Description and behaviour
A typical pig has a large head with a long snout which is strengthened by a special prenasal bone and by a disk of cartilage at the tip. The snout is used to dig into the soil to find food and is a very acute sense organ. There are four hoofed toes on each trotter (foot), with the two larger central toes bearing most of the weight, but the outer two also being used in soft ground.
The dental formula of adult pigs is
, giving a total of 44 teeth. The rear teeth are adapted for crushing. In the male the canine teeth form tusks, which grow continuously and are sharpened by constantly being ground against each other.
Distribution and evolution
With around 1 billion individuals alive at any time, the domesticated pig is one of the most numerous large mammals on the planet.
The ancestor of the domesticated pig is the wild boar, which is one of the most numerous and widespread large mammals. Its many subspecies are native to all but the harshest climates of continental Eurasia and its islands and Africa as well, from Ireland and India to Japan and north to Siberia. Although it has been exterminated in some areas, its numbers are stable, or even increasing rapidly, in most of its native range.
Long isolated from other pigs on the many islands of Indonesia, Malaysia, and the Philippines, pigs have evolved into many different species, including wild boar, bearded pigs, and warty pigs. Humans have introduced pigs into Australia, North and South America, and numerous islands, either accidentally as escaped domestic pigs which have gone feral, or as wild boar. These have typically adapted well, and are increasing in number and broadening their range outside human control.
Habitat and reproduction
The wild pig (Sus scrofa) can take advantage of any forage resources. Therefore, it can live in virtually any productive habitat that can provide enough water to sustain large mammals such as pigs. If there is increased foraging of wild pigs in certain areas, it can cause a nutritional shortage which can cause the pig population to decrease. If the nutritional state returns to normal, the pig population will most likely rise due to the pigs' naturally increased reproduction rate.
Diet and foraging
Pigs are omnivores, which means that they consume both plants and animals. In the wild, they are