The Most Snake-Infested Lakes In Montana

A common garter snake slithering in grass

Written by Thomas Godwin

Updated: August 26, 2023

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Snakes are not all that prevalent in Montana, at least not in comparison to some southeastern states, like Florida, Alabama, Louisiana, and Mississippi. In fact, there are only 10 species of snake in Montana. While Montana is certainly not an arid state, it has a much drier climate than most people think.

While none of these lakes are infested, there are quite a few species that can be found at these locations.

There are fewer lakes in Montana comparatively. For instance, Montana has a shade of over 3,000 lakes. That sounds quite impressive until you compare it to Alaska’s 3,000,000, Kansas’ 120,000, or Florida’s 30,000. With fewer lakes and a minuscule number of semi-aquatic states in the state, there’s no reputation for snake-infested lakes in Montana.

Snakes Found In Montana Lakes

Thamnophis brachystoma, the shorthead garter snake or short-headed gartersnake

©Eric Dale/

That doesn’t mean that Montana has no snakes in the lakes throughout the state, just that they aren’t what we would accurately call an “infestation.” There are only three species of semi-aquatic snakes in the state—the common garter snake, the plains garter snake, and the western terrestrial garter state.

Other snakes may hang out close to areas with water, but they prefer the more arid and dry environments across Montana. All snakes can swim, and sometimes, non-aquatic snakes are numerous in and around the lakes in Montana.

In August of 2007, Duane Hons was fishing in the Nelson Reservoir when he came across a prairie rattlesnake, swimming across the lake from one end to the other. Another Angler, Bernie Hildebrand, had a rattlesnake crawl into the boat with him and his fishing partner. The prairie rattlesnake in question was swimming around in Hell Creek Bay.

Snakes in Montana are not unheard of. However, most Montana lakes maintain low populations of specific snakes in the water at any given time.

1. Nelson Reservoir

Nelson Reservoir

Prairie rattlesnake

©Harris Motion Photo/

Besides the above story of Hons and the prairie rattlesnake, Nelson Reservoir is home to a couple of garter snake species, namely the common and western terrestrial garter snakes. Though these snakes are prevalent in the area, they are not venomous and will happily move away from people.

However, Nelson Reservoir is also a huge recreational reservoir where people come to swim, kayak, boat, and fish throughout the summer months for anglers, including the springtime and the fall.

2. Mystic Lake

Mystic Lake

The Plains garter snake can be found at Mystic Lake, along with the western terrestrial.

©Joe Farah/

Getting out to Mystic Lake is a fun hike through some of the most beautiful territory in the entire state. It’s listed as an “easy-level” hike, but that’s more a matter of personal perspective. While you won’t find a snake-infested lake in Montana, there is a chance you might run into a plains garter snake, a common, or a western terrestrial.

It would be rare to run into a prairie rattlesnake at Mystic Lake, given the rocky environment and the snake’s predilection towards plains-like environments (given its name) and more of an arid air.

3. Whitefish Lake

Whitefish Lake

One of the snakes around this large ecosystem is the black racer.


Whitefish Lake is a small part of a much larger ecosystem, incredible in its beauty and natural wonder that includes Bob Marshall Wilderness, Scapegoat & Great Bear Wilderness, National Bison Range, the lake itself, and Glacier National Park.

Snakes in and around Whitefish Lake include the black racer, the common garter snake, the prairie rattlesnake, and the western terrestrial garter snake. However, there are far more warnings concerning grizzly bears in the Whitefish Lake area, and visitors should know to bring bear spray just in case.

4. Fort Peck Lake

Fort Peck Lake

Fort Peck has quite a few snakes, one of which is the hog-nosed snake.


There are reports of prairie rattlesnakes throughout the Fort Peck area, which includes the lake and the aforementioned Hell Creek Bay. Fort Peck is on the eastern side of the state, which means all three of the garter snakes common in Montana, the prairie rattlesnake, hog-nosed snakes, milk snakes, black racer, and the northern rubber boa are prevalent.

Most snakes in and around lakes in Montana are more than capable of swimming, though spotting them actively in the water is not very common.

5. Flathead Lake

Flathead Lake

The rubber boa is one of the many snakes endemic to Montana and called Flathead Lake home.

©Matt Jeppson/

Five of the ten snake species in Montana call the Flathead Lake area their home. Flathead Lake is the largest natural lake west of Mississippi, covering 200 miles² of territory. It’s a recreational hotspot, so snake sightings occur from time to time throughout the surrounding area.

The five species include the common garter snake, the western terrestrial garter snake, the prairie rattlesnake, the gopher snake, and the northern rubber boa.

Summary Of The Most Snake-Infested Lakes In Montana

RankLakeSnakes Found
1Nelson ReservoirPrairie rattlesnake, common garter snake, western terrestrial garter snake
2Mystic LakePlains garter snake, common garter snake, western terrestrial garter snake, the prairie rattlesnake
3Whitefish LakeBlack racer, western terrestrial garter snake, prairie rattlesnake, and the common garter snake
4Fort Peck LakePrairie rattlesnake, hog-nosed snake, milk snake, black racer, northern rubber boa, plains garter snake, common garter snake, and western terrestrial garter snake
5Flathead LakeCommon garter snake, northern rubber boa, western terrestrial garter snake, prairie rattlesnake, and the gopher snake
Summary Table Of The Most Snake-Infested Lakes In Montana

Other Animals Found Near Lakes in Montana

Summary of the Most Snake-Infested Lakes in Montana

©Scott E Read/

Montana has a wide range of wildlife, and most species are prevalent across the entire state rather than a single type of terrain or location. Grizzly bears are probably the most notorious because encounters with them are often heavily documented. Though you may run into a grizzly in the southern portion of Montana, it’s far more likely in the north and to the west.

In fact, the grizzly bear is Montana’s official state animal. Moose are prevalent across the state as well, and that makes two rather massive animals that live throughout the state. There are more, however, including addax, bison, and rather sizeable mountain goats.

As far as smaller wildlife, they are well represented in Montana as well, such as scorpions, the black-footed ferret, the American pika, and the striped skunk. The most numerous animal groups are in the mid-size range, including wolverines, wolves, bobcats, whooping cranes, the Canada lynx, and the bald eagle.

All Things Considered

Montana is not a state known for its snake populations, with only ten species currently known. When it comes to Montana lakes, you’re as likely to find a snake there as anyone else in a northern state near a body of water.

Fortunately, only the prairie rattlesnake is venomous, and if you are ever bitten by one, you should seek medical attention as quickly as possible. For those with a phobia of snakes, there’s probably no better place outside of Antarctica to enjoy the beauty of nature and wildlife without worrying about too many snakes.

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About the Author

Thomas is a freelance writer with an affinity for the great outdoors and Doberman Pinschers. When he's not sitting behind the computer, pounding out stories on black bears and reindeer, he's spending time with his family, two Dobermans (Ares and Athena), and a Ragdoll cat named Heimdal. He also tends his Appleyard Ducks and a variety of overly curious and occasionally vexatious chickens.

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