of lakes, which bracket the Interlake Region, as well as surrounding water bodies. 

As shallow Agassiz scions like Lake Winnipeg shrank, the draining water not only helped create the karst formations but left extensive marshland pooled across the flat landscape — a giant buffet of worms, frogs, fish and small mammals for generalists like gartersnakes. Only a few thousand years ago, critical sinkhole dens and prime summer marsh habitat were adjacent, but retreating lake margins and, eventually, shrinking marshland required snakes to make ever-more-extensive migrations between the two. In the 1970s, while pursuing a doctorate at the University of Manitoba, celebrated Canadian herpetologist and gartersnake doyen Pat Gregory found that some snakes travelled almost 20 kilometres to summer habitat, then made the return journey to dens in fall. Here, they gather to sun until cold drives them deep into the limestone. In late April and early May they re-emerge, males first, followed a week or so later by females, whose arrival is the reptilian equivalent to Ladies Night, with all hell breaking loose among eager males milling at the sinkhole bar.

The mating-ball frenzy, in which mobbing males attempt to vigorously rub chins along a female’s back, suggested to scientists that females must exude some kind of sexy snake appeal. In a landmark 1989 paper in Science, Oregon State University’s Bob Mason identified a skin lipid produced by female red-sided gartersnakes as the first pheromone (an externally secreted hormone that transmits information to members of the same species) known in a reptile.

Interpreter Gary Chikousky.
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Mason — whose name is now synonymous with this giant, self-contained outdoor laboratory and who is fond of mentioning he met his wife “in a snake pit” when she joined his 1997 Narcisse fieldwork as part of a citizen-science ecotourism group — continues his voluminous research with a stable of graduate students to this day. Among their many startling discoveries: not only can sex be differentiated by pheromones, but so can breeding versus non-breeding body condition; males prefer larger females, whose pheromones are more attractive; males can differentiate female pheromones from different dens and prefer those from their own; some males produce female pheromones to fool other males and gain warmth and protection within mating balls (in experiments, female-performing males warmed to 28 C would cease impersonating females, while males whose body temperature remained at 10 C kept up the pheromone drag show). All this sensory showmanship comes courtesy of snakes’ ability to detect sexual, prey and same-species scents at mere parts per million — the reason for the constant flicking of their tongue, which delivers airborne molecular cues to the sensitive vomeronasal organ in the roof of their mouth that detects scents. 

But while scientists inform much of what we know about the biology and behavioural ecology of these snakes, there’s plenty of nature on display for visitors to get their own sense of how the snakes fit into the larger ecosystem. “This trail is usually littered with de-livered snakes,” remarks Mooi as we stroll toward the second den, referencing the favoured snack crows extract from easily caught serpents. “But then, we’re early.” 

Recalling the fastidious re-creation of a snake den in the Manitoba Museum that Mooi showed me yesterday, replete with a hungry crow lurking in an aspen, begs a question: what is the value of an actual visit? “The dens provide huge opportunity for learning about all sorts of aspects of ecology,” he says. “In a day and age where it’s harder and harder to find natural experiences because we’ve surrounded ourselves with concrete, something relatively close that you can bring a school group to opens up whole new worlds. Kids can also learn how this is a professional opportunity — that they could grow up to study these kinds of things for a living.” 

A mating ball of snakes clings onto a branch.
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Only a half-kilometre distant, Den 2 is a completely different story from the first den.

We’re within sight when smallish snakes rush the path. Like grass blades fluttering flat in a strong wind, threads of desperate males hard on the scent of a female fire off in waves, oblivious to our presence. From the viewing platform come screams, groans and all manner of exclamation as kids and adults alike make first visual contact with a three-metre-deep sinkhole carpeted with thousands upon thousands of wriggling snakes.

This is more like it.

Dispersed in great, Medusan clumps, snakes cover the floor, hang from fissures and holes, and drape over rocks and branches. Smaller aggregates ply the sinkhole’s edges, and care is needed to step anywhere as snakes whip across startled feet and pop bug-eyed heads from cracks in the viewing platform to swivel like prairie dogs. There’s no avoiding the subject, no distant viewing opportunity through binoculars, no chance to be anything but among and within. Remember the movie Snakes on a Plane? A campy joke of mostly CGI snakes that reflects zero biological reality? Forget it. How about the “Well of Souls” snake scene in Raiders of the Lost Ark? Closer, but multiplied several thousandfold with you in it.

“Gross!” from up ahead. “Eeeeeek!” from another quarter, perhaps the only time outside a comic book you can justify such a spelling.

“Wow — cool!” from a boy whose father physically restrains him from going over the rail.

“Oh my,” moans a woman just to my right, holding a hand to her forehead.

“What do you think?” says her friend.

“Well, it looks pretty much like I expected. I just hoped it wouldn’t.”

Depending who you are, this de facto Wonder of the Natural World is a scientist’s dream, bucket-list Instagram brag or serious trigger-fodder.

The crowd at the rail eventually dissolves to reveal a young girl named Gabi who practically glows with wonder, the little snake wrapped around her arm calmly soaking up both warmth and adulation. “Snakes have always been my favourite animal,” she says. And, lest I dismiss her apparent longstanding ophidiophilia as the hyperbole of an eight-year-old, “she’s actually waited four years for this,” adds mom. The Winnipeg resident first promised her snake-charmed child a trip to Narcisse in 2020, but the pandemic closed the site that spring; ditto 2021, while severe flooding in 2022 discouraged visitation. But Gabi’s dream has finally come true, and she’s making the most of it.

In another visiting family, the younger of two tween girls is terrified by every snake she sees, shrieking as the creatures streak past on all sides. “I’m good,” she says, backing away  every time her sister urges her to join her at the rail. When her brother says, “there’s one behind you,” she literally jumps. He picks it up, calms it down with gentle handling and passes it to her sister. Even mom briefly holds it, though she has to close her eyes. “OK,” the mom says to the petrified daughter once it wriggles free. “Let’s go to the next den to walk off your anxiety.” 

The family’s patience pays off. At Den 3, where snakes clump in rocky crevasses, on a limestone ledge, beside a log and in a bush — places where females are trapped by a frenzy of males — dawning realization that these animals are going about their business unconcerned with her noticeably calms the girl. By the end of a long stint at Den 4, for a nanosecond, the molecules of her fingertip come close enough to a snake held by her sister to claim — at least by the laws of physics — to have actually touched it. “You’ve come a long way in an hour,” laughs mom. 

A significant mortality factor for the red-sided gartersnakes is vehicle collisions when they try to cross the highway.
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Given humans’ generally negative association with snake dens (historically, we’ve dynamited, burned and filled them, and still use the phrase “den of snakes” to describe any worst-of-the-worst group of humans), a lot of people come a long way here. Beside us, a young, initially trepidatious boy is now naming every lone snake that crosses the platform. “Bye Skittles!” he calls as his latest pet-for-a-second glides off into the underbrush.

“You better have a lot of names ready,” Mooi advises. “Because you’re going to see a lot of snakes.”

“The best for me is seeing people turn like that,” says interpreter Gary Chikousky, who has been watching with us. “A busload of kids arrives, and probably half of them don’t really want to be here, you know, saying ‘Why do we have to go to this stupid place?’ or begrudging it in some other way. But then they see something they didn’t even imagine and get interested. And by the time they leave, they’re enjoying themselves, naming snakes and learning without knowing it.”

When Chikousky moved to the Narcisse area from Winnipeg to farm cattle, he’d never heard of its local snake dens. But once he retired, they provided a spring job he’s looked forward to for 20 years. In his time as an interpreter, he’s seen everything, taking the good with the bad and weighing in where and when he can. Grizzled, with a close-cropped grey beard, he seems as unflappable as 450-million-year-old limestone, easily answering any question thrown his way.

“How long do they live?”

“Fourteen to 16 years in the wild, up to 25 in captivity. The problem for snakes is they grow continuously, so the oldest ones are bigger targets for predators.”

“How many snakes are actually here?”

“The estimate fluctuates between 75,000 and 150,000. There’ve been low numbers for five or six years now, but this year they seem to be bouncing back.”

As cold-blooded creatures, gartersnakes need the spring sunshine to emerge from their winter dens. By all accounts, 2023 wasn’t a great year for snake viewing, but numbers seem to be back on the upswing.
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It wouldn’t be the first time the Narcisse snakes have made a comeback. In 1987, as an aspiring provincial wildlife biologist, Dave Roberts moved from Winnipeg to Gimli, regional headquarters for the Interlake Region. At the time, the dens were in ecotourism infancy, today’s parking lot a gravel quarry. Visits, while not prohibited, were a difficult-to-access free-for-all that included snake-hunters who ransacked the dens, selling thousands of snakes to biological supply houses. People familiar with the site helped convince the provincial government to add it to the pre-existing Narcisse wildlife management area, and Roberts began the process of organized visits, overseeing a few staff each spring and — as funds became available — developing trails, interpretive material and the picnic area.

Originally a reservation-only guided tour, significant interest in the dens and the impossibility of stopping those without reservations prompted a switch to open access, with staff keeping an eye on things and answering questions. “But it grew beyond what we could successfully manage on busier weekends, and people were way harder to handle than we were capable of, which made staff difficult to keep,” Roberts recalls.

Narcisse interpreters have plenty on their plates: they’re also responsible for cleaning washrooms and waste management. Despite abundant waste receptacles, they still haul bags of garbage from the more popular dens that include cigarette butts, candy-bar wrappers and lens caps. “I had a new one yesterday — went down into Den 2 to get a lady’s credit card,” says Chikousky. 

It’s de rigueur to take mom, beleaguered by her own reproductive spoils, to watch snakes mate. 

I’ve seen the challenges interpreters face first-hand, including the mishandling of snakes — for example, kids squeezing too hard and parents getting pissy when staff try to gently intervene. One day I found myself behind a group carrying a snake between two dens with seemingly no idea they were displacing an animal that had been where it was for a reason (snakes have high fidelity to the same den). A kilometre journey for an animal this size is equivalent to 10 kilometres for a human.

I recall this tableau when Roberts alludes to the double-edged sword between promoting ecological values to the public and having the place swarmed. “We talk about how important this spectacle is, but we don’t really even know how many snakes are here or precisely where they all go in summer — it’s just kind of assumed they’ll be here forever. These are things [government] should put money and resources into understanding but hasn’t.”

When governments actually value the nature they’re purporting to protect, it directly contributes to public appreciation and stewardship. “When you grow up with something like this in your backyard, it’s hard to know how special it is,” Mooi told me. “But familiarity can also be good because repeated visits allow people to develop a healthier attitude toward snakes — even if they don’t quite grasp how special the phenomenon is.” 

An older sister carefully hands a snake to her gleeful sibling at Den 2.
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Dealing with the dens was supposed to be 10 per cent of Roberts’ time but most years took up a lot more. “For better or worse, I also became the regional snake guy,” he says. “If anyone had one in their basement I’d get the call. Then came the tunnels and fences.” Around the new millennium, the dens’ ecological importance was becoming better-known and people were taking more interest in the environment and conservation. It all fed into a desire to deal with a perennially upsetting problem: the mortality of snakes crossing Highway 17—particularly as they returned to dens in the fall when, according to a report Roberts wrote in the late ’90s, some 30,000 were killed each year. In a joint project between Manitoba Hydro, Manitoba Conservation, Manitoba Highways and local organizations, tunnels bored beneath the highway roughly every 100 metres over a kilometre-and-a-half stretch were fitted with pipe passages and low drift-fences to encourage snakes into them. Since snakes don’t like cold, dark tunnels, it could have been an expensive but ineffective gesture if it weren’t for Bob Mason. In an applied-science conservation collaboration, Mason put his Narcisse research to work by painting the tunnels with synthetic red-sided gartersnake pheromone to entice the animals to travel through. The snakes responded; fortuitously, they also left more pheromone along the way, compounding an effectiveness that saw the road toll drop to 1,500 per year. 

When the system was first installed, some 25,000-30,000 snakes used the tunnels during fall migration. “I’d put a box trap at a tunnel in the morning and come back in the afternoon and there’d be 300-400 snakes in [it], so we were having significant success in reducing mortality,” says Roberts.

Protecting the snakes remains an uphill battle. Snowmobiles and snowplows damage the fence each winter, requiring extensive annual repair. Other initiatives have waned. At one time, “snake-crossing” highway warnings were erected and taken down annually. “Not many people slowed,” recalls Roberts. “And most locals didn’t care, so the highway department flat-out refused to lower the 100 kilometre-per-hour speed limit. That was frustrating.”

The embattled fence remains an issue — every hole and downed section a potential death for hundreds of snakes. As any good road ecologist would advise, Roberts would like to see a more permanent tunnel-and-fence system. “Before I retired, I provided a highways biologist with a drawing of what they could do based on what I’d seen elsewhere in North America. If they ever redo that highway — not a priority because few people live out there — maybe that could happen, but it’s unlikely.”

Roberts believes the Narcisse snake dens should have been an ecological reserve in which no one was allowed, but a decision was made early on that it would be a place for public interpretation. “That’s been successful, but the downside is the population has been impacted by the cumulative effect of everything going on there. We’ve never really done enough.”

Interpreter Brandon Stuebing gently shows a gartersnake to a curious group of children.
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By far the busiest day (and perhaps the strangest) at the Narcisse Snake Dens is Mother’s Day. A traditional outing for many Winnipegonians, it’s a far-fetched scenario on a continent where pancake breakfasts and visits to botanical gardens are the norm. Here, however, it’s de rigueur to take mom, beleaguered by her own reproductive spoils, to watch snakes mate.

I’m here solo because Mooi’s colleagues have told him to avoid Mother’s Day at all costs, and I can see why—by 10 a.m. not only is the parking lot overflowing, but vehicles line both shoulders of Highway 17 for a kilometre. I head directly to Den 2 where, with the temperature already closing on 20 C, the ground is literally alive with males, females sight unseen. The snakes seem extraordinarily busy, perhaps following trails from the previous day’s activity given the blinding power of the female pheromone. As one of Bob Mason’s graduate students remarked: “If you handle too many females, the males will try to court your hand.”

I run into Gary Chikousky and ask, why Mother’s Day? “It started as a way to give mom some time off,” he says. “This place was close to the city and kid-friendly, so dad brought them out here for a few hours. But then about 10 years ago, something flipped and it was the whole family — mom, grandparents, dogs.”

As we speak, people around us are having photos taken with snakes, interpreters, signs — anything. It’s the Instagram generation and this place is as ’Gram as it gets.

Still, there’s a depth to nature here that the sheer spectacle of a Mother’s Day crowd denies, and I experience it that afternoon as the park shuts down. Once the people leave, the birds move in; a hawk flies down the path with a snake clutched in its talons; a happy crow hops across the tarmac with a freshly flattened snake in its mouth. And the snakes? They notice nothing, addled by hormones, sliding through a cycle thousands of years in the making — sleep for eight months, mate for two weeks, make a trip to the marsh and back, then do it all again. And maybe, just maybe, somewhere along the way a girl named Gabi falls in love with you long enough to learn something. 

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