Crawling through a writhing pit of 75,000 snakes may not be everyone's idea of a great day at work, but it was for Paul Colangelo.

The National Geographic grantee recently gained new appreciation for the reptiles while photographing the world's largest gathering of snakes in the Narcisse Snake Dens of Manitoba, Canada (map).

Each spring, masses of red-sided garter snakes congregate inside limestone caves to form mating balls, in which up to a hundred male snakes vie for a single female. She, in turn, "is desperately trying to get out of the pit," said Colangelo, an environmental documentary photographer.

These slithery swarms appear to be a "frenzy, but a closer look reveals a much finer dance," Colangelo said in his field notes. "The small males court the larger female by rubbing her head with their chins and maintaining as much contact between their long bodies as possible."

To Colangelo, getting up close and personal with the oft-feared reptiles can show people that snakes are fascinating, underappreciated, and even, he'll admit, a little cute. They have "puppy-dog eyes—they just don't blink," he quipped. (Also see "Year of the Snake: The Serpent Behind the Horoscope.")

We caught up with Colangelo to learn more about his snake-mating adventure.

How did you decide to do this project?

When I first heard about the largest concentration of snakes in the world in rural Manitoba, [my reaction was,] "That's the last place I would think something like that would happen." The winters are -40 [Fahrenheit/Celsius]. It's just so intriguing. I wanted to go and take a look.

It's not very well known outside of the snake world, but [Narcisse] does get a decent number of tourists, around 3,000 to 4,000 people a day [during mating season]. People come in from California just to do this—it's kind of a niche interest. (See "Wild Romance: Weird Animal Courtship and Mating Rituals.")

Why is this the largest gathering of snakes? What attracts them?

This grouping of red-sided garter snakes has the most northern range of any reptile in the Western Hemisphere. It's due to a lucky coincidence of two geological features: limestone crevices and marshes. It's a fantastic place for snakes to be in the summer because there are huge marshes loaded with frogs, but in the winter it drops down to -40. The only reason all these snakes can survive these winters is because of the large limestone crevices that reach deep into the ground, below the frostline. They spend about eight months of the year in these large underground chambers. They come out in the spring, mate in these dens and [then travel] up to 20 kilometers [12 miles] to their summer grounds, load up with amphibians and worms, and head back to the cave. (See National Geographic's pictures of snakes.)

What was it like being among all these mating snakes?

I was indifferent to snakes going into this. I didn't fear them, I didn't love them. After awhile spending time in the snake dens, you learn to appreciate their finer points and see the world from their point of view. They do these cute [behaviors called] periscoping, where they stick their necks up and look around.

They'll come and investigate you. In the den, they're not [behaving normally], since they're so focused on mating. If you're not a female snake, you might as well be a rock. The instant you sit down, you're literally covered with them.

Tourists view the dens by walking on a boardwalk. Snakes are all over the place. Interpreters are on hand and encourage people to pick one snake up at a time. There aren't many places where you can go and interact with wild animals like that. They're totally harmless, but they do have a line of defense if they get startled—emitting a bodily fluid on you. It's not feces, but it smells just as bad.

Any interesting or unusual things happen to you during your filming?

This was completely different than other wildlife stories I've shot. Most of the time the challenge is locating and getting close to the wildlife—here the challenge was to not step on them or take them home in your camera bag. They coil up everywhere.

Is this annual gathering threatened in any way?

Manitoba has had severe, early winters [including one in 1999], during which a lot of snakes didn't make it back to the dens in time, and there were massive die-offs. It's stable now. The other issue is [snakes crossing the nearby] highway. Local legend has it that cars were skidding off the road because [the roads] were so oily due to dead snakes. Previously, about 20,000 snakes were dying on the highway each year. Ironically, the very people who were coming to see the snakes ended up running them over. But a great grassroots effort reduced the highway mortality to 2,000 by installing pipes underneath the highway, allowing the snakes to pass safely.

Are there other places that this happens?

Nowhere do they congregate in such great numbers. There's a lot of really amazing science going on there, including a team of researchers in Oregon led by Dr. Bob Mason, who has been going up there for over 30 years.

What's interested you the most about the snake pits?

Mating balls are the most intriguing part. All of the males come out first and hang out at the base of the pit, and females are instantly mobbed. The females then give birth out in the summer grounds, in the marshes. The curious thing is that those newborns are immediately abandoned. None of those newborns return to the dens. They find spots in the summer grounds to overwinter. Not much is known about why they don't migrate to the dens or how they survive the winter. (See more of National Geographic's snake videos.)

Another mystery is the snakes' loyalty to their dens: They return to the same den each year. How do they make it back? Some suspect they follow pheromones of other snakes. The obvious question is, how does the first snake find its way back?

What do you want readers to take away from your visit to Narcisse?

You always hear people say, "I hate snakes," but they're incredible species. One insightful little boy [told me], people are afraid of snakes because the way they move is mysterious and [unpredictable]—it's almost like they're under a spell. (Related: "Fear of Snakes, Spiders Rooted in Evolution, Study Finds.")

Getting down on your belly and actually spending time with a calm, [nonpoisonous] snake gives you an appreciation for them, and that fear will disappear.

This interview has been edited and condensed.