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Are There Water Snakes in South Dakota?

Nestled in the heart of America’s Great Plains, South Dakota is a land of rugged beauty, with its rolling hills, towering rock formations, and crystal-clear lakes. But did you know that this large state is also home to one of the only water snakes species found in the region? That’s right – the Northern Water Snake is actually an interesting snake species that thrives in the rivers, lakes, and wetlands of South Dakota.

This article will take a closer look at this elusive species and uncover the mysteries of its existence in this unique part of the country. So, get ready to explore the world of water snakes in South Dakota:

There’s One Type of Water Snake in South Dakota

There is only one species of true water snake found in the state: the Northern Water Snake (Nerodia sipedon). While there are other semi-aquatic snakes in the region, such as garter snakes and ribbon snakes, we will only focus on this species for this article.

Northern Water Snake

Northern water snake basking
Northern water snake basking | image by via Flickr | CC BY 2.0

Scientific name: Nerodia s. sipedon

The Northern Water Snake, also known as the common water snake, is a large-bodied, non-venomous aquatic snake native to North America. These snakes are often mistaken for the extremely venomous copperhead or cottonmouth. They can be easily identified by their lack of a triangular head shape and other identifying characteristics.

The Northern Water Snake has a gray, reddish, brownish-black, or brown body with dark-colored crossbands on its neck. It also has beautiful dark blotches on the rest of its body, which is why most inexperienced people misidentify it as a copperhead or a cottonmouth

As the snakes of this species age, the blotches on their bodies become more obscure, and their primary body colors darken. They also have a different color on their bellies- with some individuals having gray, white, or yellow underbellies with black or reddish-brown crescent shapes.


Northern Water Snake
Northern Water Snake | Shenandoah National Park

The common water snake can grow to a total length of about 4.5 feet. Females tend to be larger and weigh more than males, with average lengths of 2 ft 8 in. and 3.5 ft, respectively.

When it comes to weight, females typically weigh between 5.5 to 14.5 oz, whereas males are much smaller at 2.8 to 5.3 oz. However, the largest males can weigh up to 13 oz, while the largest females can reach up to 20 oz.

The main reason why females are larger than males in this species is that there is no male-male competition, and female size increases in order to increase fecundity- the ability to produce offspring.

Habitat and Geographic Range

The Northern Water Snake is a semi-aquatic species and prefers slow-moving rivers and streams or stagnant ponds, lakes, and marshes with abundant fish populations. They can often be seen sunning themselves on rocks, logs, or anything else that is sticking out of the water.

But while these snakes are almost non-existent in South Dakota, scientists have spotted them in a tiny area in the southeastern part of the state near the Missouri River as well as some of its tributaries.

Behavior and Diet

Northern Water Snake | Andrew Hazen

Northern Water Snakes are active both during the day and at night but prefer to be around water. These reptiles are semi-aquatic ambush predators, meaning they wait in hiding while their prey passes by, and then they strike, often swallowing their prey alive.

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During the day, these reptiles often hang around the plants near the water’s edge, hunting for prey. Their diets consist of small fish and amphibians, such as frogs, tadpoles, and salamanders, other small snakes, small birds, large insects, crayfish worms, and leeches.

At night, these snakes focus on hunting small fish, such as minnows found resting in shallow waters. One of the most impressive things about the Northern Water Snake is that it hunts using a sense of smell and sight, which makes it very effective in finding its prey even at night.

Protection against predators

The Northern Water Snake has a lot of predators, including snapping turtles, raccoons, birds, foxes, opossums, other bigger snakes, and even humans. But when it feels threatened by a predator or someone picking it up, the common water snake will aggressively bite multiple times and excrete a foul-smelling musk to protect itself.

It also contains mild anticoagulants (or blood thinners), which cause the bite wounds to bleed more because it stops the blood from clotting. However, this snake causes little to no harm to humans and is non-venomous.

Mating and Reproduction

Northern water snakes basking
Northern water snakes basking | image by Judy Gallagher via Flickr | CC BY 2.0

Nerodia sipedon mates around April, May, and June and reproduces using an ovoviviparous reproductive strategy. This means that instead of laying eggs like many other snakes do, the female carries her eggs inside her body until they are ready to hatch and gives birth to live young.

The young are usually about 7.5 to 9 inches long when born and arrive between August and October. The females in this species often give birth to up to 30 live young ones with the average being eight. Mothers don’t nurse or care for their young, but multiple mating by the females is common and leads to a focus on sperm competition.

Interestingly, multiple mating by females is common in this species, leading to an emphasis on sperm competition among males which may explain why the success of a male does not necessarily depend on its size but rather on the quality of its sperm.


While this species isn’t endangered, it’s at risk of habitat loss due to human competition. Additionally, these snakes are often killed by humans, making them vulnerable to population declines.

To help protect this species, it’s important to reduce habitat fragmentation and destruction, support conservation efforts that focus on maintaining water quality, and educate people about this species so they can learn to appreciate them instead of killing them.

How to Distinguish Between the Northern Watersnake and the Venomous Cottonmouth

Because of the misidentification of the Northern Watersnake, most of them are often killed by humans out of fear. So, it’s important to know how to distinguish between the two species.

The common watersnake is longer and more slender than the Cottonmouth, with a flattened head that’s as wide as its neck. It also has round pupils, with no pit organs for sensing heat between its nostrils and eyes.

On the other hand, the cottonmouth boasts an impressively plump physique. It also has a bigger body than the northern watersnake and a triangular skull that displays venom glands wider than its neck. Its eyes have unmistakable cat-like pupils, with heat-sensitive pit glands (or depressions) that lie between its eyes and nostrils.

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These pit organs contain a membrane that helps cottonmouths detect warmth through infrared radiation from other animals’ bodies. These glands can detect warm bodies up to three feet away.

Fun Fact About South Dakota Water Snakes

These snakes are quite social during the cooler months, especially in spring and fall. Researchers have observed them coiled together (almost like cuddling) while basking in the sun to help conserve energy.

They may even be seen basking in tight clusters containing up to twenty individuals! This behavior is thought to help regulate the body temperatures of these snakes, ensuring they stay warm enough during colder periods of the year.

However, when the warmer months approach, the N. sipedon changes into a solitary creature often seen on cattail stems, walkways, and overhanging tree branches.