The record
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- California had eradicated invasive nutria by the late 1970s, but the rodents reappeared in the Central Valley starting in 2017.
- A new genetic study by the California Department of Fish and Wildlife found today's nutria are most closely related to a population in central Oregon, not the state's historic animals, indicating humans likely reintroduced them.
- This matters because nutria damage wetlands, levees, and crops, and the state is spending about $5 million a year to remove over 7,800 animals since 2017.
- The finding suggests preventing future invasions requires biosecurity and transport controls, not just trapping.
What to watch next
- Whether officials can identify the source or person behind the reintroduction
- Updates on the $5 million-a-year eradication effort in the Sacramento-San Joaquin Delta and Central Valley
- Use of the new genetic reference dataset to trace invasion pathways and tighten transport rules
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Named United States · California · Central Valley · Merced County · Sacramento-San Joaquin Delta · California Department of Fish and Wildlife · Oregon · US Department of Agriculture
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