Scientists are capturing some of the biggest snakes in Canada, implanting them with radio transmitters, and tracking them to figure out what habitats they prefer and whether they are threatened or endangered.

Bull snakes are non-venomous constrictors — snakes that wrap around their prey and squeeze — that grow up to two metres long.

Their range runs from southern Texas to southern Alberta and Saskatchewan, where scientists at the University of Regina and the Royal Saskatchewan Museum are trying to uncover very basic details about their population and their habits.

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Marla Anderson and Ashley Fortney spend all day every day walking around with a receiver and tracking bull snakes that have already been implanted with radio transmitters. (Bonnie Allen/CBC)

Despite their large size, bull snakes are so reclusive there isn't even enough information for the Committee on the Status of Endangered Wildlife in Canada to determine whether they are risk of extinction and in need of extra protection, said Chris Somers, a University of Regina biologist working on the project.

"You can't just go out and count them," he said. "You can't see them. They hide. They're underground, they're low to the ground. They're well camouflaged."

Because of that, figuring out where the snakes are requires a little help from technology.

Radio transmitters have already been implanted in snakes in three areas of southern Saskatchewan — Big Muddy Valley, Frenchman River Valley and South Saskatchewan River Valley — since 2008. Researchers can find the snakes and follow them by holding an antenna that homes in on the signal of any transmitter-wearing snakes nearby, no matter where they may be hiding.

This year, the tracking program has expanded to the banks of the South Saskatchewan River north of Swift Current, the very northern tip of the snake's range.

Somers's team has already surgically implanted transmitters in eight snakes there and hope to put transmitters in 10 more by the end of the summer.

The goal is to find out where the snakes are, what kind of habitat they use, how much they move and whether they live in families.

Following snakes all day

In order to do that, researchers Marla Anderson and Ashley Fortney follow the snakes with implanted transmitters all day, every day over the rolling grasslands, holding receivers and antennas in front of them to pick up the snakes' signals. Each snake has its own frequency, Fortney said. When the receiver points toward the snake, it emits higher pitched beeps and the signal bars on the screen increase.

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The radio transmitter is surgically implanted in the snake, each with a different frequency. (Courtesy Chris Somers)

Even so, it's not always easy, Fortney said.

"You could be standing two feet from the snake you're tracking and you know it's right there and you can't see it in the tall grass and it doesn't move."

Fortney gave a demonstration, homing in on the signal of a large snake nicknamed Heidi because of an impressive ability to hide despite her large size. On this occasion, Fortney was successful  — after some hunting around, Anderson managed to spot Heidi's coils in a bush, and together the two women managed to grab the snake .

Heidi undulated her body to and fro, trying to escape, but made no attempt to bite.

"They're really quite docile," Fortney said.

Somers said that everything the study has revealed so far about bull snakes is "new to Canada and to us."

One interesting finding has been that each snake's territory includes a winter home consisting of an underground den, a summer breeding site, and a corridor that connects the two, Somers said. In the past, conservation has focused on protecting snakes' wintering grounds.

But Somers said the new research shows that in the case of the bull snake, "that's just one half."

The researchers hope the snakes they are tracking will lead them to different wintering and breeding grounds.

Somers said Saskatchewan is actually one of the "toughest places on the continent" to be an cold-blooded animal like a bull snake that can't regulate its own body temperature. The winters are long and cold, the summers are short and hot, and most of the native grassland has been converted to agricultural land.

"We don't really know how they make a living here, which is amazing to me,"  Somers added. "Because it's the largest snake we have, and yet we don't really know what it does."

With files from Bonnie Allen