#16: Dancing with the Snakes
Click here for print friendly version Page 1 of 2
In the first weeks of May, the porous limestone country north of Winnipeg, Manitoba, becomes the scene of greatest orgy in nature, as thousands of red-sided garter snakes emerge from their winter dens and procreate in huge, writhing mating balls. All garter snakes den communally, but this is the largest gathering of snakes on the planet, the only place where you can take in ten thousand at a glance. It is an anachronistic expression of the riotous abundance of life that once proliferated, comparable to the mile-long clouds of pierid butterflies that you can still be enveloped in along the Congo River, and particularly heartening because snakes have always been the most persecuted group of animals.
My eight-year-old son, Zachary, belongs to seven generations of naturalists, going back to Russia in the l830s. Most of them were lepidopterists; Zach is the first to exhibit a deep fascination for reptiles and amphibians. Part of this undoubtedly has to do with Steve Irwin, the fearless, boundlessly enthusiastic Australian “crocodile hunter” on t.v., whom Zach and his two brothers and millions of other kids are devoted fans of. But Zach possesses a remarkable empathy for other forms of life that I have encountered in only a few people in thirty-five years of writing about the natural world and those who study it. I’ve learned a lot from him about snakes, salamanders, frogs, and turtles-- subtly beautiful creatures I had never paid much attention to, watching him turn over rocks in Montreal’s Mount Royal Park, which we live on the edge of, and uncover hundreds of red-backed salamanders, or net aquatic forms of red-spotted newts in ponds around our country place in the Adirondacks. Turning up a corn snake on a Vermont farm, a western diamondback on an Arizona ranch within minutes of his arrival on the scene, Zach has shown me that reptiles and amphibians are far more ubiquitous and omnipresent than I had suspected, even with the assault they are under from so many quarters.
Zach’s mom, my wife, grew up in a village in Uganda, where a spitting cobra once slithered into her hut, and flying snakes took off from the tips of tall grass and caught small birds in mid-air. Like many people, she is terrified of snakes, and it took months of pleading by Zach before she finally agreed to let him have a pet snake, a rough green snake, whom he named Minty. Minty was maybe twenty inches long, impossibly thin, and totally docile. Zach posed for our latest Christmas card with Minty curled around his fingers. But one morning a few months later, Zach found Minty dead in his terrarium. There had been no indication anything was wrong with him. Zach was inconsolable. To cheer him up, I decided to take him to see the snakes in Manitoba.
Their sexual frenzy usually peaks around Mother’s Day, but this year it was taking longer for them to come up from their subterranean hibernacula, the lack of insulating snow cover over the bitterly cold winter having driven them further down, and the bacchanal was only just getting underway when we arrived on Victoria Day weekend (the Canadian equivalent of Memorial Day weekend), a week later.
Flying into Winnipeg, we headed north up into the interlake region, between Lake Manitoba and Lake Winnipeg, most of which is dead flat, like most of the province. Only scattered copses of the original aspen parkland remained, like little islands in a sea of wheat and flax. After an hour or so, the soil got noticeably thinner. Cattle were grazing in rocky pastures, and in places the limestone bedrock was exposed. We could see scratches on it from the immense glaciers that had slid over it ages ago and brought down granite boulders from hundreds of miles to the northeast. The deeper gouges were filled with finger lakes, swamps, and marshes full of frogs. This was great habitat for snakes, but not for humans, and like most of rural Manitoba, and the interlake region is losing population. The dens are near an old Jewish colony called Narcisse, which only lasted from l903 to l914 and was abandoned after the railroad passed it by. All that is left of Narcisse is its graveyard, which is kept up by one of the descendants of the nineteen families who emigrated from Ukraine; he owns big malls in Winnipeg. Chatfield, the next settlement to the north, is down to nine full-time residents. So it is safe to say that the greatest vertebrate biomass in the r.m., or rural municipality, of Armstrong, which Narcisse and Chatfield are in, is not human, but reptilian.
Four of the dens, containing an estimated fifty thousand snakes, are in the fifteen-thousand acre Narcisse Wildlife Management Area, which was created from the Nariccse communal pasture in l982. We rendezvoused there with Bill Preston, the emeritus curator of herpetology at the Manitoba Museum and the author of The Reptiles and Amphibians of Manitoba. Bill has been visiting the dens for forty years and was instrumental in getting them protected. “When I first got here,” he recalled, “there was a guy named Pikowski who collected the snakes for biological supply houses, and native Ojibwa snake-pickers would set down sheets of tarpaper in ditches overnight, and in the morning hundreds of snakes would be warming themselves up under them. Many of the biggest snakes were shipped to the States, where they were sold to pet stores and dissected in high-school and college labs. We had a meeting at the museum, and got the province to limit collecting to only in the fall, then we got it stopped altogether and the four most productive dens annexed as provincial crownlands.
Why is Manitoba, at the northern limit where reptiles can live, so congenial to garter snakes ? I asked. Bill attributed this to the combination of the karst topography providing roomy chambers for them to den together in, and the availability of an abundance of frogs. The winters here can go down to fifty below Fahrenheit, but the caverns stay forty degrees above year round. But the snakes also den in shaley cliffs, and in the granitic Precambrian shield, to the east. Fifty dens are known in the province, but there are undoubtedly many more.
The red-sided garter snake, Thamnophis sirtalis parientalis, is one of thirteen subspecies. Its lateral lines vary from pink to orange to yellow; the top line is usually yellow, but not always. How the colors vary from den to den and relate to predation and mating success is under study.
Dian Neuman, a young interpreter with the provincial conservation department, took us to Den 3, a sinkhole (where one of the underground chambers had collapsed) on whose floor dozens of snakes were probing their way among newly leafed-out burdock and stinging-nettle plants. Some had formed wriggling balls. “So far it’s been more of a trickle than a flood,” Dian told us. The den was fenced off, to keep schoolchildren from going down into the pit and stomping the snakes, which used to happen. Now schoolchildren across Canada are taught that May is snake emergence month, and are assigned essays to write about the importance of helping the snakes get across highways as they disperse to their summer range. Some of these snakes had already climbed the walls of the sinkhole and were making their way into the woods. Zach was in seventh heaven, almost in a trace, picking one after another up gently and unhesitatingly and holding it for a while before placing it back in the grass. The snakes were totally docile; this is the place for someone with a phobia about snakes to come and get over it. “I have never caught so many snakes in my life,” Zach exclaimed. “This is the most wonderful thing that has happened to me. I wish you good luck and hope you don’t get eaten or stepped on or run over,” he said to one that Dian identified as a female. The females are longer and thicker. Some have the girth of a loonie (a Canadian dollar coin) or even a toonie (a two-dollar coin). Unless they are gravid, their tail bases taper more abruptly than the males’, whose thicker tail bases house their hemipenes, or paired copulatory organs.
The vast majority of the snakes we were seeing were foot-and-a-half-long, year-and-a-half-old males. The males emerge first, in great number, and heating themselves up in the strong spring sunlight, wait for the females, who emerge singly, nervously, exuding attractive-smelling pheromones. Most of them are quickly mobbed by the males. Up to two hundred males will vie for the chance to penetrate them. We saw several dead females who had been smothered in the melee. Some females manage to run the gauntlet of the males and to sneak off to safety. Some are chased up into bushes or trees, where the bigger males are lying in wait for them. We saw several saskatoon shrubs, in white flower, englobulated with mating balls, dripping with snakes.
After inseminating the female, the successful male plugs her with
gelatin secreted from his liver, which soon hardens, and she emits different,
unattractive pheromones. The other males leave her alone, and she makes
her way to the summer range, along with other inseminated females,
and ones who have eluded the males and will meet up with boyfriends later,
in less stressful circumstances, and smaller males who have little chance
of squirming and muscling their way up to the female in a mating ball.
Heading for the swamps and marshes at the top speed of a person walking,
they feast on wood frogs and boreal chorus frogs. The imperative is now
to eat. Each snake has lost ten percent of its body weight over the winter,
Dian explained, and has been losing another one percent a day since it
emerged. But many don’t make it. Some are caught by crows, hawks, seagulls,
bald eagles, thirteen-striped or Richardson’s ground squirrels. Others
are run over by cars and trucks.
We saw several dead snakes whose livers had been pecked out by crows. Seagulls were wheeling and crying in the air. You’d think there would be a feeding frenzy at the dens, and some do experience massive predation, but not these; apparently the birds find the newly emerged snakes still too cold for their liking.
Even with all this attrition, enough females make it to the swamps, where they bear up to twenty live young (garter snakes are ovoviviparous, as opposed to oviparous), which they have nothing further to do with. The gelatinous plug falls off, and the females mate again. One brood can have several fathers, but the female has young only every two years. She can store the sperm, sequestering it over many ovulation cycles yet still keeping it viable, before she finally gets pregnant. Dian said that one female in a lab had young seven years after her last contact with a male ! The young snakes spend their first winter at the summer range, in anthills and other warm places, and in their second fall, they return to the dens with the others.