SIGHTLINE

SUMMER 2001
Vol. 2 No. 1

AIR
The Acid Test

HUMAN INTERACTION
Back to the Future

WILDLIFE
Deviant Behavior

WATER
Aquatic Insects on the Frontline

INVASIONS
Big Hogs, Big Problems

VEGETATION
Managing the Land

BIODIVERSITY
Campaign to Identify Smokies' Species Continues

SIGHTLINE
is published on behalf of
Great Smoky Mountains National Park
by the
Energy, Environment and Resources Center (EERC)
at the
University of Tennessee.

EERC conducts research designed to promote real-world solutions to problems in the fields of energy, environment, technology, and economic development.

.

SIGHTLINE is sponsored by:

Friends of Great Smoky Mountains National Park

and

Great Smoky Mountains Natural History Association

Photos courtesy of National Park Service

SIGHTLINE

SUMMER 2001
Vol. 2 No. 1

AIR
The Acid Test

HUMAN INTERACTION
Back to the Future

WILDLIFE
Deviant Behavior

WATER
Aquatic Insects on the Frontline

INVASIONS
Big Hogs, Big Problems

VEGETATION
Managing the Land

Back to main page

Big Hogs,
Big Problems

Park control of wild hogs protects fragile ecosystems

BY LISA BYERLEY GARY

What's dirty-gray and hairy, is as big as a small woman, and has a musky stench and sharp-pointed tusks? If you're in the Smokies, it might just be a wild hog.

Other than its name and some common genetic heritage, the wild and wily hog has little in common with the smiling pink pig on your bacon package. In fact, the wild hog is a not-too-popular figure in Great Smoky Mountains National Park, where a thriving population causes severe damage to parts of the Park's fragile ecosystem.

A non-native species imported to this area from Germany or Poland around 1912 as prey for hunters, wild hogs have proliferated in the Park to the point of becoming a nuisance, or worse. Controlling them is the job of the wildlife section of the Park's resource management and science division.

Bill Stiver, a wildlife biologist who earned his master's degree in wildlife and fisheries science at the University of Tennessee oversees hog control in the Park through a program of trapping, shooting, and some limited fencing. His work is part of an effort begun in 1959. UT scientists continued extensive studies on wild hog biology in the 1970s and early 1980s, Stiver says. "We learned a lot then. We've already documented their diet, migratory patterns, and reproduction behavior." Well documented, too, is the wild hogs' destruction of native flora and fauna.

Like their tame cousins, wild hogs will eat almost anything, Stiver says-from flowering plants to mushrooms, snails, snakes, small mammals, bird eggs, salamanders, and carrion-but the mast crop (the hard fruits of trees such as oak and hickory) is the mainstay of the wild hog's diet. Unfortunately, mast is also the dietary mainstay for such native species as bear, deer, turkey, and squirrel.

Besides "hogging" the mast crop, wild hogs also create unhealthy "wallows" by rolling around in shallow, damp areas until they've made a round or oval depression. While this wallowing behavior helps keep the glandless hogs cool and removes parasites, it causes some problems as well. Not only do wallow holes contribute to erosion problems that harm native species like the brook trout, they contain bacteria, which can migrate to streams and pose danger to wildlife and humans.

But it is the wild hogs' rooting behavior that causes the most significant damage to the Park. Many plant species, including ones that are rare or that take several years to flower, are eaten, trampled, or uprooted by the rototiller-like action of a foraging hog, Park experts say.

Hazards to Habitat
Wild hogs like to dig in the ground or root with their noses, and a hog's nose is a much more destructive tool than one might think. According to a 1974 Park report, "Much of the hogs' nourishment comes from the underground parts of plants and from animals which inhabit the soil or leaf litter." Of 80 European food plants documented in a 1955 study, wild hogs were found to eat the roots or rhizomes of 49 species, the leaves or shoots of 24, and the fruit of 16. Spring-flowering plants such as star chickweed, fringed phacelia, and Dutchmen's britches are often disturbed by hogs, as are Turk's cap lily, Clingman's hedge nettle, stinging nettle, and jewel weed, says Janet Rock, a Park botanist who tracks rare plant populations. Although the hogs' rooting damage is widespread, certain areas of the Park are of special concern.

"Cades Cove represents an unusual concentration of unique plants," Rock says. For example, "Coastal plain affinity plants-things you'd typically find near the North Carolina or Virginia coast-turn up in Cades Cove." Yet, species such as Virginia chain fern have disappeared from the Gum Swamp area, and purple fringeless orchid can no longer be found in the Abram's Creek floodplain, Rock says, in part because of hogs, though the plants' disappearance may also be attributable to deer. Hogs are somewhat less of a concern now than in the past because the Park's control efforts help keep the population down, Rock says.

Fenced exclosures, which have been used to protect unique vegetation in two wetland areas of Cades Cove for about 20 years, have also been tried in beech gap understories. The wire mesh fencing, which keeps hogs out but is passable for deer and bear, works well "unless a tree falls on it," Stiver says, but it is expensive to install and maintain even in a limited area.

Disease Danger
Wild hogs not only damage plants and contaminate streams, they also pose a potential danger to domestic pigs in the area because of their ability to transmit diseases, Stiver says. The UT College of Veterinary Medicine tested blood serum samples from 195 wild hogs removed from the Smokies between December 1998 and February 2000. All tests were negative or inconclusive.

"I don't know of any instances of disease transmittals in this area so far," says Stiver. "The problem is with people bringing wild swine from other parts of the country and releasing them here. States south of here have problems with pseudorabies and with swine brucellosis in their wild hog populations. Both diseases cause abortion and piglet death, and the swine industry spends millions of dollars to keep [such diseases] out of commercial operations. Tennessee and North Carolina are officially free of both psuedorabies and swine brucellosis; we'd like to keep it that way."

It is illegal to relocate wild swine without proper testing, Stiver says, but the Tennessee Wildlife Resource Agency has received reports of wild hogs from Florida being released near the Park.

Non-native
The first wild hogs in the Smokies area were true wild boars imported as game animals. The 10 sows and three boars were enclosed on a game preserve in Hoopers Bald, 15 miles southwest of the Park, where they multiplied undisturbed until 1920. Then about 100 of them escaped to the mountains where they interbred with feral pigs-domesticated hogs that had escaped from local farmers. The resulting stock looks remarkably like a true wild boar, Stiver says, complete with tusks, a mane, and dark, hairy fur. But an occasional white blaze on a face or white markings on feet give away their mixed heritage. Because the Smokies' hogs are large (males average 125 pounds and four to five feet in length and stand two to three feet at the shoulder) and look like true wild boars, they are popular trophies for big game hunters.

Hunting is not allowed in Great Smoky Mountains National Park, but Stiver says the Park has an agreement with both Tennessee and North Carolina to relocate trapped hogs from the Park onto forest-service land that is open to seasonal hog hunting. Since 1959, of the nearly 10,000 hogs removed from the Smokies, about 4,000 have been trapped and relocated; the rest were killed. The decision to relocate is made on a case-by-case basis, Stiver says, and is largely a practical one. "If a hog is trapped five miles into the backcountry, it's physically impossible to haul it out," he says.

When wild hogs must be euthanized, they are left to recycle back into the Park. Bears, coyotes, turkey vultures, and other scavengers consume them. "When a hungry, undernourished bear emerges from its den in the spring and finds a healthy wild hog carcass, that is very beneficial," Stiver says.

Control Efforts
The wildlife section's permanent staff of five has a combined 60 years of experience controlling wild hogs, and most have a B.S. or M.S. in wildlife biology or a related field. Some staff members also have training and experience in handling firearms and are outdoors enthusiasts. That helps with a job that requires camping alone in the backcountry for several days at a time, Stiver says.

Such work is carried out under strict guidelines and requires a lot of paperwork. "This is a control program because of the impact pigs have on Park resources," Stiver explains. "The work is carried out in a professional manner and as humanely as we can possibly make it. We have protocols for euthanizing pigs in a trap; this is not sport hunting."

Helping the permanent staff are experienced seasonal employees who work six months at a time. In addition, resource assistants from the Student Conservation Association work three to four months at a time. These college students or recent graduates, many of whom have come through the wildlife and fisheries program at UT, get practical experience in resource management while providing a valuable service. "They're a tremendous help for us," Stiver says. "We pay them a small stipend and provide housing. In return they help us with wildlife management, especially with trapping."

Although wild hogs have a reputation for being mean and ferocious, he says, the ones his staff encounters are actually quite skittish. Wild hogs are wary by nature; they avoid human contact whenever possible and forage mostly at night. Despite poor eyesight, their extraordinary senses of hearing and smell make them difficult to catch. "We work at night during the summer with only a flashlight. Many times we'll be within 20 feet of a wild hog. If the wind changes and he catches our scent, he's gone."

While it's unlikely the wild hog will ever be completely removed from Great Smoky Mountains National Park, Stiver says, the removal efforts his section manages help keep the population down. "Park visitors don't encounter as many pigs as people did 20 to 25 years ago, but we encourage them to report any sitings."

For more information, contact Bill Stiver, Great Smoky Mountains National Park, 107 Park Headquarters Road, Gatlinburg, TN 37738, or call 865-436-1251.