Sus philippensis was formally recognized as a distinct species in 1991, after originally having been considered a subspecies of the Sulawesi Pig S. celebensis and the Bearded Pig Sus barbatus. Initially, three subspecies were proposed: S.p.philippensis from Luzon and associated islands; S.p.mindanensis from Mindanao and associated islands, and S.p.oliveri from Mindoro. The latter species was later assigned to full species level. Recent mtDNA studies have suggested that S.p.philippensis and S.p.mindanensis are distinct enough to be considered as full species.

• Sus philippensis philippensis Nehring, 1886 – Luzon

• Sus philippensis mindanensis Forsyth Major, 1897 – Mindanao

S. philippensis is endemic to the Philippines, and occurs through most of the country except the Palawan Faunal Region (where it is replaced by S. ahoenobarbus), Mindoro (S. oliveri), the Negros-Panay Faunal Region (S. cebifrons), and the Sulu Faunal Region (where it is apparently replaced by a closely related, but as yet undescribed species of pig). S. p. philippensis is confined to the ‘Greater Luzon Faunal Region’ (i.e. the islands of Luzon, Polillo, Catanduanes and, formerly, Marinduque). S. p. mindanensis is confined to the ‘Greater Mindanao Faunal Region’ (i.e. Samar, Leyte, Biliran, Bohol, Mindanao, Camiguin Sul, Basilan and associated smaller islands.

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Precise data on wild pig populations is lacking for most of these islands, particularly the smaller ones. The present status of S. philippensis may be inferred from the extent of remaining forest over their known ranges, likely extents of hunting pressure and other factors. As such, the species was undoubtedly far more extensively distributed in the past, and most extant populations, particularly on the larger islands, are badly fragmented and declining.

This is a species of Sus with karyotype 2n = 36, unlike other wild species, as well as domestic pigs, in which 37 or 38 chromosomes is more common. S. philippensis is generally black with grey skin, sometimes with a pale snout-band and red-brown patches in the mane. They have a long, full crown tuft and nuchal mane, which extends along the back in most individuals, especially adult males. Males have 2 pairs of warts, and gonial hair tufts that are very long and thick, and largely white or yellow. Adult sows also have distinctive white, but much thinner, gonial tufts.

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The skull has deep, sharply bordered preorbital fossa. Compared to S. celebensis and S. scrofa, the facial skeleton is somewhat elongated but not as much as in S. barbatus or S. verrucosus. The face is somewhat concave at the nasal root, with nasals slightly convex and the malar tuberosity greatly swollen. The braincase is high-crowned, sloping downward to facial skeleton, and with the occipital crest extending backward. The anterior margin of the temporal fossa is perpendicularly above M3 or just behind it. The foramen magnum is described as "teardrop-shaped". The maxillary premolar rows curve outward anteriorly. M3 is very short, with four major cusps and a small 5th cusp.

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The two subspecies are morphologically distinct. S. p. philippensis is a subspecies with a greyish crown tuft, with an anterior fringe that is directed forward. The facial warts are relatively large, and the gonial whorls white. The skull size in males is relatively small, and the braincase is shortened and relatively flat-topped. S. p. mindanensis closely resembles S. p. philippensis, but differs in the following features: the crest and mane are mostly black, but often distinctly intermixed mixed with white or reddish-brown hairs, though the crown tuft may be white anteriorly; but the forwardly-directed fringe is seemingly absent or less apparent in most individuals. The facial warts are small, though the gonial tufts, usually yellow or yellow mixed with black, are prominent, if much more developed in adult males than females. Skull size of S. p. mindanensis is also much larger in males than females, and the braincase more rounded in comparison to S. p. philippensis.

S. philippensis was formerly abundant from sea-level up to at least 2,800 m, in virtually all habitats, but now it is common only in remote forests. It was recently reported to be common in montane and mossy forest from 925–2,150 m elevation in Balbalasang National Park, Kalinga Province in Luzon, and a recent birding trip report found many pig wallows in the park. In the Kitanglad Range on Mindanao, signs of pigs were also seen in montane, mossy forest between 1800 and 2000 m. In 1996, a specimen had been found at 1100 m, and in 1960 at ca. 1300 m, but it is unclear whether the species still survives at these altitudes today in Kitanglad. Habitat information from other areas is scarce, but it is assumed that the species is now largely restricted to higher altitude forests in remoter areas.

Nothing is known specifically about what the species feeds on in high altitude forests, but presumable it survives on a diet of tubers, fallen fruit, and invertebrates.

Little is known of the species' circadian activity in remoter areas, but it is reported to be essentially nocturnal in areas subject to human disturbance. 

Nothing is known.

Little is known. The species has seldom been bred in captivity, though a litter of 5 piglets has been reported on one occasion.

S. philippensis is listed in the IUCN Red list as Vulnerable because it is currently undergoing a drastic population decline, estimated to be more than 30% over a period of three generations (estimated to be about 21 years), inferred from the apparent disappearance of several populations, and the effects of over-hunting, habitat loss and hybridization.

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The species' habitat is threatened by continued low-level illegal logging and agricultural expansion. Pig hunting continues throughout remaining range of S. philippensis, including many (perhaps most) protected areas. Hunting is mostly practiced by local farmers and indigenous peoples in hinterland communities and recreational hunters from larger cities. Both of these groups also sell any surplus meat which usually commands at least twice the price of domestic pork in local markets and speciality restaurants. Efforts to reduce or discourage hunting are often compromised by generally negative attitudes towards these animals, which can cause severe damage to crops planted within or close to existing forest boundaries, and which are therefore regarded as pests. Unfortunately, this species is also threatened by genetic contamination via hybridization with free-ranging domestic and feral animals of ex-S. scrofa origin, and incidences of such hybridizations have been confirmed from Luzon and Mindanao, and reported from Basilan and other islands.

Text adapted from: Meijaard, E., J. P. d'Huart, and W. L. R. Oliver. 2011. Family Suidae (Pigs). Pages 248-291 in D. E. Wilson, and R. A. Mittermeier, editors. Handbook of the Mammals of the World. Vol 2. Hoofed Mammals. Lynx Edicions, Barcelona, Spain.

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