Wildlife Informer is reader-supported. When you click and buy we may earn an affiliate commission at no cost to you. Learn more.

3 Species of Invasive Water Snakes in California 

Not only is California bordered by the Pacific Ocean, but many bodies of water are found throughout the state, ranging from lakes and bays to ponds. It’s not unusual to spot native aquatic snakes, like garter snakes, in these waters. In recent years, it’s become increasingly common to see water snakes that aren’t native to California.

There are no native water snakes in California, but the pet trade has brought several invasive species to the state. Currently, there are three types of water snakes with confirmed populations in The Golden State. Read on to learn more about these aquatic snakes and where they can be found.

Collage of water snakes in California
Collage of water snakes in California

3 Water Snakes In California

While a variety of aquatic snakes are found across the U.S., only a few are considered true water snakes. These snakes primarily live in bodies of freshwater. Since the water snakes found in California are invasive, they threaten other aquatic creatures in the region.

Currently, three invasive water snake species are confirmed to live in California: the Northern water snake, the Southern water snake, and the diamond-backed water snake. Other native aquatic snakes, like the Sierra garter snake and the California red-sided garter snake, can also be found in the state.

1. Northern Water Snake

Northern water snake basking
Northern water snake basking | image by via Flickr | CC BY 2.0
  • Scientific nameNerodia sipedon
  • Length:  24” to 55”
  • Venomous: No

These snakes are typically found in shallow freshwater habitats, including lakes, rivers, and ponds. Most snakes are tan or brown, with white or yellow-colored bellies. Although these snakes aren’t venomous, their bites are painful, and they can release a strong-smelling substance when threatened. It eats a varied diet that includes frogs, fish, and small mammals.

Although the northern water snake is not native to California, two confirmed populations exist in Roseville, CA. These snakes are most likely seen in Kaseberg Creek, a freshwater creek in the Sacramento area. Experts believe that the population could spread to other parts of the state, like central California.

2. Banded Water Snake

Banded water snake resting
Banded water snake resting
  • Scientific name: Nerodia fasciata
  • Length: 22″ to 42″
  • Venomous: No

A subspecies of the southern water snake, these stout snakes are dark in color, with crossband-like markings throughout their bodies. While it can be spotted in various freshwater habitats, it prefers smaller water bodies, like ponds and marshes. It mainly feeds on small aquatic animals, like frogs and salamanders, and is known to swallow its prey whole.

The banded water snake is native to the southeastern U.S. but has been introduced in multiple locations in California. Currently, there are confirmed populations in a reservoir near Lake Natoma, located in Folsom, CA, and the Sacramento River. There have also been sightings in Los Angeles County. Since many amphibian species in California are under threat, this snake poses a risk to native animals in the state.

3. Diamond-backed Water snake

Diamondback Water Snake
Diamondback Water Snake | k.draper | Flickr | CC BY-ND 2.0
  • Scientific name: Nerodia rhombifer
  • Length: 30″ to 48″
  • Venomous: No

True to its name, the diamond-backed water snake has dark, diamond-shaped markings across its body. Most snakes are green or brown in color, with light yellow bellies. Even though these snakes aren’t venomous, they’re highly aggressive and are known to bite humans. They’re diurnal hunters that prey on many aquatic species, including fish, frogs, and salamanders.

You may also like:  8 Species of Hawks in New Hampshire (With Pictures)

These snakes are native to the Central U.S. but have also been introduced to California. A confirmed population can be found in the Lafayette Reservoir, which is located in Contra Costa County. Animal control has worked to remove these snakes, so it’s far less common than other invasive water snakes found in this region.

FAQs about Water Snakes In California

Are There Other Aquatic Snakes In the State?

There are only three types of water snakes in California, but many other aquatic snakes can be found throughout the state. Common aquatic or semi-aquatic snakes include the Santa Cruz garter snake, San Francisco garter snake, two-striped garter snake, checkered garter snake, giant garter snake, and the valley garter snake.

What’s the Difference Between Garter Snakes and True Water Snakes?

The water snake species found in California have diamond or crossband-like markings. In contrast, most garter snakes have a stripe that runs along the center of their backs. Many garter snakes are also smaller than true water snakes, but size can vary from species to species.

Are Garter Snakes Venomous?

Many garter snakes are non-venomous, and the venomous species produce a weak venom that’s not dangerous to humans. While most species in California aren’t considered aggressive,  these snakes may bite people when threatened. It’s best to avoid handling wild snakes when possible.

Is It Legal to Bring Water Snakes to California?

Water snakes are classified as a restricted species, which means these snakes cannot be transported to California without a permit. If you spot a water snake in the state, contact the California Department of Fish and Game for assistance. Snakes in captivity should not be released into the wild.