WILD PIGS

Identification
Wild pigs (Sus scrofa) include both feral hogs (domestic swine that have escaped captivity) and wild boar, native to Eurasia but introduced to North America to interbreed with feral hogs. Like domestic hogs, they may be any color. Their size and conformation depend on the breed, degree of hybridization with wild boar, and level of nutrition during their growing period.

Wild boar have longer legs and larger heads with longer snouts than feral hogs. The color of young boar is generally reddish brown with black longitudinal “watermelon” stripes. As the young develop, the stripes begin to disappear and the red changes to brown and finally to black. Both the male feral hog and wild boar have continuously growing tusks. Wild boar and feral hogs hybridize freely; therefore, the term wild pig is appropriate as a generic term for these animals.

Range
Christopher Columbus first introduced members of the family Suidae into North America in 1493 in the West Indies. The first documented introduction to the United States was in Florida by de Soto in 1593. More introductions followed in Georgia and the Carolinas, which established free-ranging populations in the Southeast. Free-ranging practices continued until they became illegal in the mid-twentieth century. Populations of unclaimed hogs increased and spread throughout the Southeast. Domestic hogs were released in California in 1769 and free-ranging practices there also resulted in a feral hog population. European wild boar were released at Hooper Bald, North Carolina, in 1912, and from there introduced to California in 1925.

Wild pigs are found throughout the southeastern United States from Texas east to Florida and north to Virginia; and in California, Hawaii, Puerto Rico, and the Virgin Islands. The local introduction of these animals for hunting purposes occurred in North Carolina, Tennessee, Texas, Louisiana, and California. The National Park Service reports feral hogs in 13 National Park Service areas. They occur in many state parks as well. Feral hogs are also found in Hawaii, Australia, New Zealand, and several other South Pacific Islands.

Habitat
A variety of habitats, from tidal marshes to mountain ranges, are suitable for wild pigs. They prefer cover of dense brush or marsh vegetation. They are generally restricted to areas below snowline and above freezing temperatures during the winter. Wild pigs frequent livestock-producing areas. They prefer mast-producing hardwood forests but will frequent conifer forests as well. In remote areas or where human activities are minimal, they may use open range or pastures, particularly at night. During periods of hot weather, wild pigs spend a good deal of time wallowing in ponds, springs, or streams, usually in or adjacent to cover.

Food Habits
Types of food vary greatly depending on the location and time of year. Wild pigs will eat anything from grain to carrion. They may feed on underground vegetation during periods of wet weather or in areas near streams and underground springs. Acorns or other mast, when available, make up a good portion of their diet. Wild pigs gather in oak forests when acorns fall, and their movements will generally not be as great during this period. In the winters of poor mast years, wild pigs greatly increase their range and consume greater quantities of underground plant material, herbaceous plants, and invertebrates. Stomach analyses indicate that wild hogs ingest flesh from vertebrates, but the extent to which animals are taken as prey or carrion is not known. Wild pigs are capable of preying on lambs, as well as goat kids, calves, and exotic game.

General Biology, Reproduction, and Behavior
Wild pigs are intelligent animals and readily adapt to changing conditions. They may modify their response to humans fairly rapidly if it benefits their survival. Wild boar have a greater capacity to invade colder and more mountainous terrain than do other wild pigs. Feral hogs feed during daylight hours or at night, but if hunting pressure becomes too great during the day, they will remain in heavy cover at that time and feed at night. In periods of hot weather, wild pigs remain in the shade in wallows during the day and feed at night.

The wild pig is the most prolific large wild mammal in North America. Given adequate nutrition, a wild pig population can double in just 4 months. Feral hogs may begin to breed before 6 months of age, if they have a high-quality diet. Sows can produce 2 litters per year and young may be born at any time of the year. Wild boar usually do not breed until 18 months of age and commonly have only 1 litter per year unless forage conditions are excellent. Like domestic animals, the litter size depends upon the sow’s age, nutritional intake, and the time of year. Litter sizes of feral hogs in northern California average 5 to 6 per sow. Wild boar usually have litter sizes of 4 to 5 but may have as many as 13.

Damage and Damage Identification
Wild pigs can cause a variety of damage. The most common complaint is rooting (sometimes called grubbing), resulting in the destruction of crops and pastures. Damage to farm ponds and watering holes for livestock is another common problem. Predation on domestic stock and wildlife has been a lesser problem in North America.

Damage to crops and rangeland by wild pigs is easily identified. Rooting in wet or irrigated soil is generally quite visible, but can vary from an area of several hundred square feet (m2) or more to only a few small spots where the ground has been turned over. Rooting destroys pasture, crops, and native plants, and can cause soil erosion. Wallows are easily seen around ponds and streams. Tracks of adult hogs resemble those made by a 200pound (90-kg) calf. Where ground is soft, dewclaws will show on adult hog tracks.

Wild pig depredation on certain forest tree seedlings has been a concern of foresters in the South and West. Wild pigs have destroyed fragile plant communities in Great Smoky Mountains National Park and other preserves. They have been known to damage fences when going into gardens and can do considerable damage to a lawn or golf course in a single night.

In California, wild pigs have entered turkey pens, damaging feeders, eating the turkey feed, and allowing birds to escape through damaged fences. Wild pigs in New South Wales, Australia, reportedly killed and ate lambs on lambing grounds. Producers in Texas and California reported to USDA-APHIS-ADC that 1,473 sheep, goats, and exotic game animals were killed by wild pigs in 1991. Predation usually occurs on lambing or calving grounds, and some hogs become highly efficient predators. Depredation to calves and lambs can be difficult to identify because these small animals may be killed and completely consumed, leaving little or no evidence to determine whether they were killed or died of other causes and then were eaten. Determining predation by wild hogs is possible if carcasses are not entirely eaten, because feral hogs follow a characteristic feeding pattern on lamb.

Always be aware of the potential for disease transmission when feral hogs are associated with domestic livestock. Cholera, swine brucellosis, trichinosis, bovine tuberculosis, foot and mouth disease, African swine fever, and pseudo-rabies are all diseases that may be transmitted to livestock. Bovine tuberculosis was transmitted to beef cattle by wild hogs on the Hearst Ranch in California in 1965. Pork that was infected with hog cholera brought into Kosrae Island in the East Carolinas resulted in the decimation of all domestic and feral hogs on the island.

Economics of Damage and Control
In most areas it is unlikely that wild pigs can be exterminated. It is theoretically possible, but the cost to do so is usually prohibitive. Landowners must generally accept the fact that they will always have some wild pigs and should therefore plan for a long-term control program.

Feral hog damage can be extensive and costly if not controlled. Control for disease suppression is extremely expensive because many hogs need to be eliminated. Crop depredations may cease after one or two hogs are shot or trapped, or intermittent hunting pressure is put on them. They simply move to new areas. If depredations are heavy enough to require a reduction in the overall population then a program can be very costly, depending on the size of the area involved.

Legal Status
Wild pigs are game mammals in California, Texas, Tennessee, North Carolina, Puerto Rico, Hawaii, and Florida. In California, a depredation permit is required from the Department of Fish and Game to conduct a control program or to take depredating animals. Contact your state wildlife agency to determine if a permit is required.


Damage Prevention and Control Methods

Exclusion
Heavy-mesh wire fences and electric fences may be effective, especially around gardens and other small areas.

Frightening
No methods are effective.

Repellents
None are registered.

Toxicants
None are registered.

Trapping
Stationary corral trap. Portable drop gate trap. Leg snare.

Shooting
Sport hunting, especially with dogs, can reduce pig populations in local areas.




ACKNOWLEDGEMENTS
The above information was adapted from PREVENTION AND CONTROL OF WILDLIFE DAMAGE with permission of the editors, Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson (Cooperative Extension Division, Institute of Agriculture and Natural Resources University of Nebraska-Lincoln, United States Department of Agriculture Animal and Plant Health Inspection Service, Animal Damage Control, Great Plains Agricultural Council Wildlife Committee).