Pigs are medium-sized mammals whose thick bodies weigh anywhere from 77 to 770 pounds (35 to 350 kilograms). Some domesticated, tamed, breeds weigh up to 990 pounds (450 kilograms). Pigs measure 34 to 83 inches (86 to 211 centimeters) in length and stand 21 to 43 inches (53 to 109 centimeters) high. The exception is the pygmy hog, which is the smallest species and never grows longer than 28 inches (71 centimeters).
The neck is short and the head is long and pointed. The snout is able to move separately from the head. The eyes are small, the ears are long, and each foot has four toes. The two middle toes are flattened and have hooves. The upper canines, cone-shaped teeth on each side of the front of the mouth, are big and curve upward, protruding from the mouth. Skin color varies, depending on the species, from brown to near black. Some species have manes or tufts of hair. Others have warts on the face.
Pigs live on every continent except Antarctica. They also occupy a number of oceanic islands. They are not indigenous (inDIJ-un-us), native, to all ranges, but have been introduced by humans.
Pigs live in altitudes of up to 13,000 feet (4,000 meters) and choose their habitats depending upon the availability of food, weather conditions, and the predator, animals that hunt pigs for food, population. African pigs occupy small territories or home ranges while other pigs tend to roam in search of better feeding grounds. Regardless of species, pigs build nests out of vegetation for protection from weather as well as for resting. Warthogs do not build their own nests but use those belonging to aardvarks. Home ranges must have sources of shade as well as water and mud holes. These three characteristics are important because some pigs do not have sweat glands to cool their bodies.
Wild pigs are omnivorous, eating meat and plants, feeding on leaves, grasses, seeds, fruits, eggs, young trees, carrion, or dead animals, invertebrates, or animals without backbones, and small vertebrates, animals with backbones. They also enjoy mineral licks where they ingest nutrient-rich soil or water.
BEHAVIOR AND REPRODUCTION
The basic group is the mother-offspring pair, and group sizes vary from one to fifteen pigs. Females live alone or in a group with other females, and offspring remain with their birth group up to two years. Female offspring sometimes remain with the group permanently, but males always leave. With the exception of the African species, males and females interact only during breeding season. African males live with the group year-round and help raise the young. Male warthogs breed, leave, and then return to help care for the offspring.
Pigs vocalize when they are alarmed or in pain as well as when they are comfortable or breeding. Displays are used to ward off intruders or rivals, but if that fails, pigs will fight using tusks. Cannibalism and infanticide, killing of young, have been observed in some species, and wild piglets have been known to be playful and social.
Wild pigs are active at night. Warthogs are active during daylight hours.
Male pigs breed with several females each season, but warthogs have been known to choose one mate for life. Courtship behavior includes chasing and calling. Pregnancy lasts 100 to 175 days, and during this time the female will build a nest from vegetation. Females give birth to one to twelve piglets in this secluded spot. The litters of domesticated pigs increase in number with age and may reach eighteen piglets. Piglets nurse, drink their mother’s milk, up to twenty times each day. Some piglets are taken off mother’s milk as early as five weeks, while others wait until thirty-two weeks of age. Sexual maturity of young is reached at eight months in some species, and at two to five years in others.
Primary predators of wild pigs are bobcats, coyotes, and black bears.
PIGS AND PEOPLE
Wild pigs and humans do not get along well. Wild pigs seriously damage crops by eating them or digging them up by the roots. Humans hunt pigs for their meat and they provide natives in Asia and parts of Africa with income through commercial hunting. Some wild pigs carry disease that threatens domestic livestock. In some cultures, pigs are used in place of money. Domestic pigs are used in scientific and medical research, and their organs have been used as replacements for human organs. Humans have been the recipients of pig hearts, kidneys, livers, lungs, and pancreas (PAN-kree-us) tissue.
The babirusa and the Philippine warty hog are Vulnerable, facing a high risk of extinction in the wild. The Javan pig is Endangered, facing a very high risk of extinction in the wild. The pygmy hog and the Visayan warty pig are Critically Endangered, facing an extremely high risk of extinction in the wild. There is no enough data about the Vietnam warty pig, but it may be extinct, died out.
The main threats to these wild pigs are hunting and loss of habitat. Although some pigs are protected by law from hunting, those laws are not well enforced.