There’s Just One True Water Snake in Wisconsin

At least 21 species of snakes call Wisconsin home. Wisconsin’s geography varies widely and includes many different bodies of water, including Lake Superior to the north and Lake Michigan to the east. All of this water combined with its forests and abundance of wildlife, makes Wisconsin a great home for snakes. In this article we’ll look at the one and only true water snake in Wisconsin.

All snakes are adept swimmers and there are several other types of semi-aquatic snakes that are often seen in or near water, but they aren’t actually water snakes.

Water snakes in Wisconsin – meet the northern water snake

The only species of snake from the Genus Nerodia that you’ll find in Wisconsin is the common water snake, more specifically the subspecies referred to as the northern water snake.

We will use these names interchangeably throughout this article, as they are the same species. They, along with the garter snake, are among Wisconsin’s most common snakes and are actually very populous in the area.

Northern water snake

northern water snake | credit: Shenandoah National Park

Scientific name: Nerodia sipedon sipedon
Adult size: 4-5 feet

The northern water snake is actually a subspecies of the common water snakes and comes in a variation of colors, including gray, tan, brown and buff. Juveniles are usually more brightly colored than adults. Adults have dark dorsal bands along their back that are present on the anterior portion of the body. The further down their body you go, the colors change to alternating dorsal and lateral blotches. Their ventral scales, which are on their underbelly, have dark, crescent-moon shaped markings. This is just a guideline for this snake, many other types of water snakes can look very similar!

Northern water snakes range in size from 24 to 55 inches, approximately two feet to four and a half feet. As mentioned, they are fairly dark-colored. Adult females are larger than males most often. Females are live-bearers and breed April through June. Live-bearing means they do not lay eggs, they produce live snakes, often around 12-36 babies, in the late August to early October time frame.

They are found most anywhere there is water. Specifically, they are easily found throughout the eastern half of the United States, especially in the Northeast and Midwest. They are not endangered and are actually quite a heavily populated snack in their native areas.

Habitats and diet

Northern water snakes are not picky and like a wide variety of aquatic habitats. They do prefer slow-moving or standing water, such as ponds, lakes, and marshes, but can also be found on rivers and basically any wetland area.

These snakes spend their time swimming below the water or basking on rocks in the sun. They prefer areas more directly exposed to the sun, so shady areas should be relatively clear of this snake. The northern water snake can also be found hanging out in trees and laying out on branches.

For their diet, these snakes primarily eat fish and amphibians, swallowing them alive. They commonly eat sunfish, smallmouth bass, minnows, toads, frogs, bullfrog tadpoles, trout, catfish, etc. But they’re not picky eaters, they will eat most any animal they find. This actually makes them quite a beneficial species to have around, as they will clear out pests such as mice and rodents.

Demeanor

While the northern water snake isn’t venomous, they are still a wild snake and are not exactly friendly. In fact, they are quite the opposite. The common water snake is known to be fairly aggressive and will bite when handled. This bite will not cause any major harm, as they are non-venomous, but most people will still want to avoid a nasty snake bite.

The common water snake’s main defense when feeling threatened is their production of a musky secretion from the glands near their tail. They may also defecate or vomit. It’s best to always leave any snake in their natural habitat alone to avoid an unfortunate encounter.

Northern water snakes are mostly solitary animals and are primary diurnal, meaning they are most active during the day, though they will hunt at night. They hibernate in the winter and are most social immediately before and after hibernation. Quarantine vibes, anyone? During this time, you may see groups of common water snakes basking together on rocks and enjoying the sun.


Venomous Snakes in Wisconsin

Like all true water snakes, common water snakes are non-venomous. They can become quite aggressive when be disturbed or hassled, but will cannot cause much harm to humans. Their coloring is similar to a few venomous snakes like the water moccasin or cottonmouth, but this species does not occur in Wisconsin.

There are only 2 venomous snakes in the state of Wisconsin, the timber rattlesnake and the massasauga rattlesnake. Neither of these look like water snakes, but common water snakes are mistaken for venomous snake frequently nonetheless.

Simply look for bands around the snake’s body. This means it is a common water snake. If you see blotches and a stripe down the back, it is more likely a timber rattlesnake, but encounters with these snakes are very rare.

timber rattler | source: USFWS Midwest Region

The most common snake the northern water snake is confused for is the cottonmouth. This species is a large, venomous snake that isn’t even found in Wisconsin as we mentioned, but is common in many other areas. The two do look quite similar, so it’s easy to see where the confusion comes from and how concern could be raised when you encounter an unknown species.

How can you tell if it’s a water snake?

There is no foolproof way to distinguish between the two without getting too close, which we don’t recommend. But if you see a snake and are unsure if it is a common water snake or a cottonmouth, look at their head. Venomous snakes have a triangular, boxy shaped head that is wide at the base, where their venom is stored. Water snakes have slender heads that are more flattened. You can even look at their whole body. Cottonmouths tend to be very large and thick, while northern water snakes are smaller and thinner.

Two other ways to tell is that non-venomous water snakes have round pupils, not cat eyes, while venomous species do. Finally, northern water snakes have no heat sensing PIT organ on either of their head between the eye and nostril, while a venomous cottonmouth will. This will basically look like an extra set of nostrils, which will help you tell the snake is poisonous. 

If those don’t help, this trick might. Common water snakes prefer to swim underwater with just their head poking out. Cottonmouths, and most venomous snakes, mostly swim on top of the water.

About Jesse

My name is Jesse. I've always been interested in reptiles and have owned many different types in my life. On this blog I share some of the things I've learned over the years and am still learning about reptiles.