Invasion of the feral pigs

Feral pigs are invading New Mexico and other Western states, but biologists are working hard to stop them.

  • In Quay County in the spring of 2010, biologist Justin Stevenson documented feral pigs interacting with cattle for the first time in New Mexico. He says they were "close enough for nose-to-nose transmission" of diseases like pseudorabies and swine brucellosis.

  • From a high point in the Quay Valley earlier this summer, Ron Jones uses a receiver to check four traps he had set.

    Ron Jones
  • Bureau of Land Management wildlife biologist Randy Howard, and USDA wildlife specialist Shannon "Bubba" Punnel, release a "Judas" pig after tagging its ear with a transmitter in southern New Mexico's sand dune country.


About six years ago, Ron Jones got the phone call that changed his career. It came from a rancher just east of the barely there town of Quay, N.M., but that wasn't the unusual part. As the local agent for Wildlife Services, a U.S. Department of Agriculture predator control outfit, Jones gets calls from ranchers all the time, typically involving troublesome coyotes, bobcats or skunks.

But this rancher had a different bone to pick. For some 50 to 75 yards, the dusty road to his home was pockmarked with cavities up to four feet wide. He was sure of the culprit: hogs gone wild.

"I told my wife, 'This guy is smoking something -- there's no hogs in this county!' " Jones recalls, chuckling. "I've caught hogs ever since."

It's not easy. Pigs are among the smartest mammals. Shoot just one hog in a feral group of five, and the remaining four will become even harder to catch -- "super pigs," they're sometimes called. In New Zealand, in an area where aerial gunning was common, feral pigs were seen playing dead in plain sight when a helicopter flew overhead, according to one hog expert. The snipers figured they were casualties of a successful mission. When they circled back, though, most of the "dead" had vanished: Score one for the super pigs.

Jones tries not to create such sharp-witted swine. "I don't want to catch just one," he says. "I want to catch 'em all." He points to a patch on his government uniform: " 'Protecting New Mexico's Resources.' That's what we're doing."

The actual ecological and economic messes feral pigs are making in Quay County -- or any of the 17 New Mexico counties where they're known to live -- remain uncertain. That they're appearing here at all, however, is cause for alarm. They're "one of the worst invasive species on the face of the earth," according to Jack Mayer, a feral pig expert with the Savannah River National Laboratory in South Carolina. Others use similarly blunt terms. "They damage everything," says Richard Engeman of USDA's National Wildlife Research Center. In Texas, where hogs number in the millions, conservative estimates put agricultural losses to hogs at $52 million a year; the environmental damage they cause is not well quantified. And they've become an urban problem as well as a rural one: Golf courses and suburban lawns, it turns out, are suitable hog habitat, too.

Thirty-seven states have established populations, up from 19 in 1990. A handful in the West --  including Arizona, Idaho, Oregon, Colorado -- are just beginning to grapple with the problem. "We're all on the small end of the boat when it comes to numbers," says Justin Stevenson, a ringleader for hog control in New Mexico, and until recently, its USDA wildlife disease biologist. These states have an opportunity that others, such as Texas and California, lost years ago. With sufficient funding, manpower, and perhaps a few new weapons, local or statewide eradication may be feasible -- but possibly not for long.

The first domestic pigs came to the U.S. on the boats of Spanish explorers. Swine were carted along as hedges against starvation and to seed New World settlements. They could be unruly companions. When pigs went feral in the West Indies, they "often attacked Spanish soldiers hunting rebellious Indians or escaped slaves, especially when ... cornered," writes Mayer in Wild Pigs of the United States.

In 1539, Hernando de Soto brought a gaggle of hogs to Florida; then he marched through the Southeast, shedding escapee swine along the way. By 1562, Florida Indians were hunting established wild populations. A few years later, a Spanish crew brought over 400 more, and so on.

Back then, and on Western homesteads centuries later, pigs often roamed freely and were hunted when meat was needed. Today, many feral pigs are descended from these free-range domestics. Others are part Eurasian wild boar, released in some states for sport. Some have pure Eurasian lineage, and all belong to the species Sus scrofa.

They are a hardy and adaptable bunch, with undiscerning  appetites: ground-nesting bird and turtle eggs, frogs, lizards, acorns, tubers, grubs. Their foraging snouts turn ground upside down, facilitating weedy invasions. They degrade water quality, and decimate and contaminate crops. (Feral pigs were partly to blame for the 2006 E. coli outbreak in California's spinach fields.) They carry diseases such as pseudorabies, which can be fatal to livestock, and swine brucellosis, which gives humans a flu-like illness and causes abortions in animals. Feral hogs have few natural predators. And they are piglet-making machines: Studies show a population must be culled by 50 to 70 percent annually just to remain level.

Conventional wisdom used to be that once you had feral hogs, you were stuck with them. The same thinking applied -- and in many cases still does -- to many invasive species, whether mammal, plant or mollusk. Eradication efforts are expensive and biologically complex. And some infamous failures have made them politically risky. (A long and pricey campaign to eliminate fire ants from the Southeast in the '60s and '70s was more effective at wiping out the ants' predators. Biologist E.O. Wilson dubbed it "the Vietnam of entomology.")

But an increasing number of successful counterinsurgencies in recent decades, particularly against island-invading mammals, have begun to shift attitudes. In 2006, for instance, feral goats were wiped off the largest island in the Galapagos using sophisticated "Judas" techniques, which employed artificially sexed-up but sterile females wearing radio collars to lead gunners to the last holdouts. "With each (eradication) that's successful, people think, 'Why can't we do this one, and that one?' " says Dan Simberloff, a University of Tennessee professor.

Pigs have also been eradicated from islands and some inland locales, most notably in the U.S. from Santa Cruz Island off the California coast in 2007. Because of the island's size and rugged terrain, "most people said we couldn't do it," says Norm Macdonald, president of Native Range (then called Prohunt), the private contractor hired to do the job. But it was relatively straightforward, he says: After fencing the island into five zones, they used traps and aerial shooting to remove most of the population, then hunted with dogs and released Judas pigs. The team killed 5,036 hogs, most in a little more than a year.

Enthusiasm for bigger and tougher eradications has been slower to reach the mainland due to technical, financial and political constraints. Killing animals, even invasive ones, invites controversy. But some states with relatively new, small or isolated colonies are beginning to accept the challenge. Kansas has already eradicated four local populations, and the rest could be purged from the state within two years, says John Johnson, one of two USDA wildlife biologists charged with eradication there. In 2006, Oregon's Invasive Species Council advised lawmakers to dedicate $1.29 million over four years and $50,000 annually after that to eliminating hogs. The Forest Service just floated an eradication proposal for the Cleveland National Forest in California. And a group of state and federal agencies finalized New Mexico's eradication plan last fall.

These schemes follow a basic tenet of invasive species management: If you can't keep interlopers out, find them early and attack aggressively. In practice, though, it's not easy to do. Pigs, like many invasives, leave evidence of their presence: wallows, rubbed trees, rooted ground. "But likely as not, you're not going to see any pigs," says Mayer. "(People think) it must not be a problem. That's not the case."

In New Mexico, Jones had been pursuing pigs for three years when Justin Stevenson arrived to start his USDA job in 2008, fresh off a gig in Oregon, where he saw hog havoc first-hand. He and Jones began working together, and their shared porcine passion evolved into friendship, earning them buddy-movie nicknames from their colleagues. "I'm Boss Hog," Jones says when we meet, a playful grin flashing beneath his well-kept handlebar mustache. Stevenson, who at 38 is more than two decades Jones' junior, goes by Little Piggie.

A 5-square-mile hog stronghold in Quay County has been their laboratory for testing control methods. Stevenson, a voracious consumer of global hog research, has tried to ensure they follow best practices to the extent finances allow. They've begun using automated deer feeders to bait traps, and Jones uses motion-sensitive cameras to track pigs' movements, waiting until a group habitually enters a trap to set it, which increases his odds of taking whole groups at once. He uses radio telemetry to check whether traps have been tripped, reducing his driving distance significantly. He's convinced ranchers to put up cash for the occasional aerial gunning mission. And he's released Judas pigs outfitted with tracking devices. These new techniques and technology, and a few years' practice, have helped increase Jones' success: Since last October, he says, he's removed nearly 120 pigs, more than double what he took in previous years.

Yet the pig population still seems to grow. No one has a handle on its actual size -- in Quay County or statewide -- but signs are more widespread, and sightings more frequent. Hog work now consumes more than half of Jones' time. "I think we're to the point of living with them," Jones says. To him, the question has become: "Just how much are we willing to give?"

Stevenson doesn't see it that way. He admits they're at a disadvantage as long as Jones is a one-man army. "But if we had 15 Rons, we could eradicate them (in Quay County)," he says. "No question. It just takes coordination."
It also takes money, which is scarce everywhere. Not a single federal or state dollar -- or job -- is dedicated just to hog management in New Mexico. Nor has funding materialized to implement Oregon's pig plan. "The problem doesn't look severe enough yet," says Stevenson. Wildlife Services, the main agency doing active control in New Mexico, has asked staff to cut travel by 20 percent this year. For employees like Jones, that means less time devoted to chasing hogs.

Some regulatory progress has been made. As hogs' popularity among hunters has grown, so has their reach. People pluck pigs out of one place and release them elsewhere to increase hunting opportunities. In 2009, New Mexico banned commercial hog hunting, removing the financial incentive to establish sport populations. Transporting or releasing feral swine was also outlawed. Still, last fall, pigs were discovered for the first time in the Rio Grande Valley bosque, lush riparian habitat where they will be difficult to find, much less eliminate. "That marked a 100-mile migration we know they didn't make on their own," Stevenson says.

"You've got people trying to eradicate them, and right next door, people trying to increase them," says Mayer of most states' conundrum. "I'm not sure how you win a game like that." Scientists are working on toxicants with a pig-specific delivery system and contraceptives. Either would give people a big leg up in the swine wars, but both are five to 10 years out, maybe more.

Ironically, the luckiest break for swine control in New Mexico so far has been the discovery of hog activity in sand dune lizard and lesser prairie chicken habitat around Roswell. Both are candidates for the endangered species list, and though no one has documented hogs snacking on either, their proclivity for herps and birds' eggs makes it likely. Oil and gas operators are funding projects to prevent both species' further decline through a candidate conservation agreement. Next year, the fund will give $50,000 to the Bureau of Land Management and Wildlife Services for hog removal in those species'  habitat -- the first source of dedicated funding for control efforts in the state.

At this point, the ultimate threat pigs pose to the West's wildlife, agriculture and environment is hard to project. Mayer believes pigs will eventually inhabit all 50 states. But public education and a vigilant response could help protect the Intermountain West, which is still mostly hog-free. A group was detected in Idaho's Bruneau Valley in 2009, but state officials think aggressive hunting wiped it out. Wyoming doesn't have pigs, but passed a pre-emptive law in 2009, authorizing state officials to kill them should they show up. Arizona is keeping an eye on its nascent population, but doesn't actively manage them. Colorado has worked cooperatively with Kansas and Oklahoma to control pigs in the southeast corner of the state.

In desert environments, feral pigs face at least one major limitation. "If we're going to win in a particular county or region, we're gonna win based on lack of water for those pigs," says Stevenson. There's more water out there than you might think, thanks to agricultural improvements like stock tanks. But their placement is known and could be manipulated, if used seasonally by cows.

Sitting in his "office," the cab of his government-issued Ford F-250 pickup, Jones scrutinizes photos downloaded from a remote camera. For a few weeks, he's had it trained on a corral-shaped trap that sits empty, strewn with corn, near his parked truck.

"Man alive, I can't believe it," Jones says. The picture trail shows Jones setting the trap at 12:40 p.m. the previous day. For a few hours after that, all was quiet. Then, at 4:18, his targets wandered into the frame: a group of six or so feral pigs that had visited the unset trap twice before. But this time, they didn't go far enough to trigger the trap door. Just six minutes after arriving, they were gone.

"Something spooked these pigs off the trap," Jones says. "See this one running? He's in a hurry." Whatever it was -- a rancher moving his cows, a coyote -- Jones shrugs it off. "Guess what? They'll be back."

This story was funded by a grant from the McCune Charitable Foundation.

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