Blue states and red states were the subject of a talk by Jack Mayer of the Savannah River National Laboratory in Aiken, South Carolina.
But Mayer wasn’t discussing partisan politics. Rather, he was discussing the spread of wild pigs. On a large map displayed behind the podium as Mayer spoke to a crowd at The Wildlife Society’s annual convention last month, held in Waikoloa, states (including Hawai`i) with established populations of wild pigs were colored in red. Those in blue had wild pigs numbering in the hundreds or thousands in some counties. The handful of northern states colored in yellow don’t – yet – have known populations of free-ranging wild pigs, Mayer said. They included Alaska, Montana, Maryland, Connecticut, Vermont, and Maine.
Today’s map represents a progression, Mayer said. “The states in yellow are where states in blue were in the 1980s. And the states in blue are where the red states were in the early 1990s,” he said. The message? “Take the wild pig situation very seriously,” he warned.
To judge by the standing-room-only crowd in the conference room, wildlife managers from across the country, as well as in Hawai`i, are already doing just that.
As an example of how rapidly wild pigs can spread, Mayer cited the case of Oklahoma. “In 1982, wild pigs were found only in a couple of counties in the southeastern part of the state,” he said. According to one estimate, they numbered in the hundreds, maybe even up to 1,000, Mayer said. Authorities at the time considered the population stable to decreasing, and, he said, they assumed deer hunters would take care of the pigs.
Twenty-five years later, the southeastern part of the state had pig densities of 64 or more per square mile, but there remained three Oklahoma counties with no pigs, Mayer added. Four years later, and wild pigs are in every county. “We currently estimate there are half a million wild pigs in Oklahoma – maybe as many as 1.4 million,” he said.
The same scenario played out in Michigan, which is still colored in blue on Mayer’s map – though perhaps not for long. The first report of a wild pig was made in 1986, he said, but it took more than a decade for state officials to become concerned about the problem. Today, he said, 65 of 83 counties in Michigan have wild pigs.
In the 1980s, the total wild-pig population in the continental United States was estimated at between 500,000 and 1 million. But, he noted, “some of those estimates were pretty sketchy.” The good news, he said, “is that many of the statewide estimates have improved. The bad news is that the numbers have gone up, to between 3 million and 8 million wild pigs in 2011.”
In that same time interval, he went on to say, wild pigs “have become the second most popular big game animal in North America,” which poses a “conundrum: one of the worst invasive species on the planet is also one of the most popular game mammals on the planet, on every continent except Antarctica.”
Their spread northward in the United States was not an altogether natural expansion of their range, he noted. “Hunters who wanted to hunt premier game animals but didn’t want to drive south figured out something: all they had to do was trap pigs and move them north. Or, if they didn’t want to trap them, they could purchase them from people who did.”
“It’s completely illegal, but that hasn’t stopped anyone.”
Once pigs become established, they’re difficult to contain. When it comes to their reproductive potential, he said, “nothing else their size or larger can compete with the pig in its ability to crank out babies.” Not only do they start young, females can produce two litters a year, and continue to produce piglets for the rest of their long (ten years or more) natural lives.
One of the difficulties in dealing with the growing problem is the lack of uniform regulations. “This is not a plan for success in a national crisis,” Mayer said. “Are they invasive? Should we talk about eradication or damage control? Should we make sport hunting illegal everywhere?” he asked. “It’s time to make a decision.”
Michael Bodenchuk of the U.S. Department of Agriculture’s wildlife services office in San Antonio spoke of the damage wild pigs do to natural resources and agriculture. “They’re a train wreck – just one thing slamming into another,” he said.
They damage crops: “Each day, they have to consume 3 to 5 percent of their body weight.” They’ve virtually eliminated the Texas peanut industry, he noted, and through their rooting damage, they have reduced harvests of corn and hay. They carry disease to domestic livestock. They can contaminate produce with pathogens such as E. coli, leptospirosis, and toxoplasmosis. Sheep and goat production areas can lose up to 40 percent of lambs to predation by wild pigs, he noted.
The total damage to Texas agriculture, he said, ranges from between $80 and $828 for each wild hog. Hunting alone cannot begin to control the pigs, he said: “Aerial gunning is the most cost-effective control measure.”
Billy Higgenbotham, with the Texas A&M Extension Service, told the audience of his plan to eradicate wild pigs: “I’ve got the answer, and we could do it tomorrow,” he said. “Institute a two-hog limit and a two-day season, and we’d poach `em off the face of the Earth.”
But constrained to legal removal methods – shooting, trapping, snaring, and catching with dogs – “all you’re going to do is manage pigs,” he said, not reduce their numbers.
For landowners and wildlife managers, Higgenbotham recommended trapping – “a process, not an event.” He outlined his approach to corral traps, which includes a long, patient process of baiting and monitoring. (For more, see: http://feralhogs.tamu.edu.)
The process is effective, he said. In Texas, ranchers and farmers using traps remove nearly half a million hogs a year. As an added boon, in Texas, at least, the wild pigs can be sold, live, allowing ranchers to recover at some part of their costs, he noted.
Volume 22, Number 6 — December 2011