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6 Types of Water Snakes in Illinois (Pictures)

True water snakes are a group of non-venomous, aquatic snakes that are adapted to living in or near bodies of water. While there are several species of snake that spend time in the water, true water snakes of members of the genus Nerodia. True water snakes are excellent swimmers, and when they are not swimming, they are often found basking on rocks or trees in or near the water. The state of Illinois has several species of water snakes, and this article will discuss the characteristics and habits of these fascinating creatures.

True water snakes have flattened, triangular-shaped heads and muscular bodies that help them easily move through the water. They are often mistaken for other types of snakes but can be identified by their specific physical characteristics, such as keeled scales, vertical pupils, and a lack of a rattle or other venomous adaptations.

Photo collage water snakes in illinois

6 Water Snakes in Illinois

Illinois is home to six species of water snake, including the common water snake, the green water snake, the diamondback water snake, the yellowbelly water snake, the copperbelly water snake, and the banded water snake. 

1. Common Water snake

common water snake hissing
Common water snake hissing | image by icelandgull via iNaturalist | CC BY 4.0

Scientific Name: Nerodia sipedon

The common water snake, also known as the Northern water snake, is the most common water snake species found in Illinois. It is the only water snake that can be found throughout the entire state. They are non-venomous and are typically found in or near water sources such as rivers, lakes, and ponds.

Northern water snakes are dark brown or gray in color with dark blotches along their body. This species is often mistaken for venomous water moccasins, which are not true water snakes.

Common water snakes have vertical pupils in their eyes and keeled scales along their bodies, meaning the scales have raised ridges that give them a rough or bumpy texture. They feed primarily on fish but will also eat amphibians, small mammals, and other snakes.

2. Green Water snake

Green water snake
Green water snake | image by Glenn Bartolotti via Wikimedia Commons | CC BY-SA 4.0

Scientific Name: Nerodia cyclopion

The green water snake can be found in streams, rivers, and marshes in Southern Illinois. This species has a light green or olive-colored body with darker green or brownish blotches along its back. Like other water snakes, the green water snake has keeled scales, vertical pupils, and a flattened head that is wider than its neck.

These excellent swimmers mainly eat fish but will sometimes snack on frogs and other small aquatic animals. Though some may think these snakes look intimidating, they are not typically aggressive and will often retreat when disturbed by humans.

3. Diamondback Water snake

Diamondback Water Snake
Diamondback Water Snake | k.draper | Flickr | CC BY-ND 2.0

Scientific Name: Nerodia rhombifer

This water snake species can be found in rivers, lakes, and ponds in Illinois’s southern and eastern parts. The diamondback water snake is named for the distinctive diamond pattern on its back.

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A pattern of alternating light and dark brown bands forms a series of diamond shapes. The diamondback water snake has keeled scales and vertical pupils. While their diet consists of mostly fish, they have been known to eat frogs, crayfish, and other aquatic animals.

Diamondback water snakes are known for their defensive behavior, which includes hissing, vibrating their tail, and striking when they feel threatened. Despite this behavior, they are not normally aggressive toward humans unless provoked and will often flee if they are able. This fascinating member of the water snake family is an important part of Illinois’ aquatic ecosystem.

4. Yellowbelly Water snake

Yellowbelly water snake resting
Yellowbelly water snake resting | image by Peter Paplanus via Flickr | CC BY 2.0

Scientific Name: Nerodia erythrogaster flavigaster

The yellowbelly water snake lives in lakes, ponds, and rivers in southern Illinois. As the name suggests, this species has a dark brown or grayish body with a yellow or orange belly.

Like their water snake cousins, they have keeled scales, giving them a rough appearance. They also have the signature vertical pupils and wide, flattened heads that other water snake species have.

The yellowbelly water snake’s diet consists of fish, frogs, crayfish, tadpoles, and other aquatic life. Like the diamondback water snake, the yellowbelly water snake can be quite defensive when it feels threatened. While not venomous, they will strike or bite if they feel threatened.

5. Copperbelly Water snake

Copperbelly water snake
Copperbelly water snake | image by Peter Paplanus via Flickr | CC BY 2.0

Scientific Name: Nerodia erythrogaster neglecta

The copperbelly water snake is similar in size and appearance to the yellowbelly water snake, but as the name suggests, its belly is more reddish-orange in color. This species prefers the swamps, bogs, and marshes of Illinois and can mostly be found in the southern part of the state.

While the copperbelly water snake is not venomous, it can release a foul-smelling musk from a scent gland at the base of its tail when threatened. Unfortunately, this species of water snake is listed as a threatened species in Illinois, and efforts are underway to help conserve and protect its wetland habitat.

6. Banded Water snake

Banded water snake resting
Banded water snake resting

Scientific Name: Nerodia fasciata

The banded water snake can be found in Illinois’s rivers, ponds, and wetlands. This species is gray or brown in color with dark brown or black bands that run the length of its body, which is where it gets its name. These water snakes can grow up to four feet in length and their diet consists mainly of fish and amphibians.

The banded water snake is often mistaken for the venomous cottonmouth, a snake that is not considered a true water snake but does spend much of its time in the water. Despite this common misconception, the banded water snake is completely harmless to humans.

That doesn’t mean they won’t bite if provoked, but they tend to retreat when confronted by humans. The banded water snake is the least common type of water snake found in Illinois but can be seen in the central and southern parts of the state.

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