Sep 2, 2011

Invasive feral pigs can devastate crops

Feral pigs are a major problem for everyone, not just farmers. Due to a high reproductive rate and a lack of natural predators, feral pigs are quickly becoming a huge nuisance problem in the U.S., causing millions of dollars in damage to agricultural crops and posing a danger to people and animals. Control programs for feral pigs are expensive and time consuming, but essential to protecting valuable habitats and food sources.

Origins and biology

The feral pigs growers and others are dealing with today are non-native descendants of domestic stock brought to the Southeast centuries ago by Spanish explorers, according to USDA. Domestic hogs provided a major food source for early explorers and settlers. Hogs that escaped or were released adapted readily to the wild and prospered in a wide variety of habitats.

Feral pigs are hoofed mammals, generally stocky, with short legs, long snouts, and four continually-growing canine teeth (tusks) that self-sharpen from movement of the upper and lower jaw. They give the boars (males) a very formidable weapon. In northern states like Wisconsin and Michigan, some of the feral hogs are either Russian boars or are crossbred with them, according to the Wisconsin Department of natural Resources. The Russian boars are larger, more aggressive and readily suited to adapt to harsher weather conditions.

The size and weight of hogs varies depending on habitat and genetics. Typically, boars are larger than sows (female pigs) with adults weighing from 200 to 450 pounds. Boars may reach three feet at the shoulder and five feet in length. Average tusk length is three to five inches. Sows are usually 100 to 300 pounds and have relatively small tusks. Feral pigs typically have black, grey, or reddish-brown hair either in solid or mottled patterns.

Feral pigs are omnivorous, opportunistic feeders with diets consisting of just about anything, according to the Arkansas Fish and Game Division (AFGD). They will not only level a vegetable crop, they can also damage fruit trees. The voracious appetites of feral pigs combined with large home ranges cause.

Feral pigs breed year round with peaks in the breeding cycle during fall and spring. Sows are sexually mature at six months, but typically begin breeding at one year of age. Gestation lasts 115 days with an average of two litters per year. Litter size ranges from four to 14 with an equal sex ratio, AFGD said.

Spread and control measures

According to both USDA and the U.S. Fish and Wildlife Service, feral pigs range from South Carolina to California and as far north as Wisconsin and Canada. Illegal trapping, transport, and release of feral pigs are a major cause of population expansion and movement across the United States. Recent studies reveal feral pigs populations in at least 44 states and Canadian provinces.

Feral pigs have higher than average survival rates due to a lack of natural predators in most areas. Humans are the main predators of feral pigs, as hunting of the species is very popular and is the only real control measure according to USDA. Control and eradication programs for feral pigs include trapping, shooting, running with dogs, and hunting with the aid of bait.

"It is safe to say that feral hogs occur throughout Florida," said Scott Hardin, Exotic Species Coordinator, Florida Fish and Wildlife Conservation Commission. "Their numbers ebb and flow in response to hunting pressure, other management and rain conditions. In most of Florida there is no daily bag limit or size limit and hunters can play an important role in keeping the population down. However, pigs are very fertile and their abundance rebounds quickly. In some sensitive wetlands areas, special trapping or shooting is used to limit damage."

USDA's Animal and Plant Inspection Service Wildlife Services (WS) division published wildlife damage management plans for each state and several looked at wild pigs.

In New York, feral pigs have slowly been increasing in abundance during the last few years. Most feral pigs sightings are associated with regulated shooting enclosures. However, other feral pigs sightings are independent of shooting enclosures. USDA, farm organizations and food safety advocates have concerns about feral pigs spreading disease to livestock and people, contaminating the food supply with bacteria, damaging wetlands, and threatening populations of native wildlife.

At the requests of New York State Department of Agriculture and Markets, WS conducted a survey to document locations where feral pigs occur, captured feral pigs and took tissue samples for disease monitoring to alleviate damage to crops and wetlands. WS surveyed 9 counties that border Pennsylvania by interviewing 968 landowners about feral pigs. 27 feral pigs were captured and tested for pseudorabies and pig fevers. The state is using the information to make policy and regulatory decisions about managing a growing population of feral pigs according to the USDA report.

In Texas, requests for feral pigs damage management continue to increase each year as a result of the viability and range expansion of feral pigs and their adverse impacts on multiple resources. Additional funding will be required if Wildlife Services' operational and research efforts can begin to get a handle on this expanding resource problem.

"I've seen some fields that were pretty tore up by hogs," said Georgia grower Herb Siegler. "It depends on where the fields are, though. On my fields, we see more damage from deer than hogs."

Arkansas WS officials believe that because of illegal translocation of feral pigs, the feral pigs population has increased throughout the state, resulting in serious ecological damage The USDA report said. In cooperation with the Arkansas Game and Fish Commission, various population reduction strategies are being evaluated. Feral pigs problems are increasing at an alarming rate in the absence of enforcement of regulations, which could restrict their movement.

Michigan hasn't escaped the feral pig plague either. There are currently 32 counties in the state with reported pig sightings or pigs being killed. The state Department of Natural Resources asks that anyone who sees a feral pig to report its location. As in most states, feral pigs in Michigan are listed as a nuisance species and are open to hunting year round by any licensed hunter.

California's Department of Fish and Game classifies feral pigs as a game animal in the hopes that hunting pressure will reduce the overall population. Feral pigs were at the root of at least one E. coli problem at a vegetable field in the Salinas Valley area.

All of the state WS services agree that the best control measure is removal and elimination. Where hunting is allowed, there have been decreases in the numbers of pigs. In urban areas and close to homes, trapping has shown to help.

One way to deal with feral pigs has made for popular television. Trapping pigs in areas where hunting isn't a viable option and has made for several shows on the Discovery network. The shows, such as Hogs Gone Wild, depict the trapping of pigs. The pigs are then turned over to food banks.

If you have a feral hog problem, contact your state wildlife or agriculture department. More information about state wildlife control plans is available at the USDA website.

By Derrek Sigler, assistant editor