Genetic Tests Link Destructive California Nutria to Oregon Population

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Genetic analysis has revealed that the nutria, a large invasive rodent causing problems in California's wetlands and levees, are closely related to a population in central Oregon rather than the nutria that previously lived in the state. This suggests the current California nutria were illegally reintroduced, likely by humans, rather than arriving naturally. Officials have removed over 7,800 nutria since they were first discovered in 2017, and now spend around $5 million per year trying to control the infestation across hundreds of thousands of acres.

Why it matters

The reappearance of nutria in California is a major ecological and economic concern, as the rodents can devastate wetlands, damage infrastructure like levees, and cost millions in control efforts. Understanding how they arrived in the state is crucial to preventing future illegal introductions and managing the existing population.

The details

Genetic testing by the California Department of Fish and Wildlife has shown the nutria found in California since 2017 are closely related to a population in central Oregon, rather than the nutria that were previously eradicated from the state in the 1970s. This suggests the current California nutria were illegally reintroduced, likely by human intervention, rather than arriving naturally. Officials say the animals couldn't have realistically walked the distance between the two areas, and no nutria were found in the intervening regions.

• Nutria were first discovered in Merced County, California in 2017.
• Since then, over 7,800 nutria have been removed from California, at a cost of around $5 million per year.

What’s next

Officials will continue their efforts to remove and control the nutria population in California, while also investigating the source of the illegal reintroduction to prevent future incidents.