Feral hogs were first introduced to the United States in 1493 on Christopher Columbus's second voyage to the new world. They were brought with other livestock to be used for food, but they soon escaped captivity. These animals were reported to be very aggressive and attacked Spanish soldiers. There numbers now exceed 2 million in the U.S. The effect of the introduced species would later have a detrimental effect on the many different ecosystems they encountered. Since hogs are omnivores, they can have a variety of effects on many different animals from amphibians to mammals. .
Feral pigs eat a variety of items, including fruits, roots, mushrooms, and invertebrates, depending on the season. The major foods in spring are herbage, roots, invertebrates, and vertebrates. Fruit, invertebrates, and herbage are most common in fall and winter diets. Herbage eaten by feral pigs includes water hyssop, pennywort, frog fruit, spadeleaf, onion, and various grasses while important roots used for food include bulrush, cattail, flatsedges, and spikesedges. Fruits and seeds such as grapes, acorns, and cultivated sorghum are important, and animal matter ingested by feral pigs includes earthworms, marsh fly larvae, leopard frogs, snakes, and rodents.
Feral hogs as we know them today are the decendants of European hog, escaped domestic hogs, and the crossbreeds from the two. The only native pigs to the United States is the Collared Peccary in the west. European wild hogs have several distinguishing characteristics that set them apart from domestic or feral hogs. Among these are brown to blackish brown color, with grizzled guard hairs, a mane of hair running dorsally from the neck to the rump, a straight heavily tufted tail, and ears covered with hair. Characteristics of feral hogs are varied, depending upon the breed of the ancestral stock. European wild hogs and feral hogs interbreed readily, with traits of European wild hogs apparently being dominant.