New DNA evidence suggests that California's nutria problem didn't begin with a few individuals that quietly survived the state's extermination campaign. Instead, humans may have illegally introduced these nuisance rodents decades later.<\/p>\n
The rediscovery of nutria in California's San Joaquin Valley in 2017 left conservationists asking a key question: Where did these large, semi-aquatic rodents come from?<\/p>\n
According to Smithsonian Magazine, the state Department of Fish and Wildlife stated that genetic studies linked nutria in California to a population in Central Oregon, suggesting that humans were intentionally moving the animals across state lines. The department announced this discovery in April.<\/p>\n
As reported by Smithsonian Magazine, researchers compared the DNA of modern nutrias with skin and skull samples dating back several decades, housed in California museum and university collections. Their study, published in November in the journal Evolutionary Applications, found that older California nutrias descended from multiple lineages, while the current population descends from a single lineage.<\/p>\n
According to Smithsonian Magazine, the discovery indicates a recent repopulation, rather than a hidden population that persisted after California declared it extirpated in the late 1970s.<\/p>\n
Nutria can grow to about 75 centimeters in length and weigh more than 9 kilograms, and they are capable of causing damage to wetlands, crops, dams, and other water infrastructure.<\/p>\n
California spends about $5 million annually to eradicate this pest, and the effort covers several hundred thousand acres of wetlands and riparian habitats in the Sacramento-San Joaquin River Delta and Central Valley.<\/p>\n
These rodents pose a threat to dams and earthen levees, which are already under strain from atmospheric rivers, drought, and groundwater pumping. "Coypu can weaken dams to the point where even minor stresses or environmental changes can trigger their failure," engineering professor Farshid Vahedifard told New Scientist in 2023, as reported by Smithsonian Magazine.<\/p>\n
After a pregnant nutria was discovered in Merced County in 2017, a massive cull campaign was launched in California. Since then, 7,841 nutria have been captured.<\/p>\n
Wildlife conservationists use visual surveys, motion-activated cameras, traps, and scat-sniffing dogs to track rodents. Researchers have created a global nutria DNA database that could help other organizations more quickly identify and monitor rodent infestations.<\/p>\n
Nutria have thin, rat-like tails, orange front teeth, white whiskers on their faces, and dark ears edged with light fur. However, they are easily confused with muskrats, beavers, river otters, and minks, and most reports of nutria to state wildlife agencies turn out to be muskrat sightings, reports Smithsonian Magazine.<\/p>\n
State law says nutria can be killed "by any lawful means" if they cause damage to property or crops, and citizens are required to report the killing to state authorities, ideally with photos and the carcass.<\/p>\n
\u00ab"Given the location of the nutria rediscovery in California, it's virtually impossible that they migrated there on their own," Michael Buchalski, head of wildlife genetics at the California Department of Fish and Wildlife, told SFGate in April, as reported by Smithsonian Magazine. "...This makes human intrusion the most likely scenario.".<\/p>\n
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