Feral swine spread comes with billion-dollar price tag
One bullet for one boar makes for poor hunting odds. In 1984, on the trail of a tracking receiver in the woods of South Carolina, Jack Mayer caught sight of radio-collared wild pig No. 20, drew a bead and squeezed the trigger. The lead ripped through the shoulder, bounced up across the neck, and deflected into the lower mandible, severing the jawbone in half.
The pig wheeled around, charged one of Mayer’s fellow researchers up a tree, and dashed into deep cover and the relative safety of a lost radio signal. A year later, checking a wild turkey food plot at sunset, Mayer walked up on a large boar gorging on feed corn. He quietly slipped in and fired, dropping the boar in the middle of the plot. A Lazarus beast beneath his feet, Mayer had finally killed No. 20.
The subsequent necropsy revealed the trajectory of Mayer’s initial slug. Incredibly, No. 20 had entirely healed and gained weight after the shooting. Any other animal with a gaping wound, mangled body tissue and broken jaw would have starved to death, yet No. 20 had survived and thrived.
The wild pig bomb has detonated, ripping and rooting billion-dollar scars across farmland every year. The search for a silver bullet has come up empty, and the past 30 years have seen a wild pig presence balloon from 19 states in 1985 to more than 40 states in 2016. High-end estimates of 11 million wild pigs make warnings of impending invasions mostly moot: The porcine beasts have already set up shop. However, with new trapping techniques in hand and promising control tools on the horizon the means to halt wild pig advances might soon arrive.
Mayer places the U.S. wild pig population at 6.3 million, with an overall range of 4 million to 11 million. Prior to 1990, when total population might have been as low as 500,000, wild pigs typically expanded along drainage corridors in the South. They began moving into northern states in the 1990s, escaping from commercial fenced shooting operations or intentionally released for hunting. Just a handful of wild pigs set loose on virgin land is akin to pouring water on gremlins. With no effective predators other than humans, wild pigs are permanently on the cusp of a population explosion.
They breed year-round and sows produce two litters per year—six piglets on average, but litters can be as large as 12 piglets. Between 24 to 48 hours before giving birth, sows construct a farrowing nest to provide protection and insulation; newborn piglets are particularly challenged with body temperature regulation. The rooted-out area resembles a giant bird nest, but sows sometimes craft a roof over the top by building a pile of debris and burrowing inside.
“We’re talking about an animal with exceptional intelligence, easily on par with dogs,” Mayer says. “In some cases and exercises, wild pig intelligence matches with chimpanzees.”
Sows conceive as early as three months and boars are sexually mature at five months.
“These animals can put more little feet on the ground than any other free-ranging mammal in North America their size or larger,” says Mayer, one of the foremost wild pig experts in the world and manager of the Environmental Sciences and Biotechnology Group at the Savannah River National Laboratory in Aiken, S.C.
The average wild pig age is 1.5 years, with the oldest animals living 8 to 10 years. Sows and litters run together, often in multiple groups, but mature boars tend to be solitary except during breeding. Boars average 200 lb. (but can reach up to 500 lb. to 600 lb.) and sows average 170 lb. They can run at speeds nearing 30 mph and cross rivers or lakes with ease. Movement depends on environment. With water, food, shade and escape cover, they’ll remain relatively confined. Northern expansion is limited by hard permafrost due to rooting or forage requirements, and wild pigs can’t survive beyond permanent snow cover. Those academic details are no comfort to U.S. farmers: Wild pigs can survive in all the lower 48 states.
An opportunistic omnivore with no peers, wild pigs are tailor-made farmland marauders. Crops are an open pig trough, particularly in tandem with the irrigation sources many farms provide. They eat 3% to 5% of total body mass daily, and are decidedly herbivorous with 80% of diet composed of vegetation from grass, leaves, fruit and fungi, according to Mayer. Animal material makes up 10% to 15% of diet: larvae, earthworms, amphibians, fish, eggs and small animals. They also ingest miscellaneous items such as dirt and sticks.
“They consume up to 300 different food types. If it has a calorie in it and wild pigs can get their mouth around it, they’ll eat it,” Mayer says.
Their ability to root and tear up ground is phenomenal. A pasture hit overnight can appear to have been cluster-bombed, with knee-deep holes pocking a field. Phenomenal diggers, an hourglass nasal bone floats in cartilage to provide backing for the nasal pad, enabling wild pigs to lean in when rooting with strong neck muscles. “They can use the snout to literally open cracks in concrete,” Mayer describes.
The same snout that serves as a porcine front-end loader is also highly sensitive to smell, picking up scents from five to seven miles away. “A grain crop ripens and pigs show up from all directions,” he notes. “It’s not just surface smells. We’ve got documentation showing scent detection at up to 25' below the surface.”
Can the march of a beast with no Achilles’ heel be stopped? Dale Nolte is the national coordinator for the National Feral Swine Damage Management Program (NFSDMP) and leads USDA’s nationwide effort to reduce the impact of wild pigs. The survival of wild pig populations means a persistent bleed on farm
profits. Nolte believes damage inflicted by wild pigs across the U.S. economy might be as high as $2.5 billion per year, with roughly $1 billion of the total exclusive to agriculture.
In 2014, Congress provided funds to NFSDMP to minimize damage inflicted by feral swine. In states where feral swine are emerging or populations are low, USDA is cooperating with local and state agencies to implement strategies to eliminate them.
“We believe feral swine have been removed from six states,” Nolte says, “but we need to continue monitoring efforts to detect any that might have been missed or reintroduced.”
Trapping technologies are becoming increasingly effective and USDA is developing contraceptive and reproductive inhibitors, along with sodium nitrite to be used as a toxicant. Pending EPA registration, Nolte expects an oral toxicant might be available within four years.
As a supervisory research wildlife biologist with USDA’s National Wildlife Research Center (NWRC), Kurt VerCauteren advocates for a sledgehammer approach to wild pig eradication. “A landowner needs to hit hard against wild pigs. Traps are consistently improving with remote technology,” he says.
Aerial gunning studies point toward the efficacy of a consecutive three-day hunt to wear down a wild pig population and usher in a long phase of rebuilding, VerCauteren notes. Single day hunts, spaced throughout the year, allow time for pig numbers to bounce back rapidly. He suggests a multi-pronged control strategy, with all methods in complement.
VerCauteren serves as head of NWRC’s Feral Swine Research Project, and his research team is conducting pen studies to test the efficacy and safety of sodium nitrite. He has submitted an application package to EPA, and following field studies, projects licensing for an oral toxicant by 2020. Further on the horizon, VerCauteren hopes to deliver oral contraceptives in pig-specific feeders.
NWRC typically works with universities, research institutions, counties and states to boost wildlife populations, but regarding wild pigs, the effort is a near reversal. Experts in physiology, biology, ecology, control, baiting and economic modeling are teaming with chemists and registration specialists for EPA in an unprecedented multi-disciplinary approach to wild pig control.
“We’re on the front end of this effort and have weapons in hand,” VerCauteren says. “In our generation, we’re going to control them where they aren’t established. In states with heavy wild pig populations, we want to at least decrease the financial cost of their presence.”
“In the past, little attention was paid to feral swine,” Nolte adds. “Now we have a major problem from Florida to Canada and most states want them gone or to at least reduce the damages.”
The cost of wild pig damage to the agriculture industry is staggeringly high, but Mayer warns the impact could be far greater. When a rogue group of hunters loads up a trailer of wild pigs for clandestine transport, the risks go beyond damage to crop rows. “If we had a foreign animal disease outbreak that got into wild pig populations and then into our livestock, the cost could reach into the hundreds of billions of dollars,” he says.
Control efforts require a pace to match prolific breeding, and 50% to 75% of the pig population must be killed each year to keep population in check. That’s an extremely tough task for any afflicted state. Even if a toxicant arrives by 2020 and an oral contraceptive follows on its heels, Mayer remains uncertain about wild pig population projections.
Wild pigs have become part and parcel of the agriculture equation, a financial drain with no signs of abatement. “We have a problem in this country and I don’t know what the answer is,” Mayer says, “but we’ve got to stem the tide and no single tool will work alone. There is no silver pig bullet.”