NARCISSE -- Tens of thousands of garter snakes here are slipping out of their subterranean winter homes sooner than usual to meet and mate.
An early spring has sped up the annual orgy north of Winnipeg that occurs before the snakes slither off to wetlands to fatten up over the summer.
People from all over the world converge on the snake dens at Narcisse to watch the spectacular rite of spring.
Ingo Heinrich of Cologne, Germany, was fascinated by the thousands coming up out of the ground Monday.
"It's nice to see the smaller snakes and to see a lot," said Heinrich.
He got lucky there, this year.
Normally, the snakes don't come out of their limestone caves below the frost line until the last weekend in April or first week in May, said wildlife biologist Dave Roberts with Manitoba Conservation.
"They're a week to two weeks early," Roberts said Monday, overlooking snake den No. 3, the most active so far. He expects more snakes to come up to the surface at the other dens to mate over the next three weeks.
This year, researchers from Oregon to Brazil and media outlets from as far away as the United Kingdom are taking in the action at the Narcisse snake pits.
Spring is mating season, when the dens become a mass of hissing, swirling tangles of garter snakes.
Studies of the snakes' sex lives and strategies are revealing, Roberts said.
Females, who reproduce every two years, give off a pheromone indicating they're ready to mate when they leave hibernation that attracts males who literally swarm them. Once they mate, the females are injected with a pheromone that makes them unattractive to males. They go off in search of wetlands to eat minnows and toads and fatten up for the winter -- and to look for bigger and better males to mate with, Roberts said.
"Their babies can be sired by more than one male," he said.
The females are equipped with something like a portable sperm bank that they carry around with them until they're fat and healthy enough to produce eggs, he said.
"If there's a drought, she may not ovulate."
Researchers are looking at whether female snakes who mate in the den when they're swarmed by males have as many offspring as females who mate in the bush where they have more choice in their mate, he said.
Scientists have already learned some male snakes will give off a hint of the female pheromone to attract males. The male snakes will rub up against him to warm him up then he will go after a female and engage her in mating more quickly because he is so warm, he said.
Once they've mated, they'll travel up to 20 kilometres to wetlands and spend the summer feasting on minnows and toads and having their offspring. In the fall, they follow their pheromone trail back to the cosy dens at Narcisse before it gets cold. "There's an overwhelming desire to get below the frost line," Roberts said.