Around half of the 18 or so species in the pig family (Suidae) are in the genus Sus. By far the best known and widely distributed pig is the Eurasian Wild Pig or Wild Boar (Sus scrofa). Indeed, this species has one of the largest geographic ranges of any mammal. The enormous geographic variation in appearance--amplified by the intentional and accidental release of wild, domesticated, and hybrid forms across various parts of the range--led to the description of a large number of putative species and subspecies now widely viewed as invalid (although new data and analysis may yet result in the revival of some of these names).
Before human intervention, this species was present from the British Isles in the extreme west through Eurasia from southern Scandinavia to southern Siberia and extending as far east as Korea and Japan and southeast to some of the Sunda Islands and Taiwan. To the south, this species ranged along the Nile valley to Khartoum and north of the Sahara in Africa and roughly followed the continental coasts of south, east, and southeast Asia. Within this range, it was absent only from extremely dry deserts, such as the driest regions of Mongolia, and alpine zones such as the high altitudes of the Pamir Mountains.
In recent centuries, humans have had a dramatic impact on the distribution of the Eurasian Wild Pig through hunting and habitat modification. The Eurasian Wild Pig disappeared from the British Isles in the 17th century and from Denmark in the 19th century and during the 20th century its numbers and distribution declined over much of its range in locations as far-flung as Tunisia, Sudan, Germany, and Russia. In the mid-20th century, there were moderate population recoveries following these severe declines in Russia, Italy, Spain, and Germany and both natural and assisted range expansions in Denmark and Sweden. The species has also been accidentally reintroduced to Great Britain via escapes of mixed-origin pigs from commercial farming operations. Introduced feral populations derived from this species are serious pests causing severe ecological disruption in many parts of the world including Australia, New Zealand, the eastern Malay Archipelago, North America, Central America, and South America, among others.
The Eurasian Wild Pig is ecologically flexible and may be found in habitats ranging from closed natural and planted forests to open scrublands with some cover. In Europe, they are found in agricultural landscapes as well as riverine and mountainous forests, reaching especially high densities in oak-dominated forests. In Southeast Asia, this species may be found in mature forests, secondary forests, gardens, and plantations. It can reach very high densities in dipterocarp forests during periods of mast-fruiting. Although these wild pigs generally avoid open agricultural fields, when crops are taller they may enter fields and cause considerable damage.
The diet of the Eurasian Wild Pig is extremely varied and can even include young deer and lambs. The pigs themselves may be preyed upon by Gray Wolves, Dholes, Tigers, Leopards, Eurasian Lynxes, and large reptiles such as crocodiles and pythons.
The gestation period is around 112 to 130 days. Litter size is typically between five and nine young, each piglet weighing 750 to 1000 g at birth. The piglets begin to eat solid food, such as worms and grubs, at about 2 weeks and are weaned at 3 to 4 months. Eurasian Wild Pigs may live over 20 years in the wild. Adults are dangerous when they feel threatened. A male will lower its head, charge, and slash upward with his tusks; a female, whose tusks are not visible, will charge with her head up, mouth open, and bite. Eurasian Wild Pigs tend to be most active between dusk and dawn.
Although this species is secure globally, many local populations are vulnerable due to hunting pressure as well as hybridization with domestic and feral pigs.
There are an estimated 2 billion domesticated pigs on our planet, which are derived mainly from Eurasian Wild Pigs and Sulawesi Warty Pigs (Sus celebensis). There is evidence that local pigs were domesticated independently in Europe, Asia Minor, the Far East (including Japan), and various parts of Southeast Asia. The earliest evidence of domestication dates back more than 10,000 years.
(Meijaard et al. 2011 and references therein)