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Besides the coyote, what would you guess is the most problematic type of wildlife in California?

Mountain lions? Hawks? Bears? Landscape-munching, car-wrecking deer?

Wrong. Try pigs.

"They are a major problem in the county," Sonoma County Agricultural Commissioner Tony Linegar said. "We deal a lot in agriculture with problem pig cases."

In 2012, farmers and landowners asked for help from the commissioner's two animal control agents almost 900 times: Coyotes accounted for 736 calls. Pigs came in second with 80 calls, more than twice the number of calls for all other animals combined, including mountain lions, bears, raccoons, and skunks.

The problem with pigs is that they breed prolifically, producing two or three large litters per year, so they can spread across the landscape exponentially. Even worse, they will eat nearly anything they can get their mouths on, from grubs, weeds, and acorns all the way up to small mammals, birds and amphibians.

The pigs, known technically as "feral swine," are the rough and tumble descendants of European and Asian pigs brought to the New World in waves, starting with the earliest Spanish explorers, right up to today's modern pig farmers. Some animals were released deliberately on the land, often for hunting purposes, and others escaped from farms.

Until the 1950s, wild pigs were found only in a few coastal counties in California, but now they have spread to nearly all parts of the state, excepting the driest deserts and coldest mountaintops.

In the East Bay, news outlets reported in September that a herd, known as a "sounder," of at least 20 pigs had devastated yards throughout the suburban city of San Ramon. In San Jose, meanwhile, the problem has become so great that the city council there passed an emergency ordinance in November allowing property owners to shoot the pests inside city limits.

Federal wildlife officials alone report killing more than 32,500 feral pigs in 28 states in 2012, demonstrating that pigs are both common and widespread nationwide.

In Sonoma County, wild pigs are concentrated in the north, but Linegar and others say they are moving steadily south towards Petaluma, Sonoma and Carneros, where they were previously rare.

"They're incredibly wily," said J. Hall Cushman, a biology professor at Sonoma State University who has coauthored several studies of the effects of pigs on the landscape. "They're very, very smart and they have been very adaptable at living on their own" in a variety of environments.

There's no firm number on the amount of economic or physical damage pigs do every year in Sonoma County, but farmers and land managers report that pigs are known to tear through fields, looking for nuts, seeds and grubs. They can plow up crops, knock down grape vines and fruit trees and undermine fences.

"I don't know of a fence that could stop a pig coming through it ... you could do a lot of work to keep them out of your property, but it's very, very expensive," said west county rancher Joe Pozzi, former president of the Sonoma County Farm Bureau and district director of the Gold Ridge Resource Conservation District.

In addition to monetary losses, pigs can cause long-term environmental damage, tearing up ground cover, destroying nests of quail and other native animals, and promoting the growth of invasive non-native plants by disturbing the habitat of native species.

Cushman said there is evidence that the stagnation of native oak forests through much of California might be caused in part by pigs foraging for acorns and tearing up oak seedlings.

Conservationists say the damage can extend well beyond the piece of land the pigs infest.

"My understanding is that they are a fairly significant issue related to water quality," said Craig Anderson, executive director of LandPaths, a land stewardship and outdoors education agency in Sonoma County. "They do a great amount of rooting with that incredible schnoz of theirs," which can lead to erosion into nearby streams and rivers.

LandPaths has an active trapping program on the lands it manages, he said, and Anderson himself has been on hunts for wild pigs, expeditions that gave him great respect for the animals.

"They're very agile, very quick," he said.

Unfortunately for the pigs, there really isn't a nonlethal way to get rid of the animals. Fencing them out is difficult and expensive, since pigs are strong and able to knock down or burrow under most fences. Trapping and releasing them elsewhere is impractical because it just transports a destructive problem from one place to another.

The difficulty of combatting the animals led to an agonizing choice for the Sonoma Land Trust in 2010, when their newly acquired Jenner Headlands preserve suffered an invasion of wild pigs.

"It just exploded suddenly, did a lot of damage," said Bob Neale, stewardship director for the Land Trust. "We felt like we need to act to prevent a wholesale turnover of soils on our property."

But for an organization dedicated to preserving wildlife, the decision to trap and kill the pigs was difficult.

"We thought deeply about it for a variety of reasons," he said. "It would take a lot of effort and expense and we knew it had collateral issues ... we did what we had to do, but we did it as humanely as possible."

Controlling pigs is no easy task. By and large, land managers say, the best way is to trap them in big wire or wooden cages or corrals, but pigs are clever and sometimes spot the traps. And at times when food is plentiful, such as the fall acorn season, they tend to ignore the bait in the traps and munch on wild food in the woods.

The Army Corps of Engineers and Friends of Lake Sonoma host regular pig hunts at the sprawling Lake Sonoma park in the fall and winter, when tourists are not present in large numbers. But, hunters and biologists say, pigs are clever enough to know when they are being stalked and it doesn't take long for them to hide in the woods or even flee for nearby properties where owners might not be as worried about controlling their numbers.

"It takes a coordinated effort," Cushman said. "Usually the most effective is when you get a group of large property and landowners coming together with a gameplan for controlling the pig population."

There are only a handful of cases where pigs have been eradicated from an area, Cushman said, and that those have only been on islands where it has been impossible for the pigs to come back and repopulate.

The best advice from experts is to try to live with the pigs as best you can.

"Try to identify what the attractant is in your area, why the pigs are coming onto your property," said Craig Stowers, environmental program manager for the California Department of Fish and Wildlife office that regulates hunting of game animals. "Remove that resource and they will go away."

That can include securing trash, fencing gardens, or treating yards for grubs and insects.

Often, however, it is not feasible to make a property unattractive to pigs, so landowners just need to be diligent about keeping the pressure on the animals through trapping or hunting to hold the population at a minimum. But, Stowers said, be prepared for a long fight against a relentless opponent.

Pigs "are the smartest animals I have ever been around," he said. "They make a dog or a horse look like a dummy."

(You can reach Staff Writer Sean Scully at 521-5313 or sean.scully@pressdemocrat.com. On Twitter @BeerCountry.)