Listen: A summer with the NWT’s only snakes

Big Bertha has problems.

Bertha is a red-sided garter snake. The fire scar on her side tells the story of what has been happening to her home just outside Fort Smith, near the NWT-Alberta border.

Fort Smith was evacuated for weeks in the summer of 2023 as multiple wildfires threatened the town. Those fires rolled right over Bertha’s habitat.

These snakes are the only reptiles confirmed to exist in the territory. If those fires killed too many snakes or ruined their habitat, who knows what might happen to those that remain.

That’s where Johanna Stewart comes in.

Stewart, from Yellowknife, is an environmental science master’s student at Thompson Rivers University who is helping to lead a project that spends two years tracking Bertha and friends.

How are the snakes doing? How many are there? What happened to their habitat and how are they responding?

Stewart spent this summer starting to collect the data that might answer those questions. That meant plenty of days out on the land around Fort Smith, following the snakes, tagging them with tiny microchips and studying what was going on.

Cabin Radio checked in with Stewart just as that work was starting in May, about six weeks later at the end of June, and again in the fall once the summer work in the field had finished.

On the Cabin Talks podcast, you can hear those conversations and follow the journey of Stewart – and the snakes – as the work unfolds and we begin to learn more. (Get the show wherever you get your podcasts.)

Below, we’ve transcribed some key excerpts from each conversation. You can also check out photos from the summer’s work.

Year two is expected to reveal more about how the snake population is changing and where, exactly, the snakes go each summer when they leave their dens for the wetlands.

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The following excerpts come from conversations with Cabin Radio’s Ollie Williams over the course of 2024. Transcribed excerpts have been edited for length and clarity.

May: Remarkable creatures

Johanna Stewart: This study came about quickly. After last year’s extreme forest fire season, the GNWT was concerned about the status of snakes in the territory. My understanding is that they reached out to Thompson Rivers University, where my supervisor, Karl Larsen, is a professor.

Karl did the original study, I think the first intensive study of red-sided garter snakes, back in the 1980s. He has a lot of knowledge about snakes in the area. They asked if he would be willing to help with a post-fire study of the snake population, and they brought me on as a grad student to lead that work.

The red-sided garter snake is the only known reptile in the NWT. Here in the North, we are at the very northern extent of where that species can survive. They are impressively adapted to our climate here: they go underground and live in these cracks or crevices, dens in the limestone karst in this region, and they hibernate there.

Their body temperature is maintained quite low throughout the winter and they survive like that for months. Then they emerge in the spring.

This year, they were observed basking on the snow while there was still snow on the ground, which – for any snake – that’s impressive. When the females emerge, the males all attempt to mate. That’s what creates these mating balls that people are usually interested in coming to see. After that, they disperse into the wetlands and they are there for the summer as they hunt for their prey, which is mainly frogs in this region.

They can migrate relatively long distances: they’ve been found several kilometres from their original den. They’re pretty remarkable creatures and yet we don’t know enough about them. They haven’t been super well studied in this region. This study is a great opportunity to learn more about them in general and also specifically to look at what were the impacts of last year’s fire.

I am trained to capture the snakes. We take their length, their weight, their sex, and then insert a small passive integrated transponder. That’s a fancy phrase for a pet tag, a little microchip. If we catch that snake again later, we can scan it with a little device and determine when and where we saw that snake before.

We’re also hoping to implant radio transmitters into snakes that would allow us to track their movements and get a better understanding of where they go in the summer.

We know that a large portion of the snakes’ habitat probably burned in 2023 and was significantly altered by this burn. The fire went right over their winter dens and also through a lot of their summer habitat. That could make it more difficult for them to survive, finding enough food to keep them healthy.

June: ‘It’s really hard to see’

It’s pretty wild to see the conditions the snakes are living in. It’s almost surprising to me that they survived and got back to the dens, some of which are completely scorched.

Walking all over that landscape, there’s very little water. These snakes are going all winter without water and need to find that once they come out of hibernation. They need to make their way to wetlands, some of which are kilometres away, to find prey.

It’s a major obstacle course to make it through that landscape without falling prey to some other animal. So it’s really hard to see all the challenges that they’re facing – and still, it’s encouraging that they at least so far have found a way to survive.

While it’s encouraging that we are seeing snakes at all of the dens we knew about, the numbers are not astronomical. They’re relatively low.

We got a bit of a late start, so it’s possible we missed some snakes emerging during that earlier window. Next spring, once we are recapturing tagged snakes, that will be the point at which we can start making some estimations of the population size.

Late October: Planning some reunions

A big question I have now is: what are the real threats to the snakes?

We did find a number of dead snakes on the landscape, which is really unfortunate, but I think it’s really important to look at that and try to get ideas of what is actually affecting these snakes and causing mortality.

We collected a whole bunch of samples and sent them to the lab for analysis. Is it disease? Is it just body condition? Did these snakes go into their hibernation in a stressed condition, and then were just not able to survive upon emerging from the dens?

There’s always some mortality. One person told me they are used to seeing roadkill of snakes around Fort Smith – and it was actually something notable when they didn’t see the roadkill. That was in 2023 just after the forest fires. They did not see the same level of roadkill and so that, in a way, can actually be an indicator. It was a cause of concern for this person: “I’m not seeing the same number of dead snakes here that I usually do. Does that mean there are fewer snakes out there?”

To some degree, it is normal to be seeing mortality out there. Figuring out whether the level that we are seeing is normal in this post-fire situation, that’s what we’re hoping to clarify if we can.

We went into this summer with the initial question of whether or not there were still snakes present at previously known denning locations at all, given that the fire went right over these sites, and yes – there were still snakes found at all known denning locations. So that was an important finding, even though the actual number of snakes at these dens is still unclear.

I’m in a little bit of that uncomfortable position where it feels like I’ve come out of a field season almost with more questions than answers.

We did get to tag a lot of snakes on the landscape. We tagged more than 200 snakes with transponders. That’s how we identify an individual snake and know we have caught it before. We’ve got some ideas, though no firm conclusions.

Next year, hopefully we’ll be doing snake telemetry – implanting snakes with transmitters and then being able to follow them to their summer habitat. At this point, what habitat they’re using throughout the summer months, once they leave the den and before they return, is still a big unknown.

I’ve also heard from a lot of people giving me ideas of “you should check out this spot” or “you should talk to this person.” There’s a whole lot of follow-up and I’m excited for a full second field season next year.

I would be really excited to see Big Bertha again. She was the very first snake that I tagged this summer. She had a big fire scar on her, making her easily recognizable and also letting us all know that she had been through something and survived. I’m really rooting for her.

Big Bertha is emblematic of what we’re trying to do here, which is understand how snakes were affected by the fire, and also how they are resilient to it. Understanding that for the whole population is the goal, but every snake is a win.

I get excited by every snake that I see, and I will be so excited to see them next summer. The only part of this little fairy tale that is inverse is that the snakes maybe aren’t so excited to see me next summer. If they do remember me at all, it’ll be like, “Man, here comes that researcher again.”

But yeah, the hope is I will be seeing some of my captured snakes again. Those will be my recaptures, and they’ll be really important for getting that population abundance estimate. So here’s hoping for some reunions.