Invasive Water Snakes Heading For Oregon?

California’s budding population of invasive common watersnake could make it up to Oregon due to similar climate and suitable habitat in the Willamette Valley, according to a recent study at University of California, Davis, that projected possible areas of infestation.

Although the original source of the water snakes is uncertain, they were not introduced through natural means such as natural disaster or climate change, according to Brian Todd of the UC Davis Department of Wildlife, Fish and Conservation and co-author of the study. “The three populations of water snakes in California were established before 2008, so there is the possibility that they were pets that were unwanted, or were intentionally released,” Todd says. “But it’s not a natural occurrence — they were definitely brought here by people.”

The common watersnakes are nonvenomous, though Todd notes that they have a “nasty temperament” and may leave an unremarkable bite. The biggest concern is the impact the snakes will have on native populations of amphibians and fish, as California has already begun to see them interrupt native habitats and eat native species.

Rick Boatner, invasive species and wildlife integrity coordinator of Oregon’s Wildlife Division, says that the red-legged frog, yellow-legged frog and Pacific tree frog are just a few species that might be negatively impacted by the arrival of the common watersnake. “Currently that family is uncontrolled in Oregon, which means that anyone can have it for a pet without permits or anything,” Boatner says. “We’ll be doing a risk assessment to see if we need to move it to a prohibited species.”

Most of the common watersnake’s arrival in Oregon depends on how California deals with its population. “It’s a relatively new problem and both the state and federal authorities are spread pretty thin, dealing with a lot of problems that are already more widespread. This one is still in its early stages,” Todd says. Without any transportation help from people, Todd estimates that it would take 20-50 years for it to spread naturally up to Oregon. However, there is still potential for Oregon to create its own accidental invasive population.

“People should never release unwanted pets. Even if it’s a native species that you have legally, you should not release it because it could have a disease that could spread to native populations,” Todd says. “Or if it is non-native, it could potentially become an established invasive pest.”

Oregon does have the Pacific Coast aquatic garter snake, which is native and can be found in streams and ponds.

To report sightings of the common or Southwestern invasive watersnake or other invasive species, contact Oregon Department of Fish and Wildlife’s Rick Boatner at