“How fast do they spread? It’s usually 70 miles per hour – the speed of trucks on an interstate highway,” the Savannah River National Laboratory scientist said.
First domesticated 10,000 years ago, hogs arrived in North America with explorers around 1493, he told members of the CSRA Fly Fishers during a presentation last week.
“For a long time, including most of the 20th century, the population was pretty stable,” he said. “But after 1989, it all changed.”
Since then, the creatures have spread rapidly and now exist in 47 states – despite increasingly sophisticated efforts to control them.
Why did a once stable population suddenly explode?
“Very simply, it’s because they became the second most popular big-game animal in the country, behind whitetail deer,” Mayer said.
Hunters in many regions quickly realized how simple it was to acquire and release hogs into new habitat where they can be hunted.
“So even though it is illegal in every state, people would just go out, get a trailerload of pigs and turn them loose,” he said. “That’s all they needed to do. The pigs did the rest.”
Compounding the problem was the proliferation of fenced shooting preserves, where wild boar could be “hunted” by paying clients. Today, there are about 1,000 such operations, from which hogs frequently escape and establish new populations.
Today, the crop-crushing, wetlands-wallowing, tree-girdling creatures are responsible for about $1.5 billion in damages each year.
Mayer, who has studied feral hogs more than 30 years and served as lead consultant for National Geographic Explorer’s 2005 hourlong special on “Hogzilla,” said pigs are as remarkable as they are destructive.
“They can live anywhere, from Canada to the Central American jungle,” he said. They can become reproductively mature as early as three months and can produce multiple litters each year.
They are also becoming more and more common in urban areas, where conflicts with humans are more frequent. “They are moving into urban areas and we have them in Charlotte, Dallas, Houston, San Antonio,” he said. “They’re wandering around and rooting up parks, greenways – even golf courses.”
Controlling feral hogs is a challenge with few solutions.
“There are really just two options,” he said. “Kill them or exclude them.”
At Savannah River Site, he said, efforts to control them have been under way for decades, and there are still plenty of pigs.
Because they reproduce so rapidly, 50 to 75 percent of the population in a given range must be removed each year – just to stabilize the herd or begin to reduce it.
“So for a herd of 1,000 pigs, you’d need to kill 700 each year for nine years,” he said, adding that traditional hunting rarely kills more than 20 to 25 percent of the population.
Today, eradication tactics include trapping, dogging with trained hounds and the use of airborne marksmen who exterminate them from helicopters known as “pork choppers,” he said.
Research also remains under way for chemical solutions to the feral hog problem. Future options may include immuno contraceptives to halt reproduction while existing animals are removed; and possibly a toxicant that would be fatal to hogs but would not affect other wildlife.
Although hogs remain a popular big game animal to hunt, their problems vastly outweigh the benefits, he said, noting that their mere presence often pushes another popular game animal – the whitetail deer – out of the area.