Invasive, Non-native Snakes Showing Up Across California

Researchers at UC Davis say two non-native water snakes may threaten fragile aquatic species in California.

Their study shows that about 300 individuals of the Common Watersnake and the Southern Watersnake have been found in the Sacramento area and in Long Beach. The snakes are common to waterways in the eastern United States but they are not native to California.

Study co-author Brian Todd said the non-venomous snakes could feed on native fish, amphibians and reptiles - and compete for food with two threatened California gartersnakes (the Giant Gartersnake and the San Francisco Gartersnake).

Todd suspects the invasive species were most likely introduced by people releasing pet snakes they no longer wanted.

The study is intended to give state wildlife managers a jump on eradicating the two invasive water snakes before they spread and do harm, said Todd.

“So what we did was try to get out on front of an issue and get some idea of the risk posed by these non-native species to other native species in California with the hope that that could guide management for the removal or eradication of these non-native species,” said Todd, an Assistant Professor with the UC Davis Department of Wildlife, Fish and Conservation Biology.  

Todd said he has been in touch with state officials about the invasive snakes. He said if action is not taken now, it will cost more ecologically and economically to control the snakes once they're more established.

He said the Common Watersnake has the potential to spread through Central California and north to Oregon and Washington.