Eradication of invasive nutria off to a slow start in California
Posted May 12, 2018 6:13 p.m. EDT
LOS BANOS, Calif. -- Before the midday heat had set in, Jeff Cann and Tim Kroeker were out of their Dodge pickup, trudging through waist-deep water in waders and rubber boots.
The two wildlife biologists had come to this vast expanse of sun-soaked Central Valley wetlands on a recent morning to check in on the first traps that California has authorized in its nascent effort to hunt -- and exterminate -- the nutria.
The invasive rodent from South America, which can grow to 3 feet long and weigh 25 pounds and breed furiously, has been found burrowing beneath rivers and marshes in six counties. If it continues to spread, state officials fear it will not only ravage crops and wildlife habitat but upend dikes and dams, possibly flooding homes and undermining water supplies at a time whenclimate change is already testing California's water infrastructure.
Officials thought the animal had been wiped out of the state 50 years ago, eliminating the threat of tens of millions of dollars in losses, which other infested parts of the U.S. have seen. But they were wrong.
``You can see the sagging cattails over there,'' said Cann, pointing to a cluster of trampled swamp plants where a trap had been set in the North Grassland Wildlife Area, about two hours southeast of San Francisco. ``That's an area where the nutria have been.''
After splashing through a shallow lake, he and Kroeker arrived at the site Cann had motioned to, but they found no immediate signs of life. Their trap was empty, and the sweet potato the biologists used for bait was gone.
Two months into their eradication campaign, officials at the California Department of Fish and Wildlife acknowledge they face a steep learning curve, as well as a lack of money and manpower, as they fight against an aquatic animal so resilient and so prolific that experts say hundreds of thousands, even millions, could surface within a few years if left unchecked.
Cann and Kroeker are part of the initial response team of six, aided by a handful of federal employees.
``It's going slowly,'' said Terry Palmisano, the state incident commander in charge of the nutria eradication. ``Literally, we're dealing with thousands and thousands of acres to cover and a small number of people in the field.''
Palmisano expects the response crew to get more funding and at least double in size. The team recently won two grants worth a combined $1.8 million. The program has been operating on reassigned staff and a few hundred thousand dollars shifted from other state accounts.
``If this is truly important to the state, I hope that when I turn my back, there's an army there to help us,'' Palmisano said.
To increase the odds of success, the team also must improve its methods of catching the animal. Just 63 nutria have been killed so far. The largest was a pregnant female weighing 24 pounds.
``You learn a little more each time you go out,'' said Kroeker, who, like most of his California colleagues, is more accustomed to corralling deer and elk than swamp rodents.
At present, the team's main focus is on simply figuring out how widespread the nutria have become. The state is still conducting population surveys, though it has confirmed sightings in the counties of Merced, Fresno, San Joaquin, Stanislaus, Tuolumne and Mariposa.
Wildlife officials hope the rodent hasn't established itself to the north in the Sacramento-San Joaquin River Delta. The sprawling wetlands, where California's two largest rivers converge, offers prime nutria habitat. But it's also the hub of the state's waterworks. The fragile system of levees and berms that helps channel water through the area to cities and farms across the state is already bearing the brunt of rising sea levels and worsening flooding, due to global warming.
If nutria take hold in the estuary, not only would the animal have safe, watery passage to many other parts of California, but it could wreak untold havoc on the state's canals and aqueducts, and disrupt water supplies for millions of residents. Compromised dikes could also lead to flooded towns and agricultural lands within the delta.
``This is where we're going to try to put our emphasis,'' Palmisano said.
The first nutria in California in half a century was discovered in March 2017, in a beaver trap at a duck-hunting club in Merced County, not far from where the state has started the eradication effort. The animal was taken to the state's wildlife lab outside Sacramento, where its identification shocked biologists.
``We didn't know what to make of it at first,'' said Peter Tira, a spokesman for the Department of Fish and Wildlife.
How the nutria got here, no one knows. Nutria are native to Argentina, Brazil and other South American countries. The rodent was imported to the United States in the 19th century for its plush fur, and many escaped into the wild before becoming a hat or coat, but California was believed to have killed off the animal in the 1960s.
Some think the current population represents a lineage of holdouts that went undetected. But most hypothesize that someone brought the nutria here -- again -- despite laws banning their import.
The animal, which is distinguished by its buck teeth, white muzzle and ratlike tail, flourishes because it has few predators in the wetlands and reproduces relentlessly. Females reach sexual maturity as young as three months and have two to three litters annually. One animal and its offspring can give rise to 200 nutria in a year.
Such productivity has allowed the nutria to overrun places such as Louisiana, where sugar cane and rice fields have been decimated and miles of coastal wetlands have been lost. The animal feeds on nearly all aquatic plants and consumes about 25 percent of its body weight each day.
Bounty hunters in Louisiana continue to trap tens of thousands a year. State wildlife officials have even opened publicity campaigns to portray the nutria as a delicacy to get people to eat the animal's lean white meat.
Still, the nutria thrives. Its grit has prompted a New Orleans minor league baseball team to adopt the rodent as its mascot.
The Chesapeake Bay region also has been infiltrated by nutria. Wildlife officials there, however, have done a better job of containing it, partly because the infestation was smaller and they got an earlier start.
After beginning an eradication program in 2002, which has so far cost about $21 million and included up to 19 biologists at any given time, Maryland wildlife officials are about to declare victory. They haven't seen a nutria in three years, after killing off nearly 14,000 over 400 square miles.
``In general, I feel very good about the project,'' said Dan Murphy, chief of habitat conservation for the U.S. Fish and Wildlife Service in Annapolis. ``It's probably the most successful aquatic mammal eradication that's happening in North America.''
The effort began with a far-flung detection program that used ground surveyors, boats, dogs and trail cameras to locate the nutria. Biologists also would sometimes capture an animal, perform a vasectomy and follow it back into the marshes to find the pack.
A coordinated campaign of trapping or shooting the animals followed.
California wildlife officials, who have begun consulting with their counterparts in Maryland, envision a similar response in the Central Valley. The situation here, though, comes with its own challenges.
For one, the region is not as contained as the Delmarva Peninsula along the Chesapeake Bay, which offers natural water barriers on three sides that limit the animal's dispersal. The area where nutria have been found in California also is larger, spanning about 3,000 square miles.
Secondly, California doesn't experience the cold winters that kill nutria on the East Coast.
And finally, California law limits wildlife officials to using traps that don't maim or kill the animal. Leg snares and body-gripping traps, which are less humane but far more effective, are prohibited.
``It's going to be more difficult for them,'' Murphy said. ``They don't have as many tools to use as we have. ... But it can be done.''
The state has begun to work with the U.S. Department of Agriculture's Wildlife Services, an agency known for its skill in killing nuisance animals, and sometimes criticized for its success. But what the partnership will look like and who will ultimately lead the effort remain unclear.
So far, Greg Gerstenberg, a senior wildlife biologist for California's Department of Fish and Wildlife, probably represents the state's best hope of getting on top of the problem.
Having grown up trapping muskrats, Gerstenberg has been working to adapt his methods for capturing nutria. He was helping Cann and Kroeker on their recent outing in the North Grassland Wildlife Area.
``To me, it's a lot like hunting,'' Gerstenberg said as he made the rounds checking traps. ``It's not just about shooting. It's about figuring out the animal. You're trying to understand where they go and what they do so you can outsmart them.''
He parked his Ford Expedition along a dirt road next to a muddy pond. He put on his chest waders before heading into the water. When he arrived at his trap beneath a bed of marsh plants, he tallied another success: a nutria squealing in the steel cage.
He dragged the trap ashore, grabbed his .22 rifle and made the kill.
``If you're going to eradicate them, you have to get every last one,'' Gerstenberg said. ``Right now, we're not keeping up with their reproductive levels. But we got to start somewhere.''