Sus cebifrons [Heude, 1888].

Citation: Mem. Hist. Nat. Emp. Chin., 2, pl. 17, fig. 5.

Type locality: Philippines, Cebu Island.

The taxonomic record (above) is taken from Wilson and Reeder (1993). Wild pig taxonomy has changed significantly in recent years: only in 1993 did Sus cebifrons become widely recognized as a separate species. Prior to this, the Visayan warty pig was considered by various authors to be a subspecies of the Sulawesi warty pig (i.e. Sus celebensis negrinus), Philippine warty pig (Sus philippensis cebifrons), or the bearded pig (Sus barbatus cebifrons) (see Groves, 1997; Oliver, 2008). Given its history of being included within other pig species, it is perhaps surprising that recent molecular research indicates that this species is possibly the most genetically distinct member of genus Sus (Oliver, 2004b)

Some authors consider the Visayan warty pig to be monotypic (Groves and Grubb, 1993), while other recognize two subspecies based on islands of origin: S. c. cebifrons, now extinct from Cebu, and S. c. negrinus from Negros (Groves, 1997). A third subspecies from Panay may exist, but the required studies on body and skull morphology have not yet been conducted (Oliver, 2004a; Oliver, 2008). S. negrinus is a synonym for S. cebifrons (Wilson and Reeder, 1993).

Like many island species, the Visayan warty pig is relatively small in size (Oliver et al., 1993). Males are much larger than females, with up to a four-fold difference in body weights between the sexes (Rabor, 1977; Lastica, 2003). These pigs are usually lean, but can become obese in captivity (Lastica, 2006).

S. cebifrons is dark grey or black in overall color (Groves, 1997; Lastica, 2003). Sparse bristly hairs cover most of the body - in females and young males these are predominantly black in color, while in adult males there is often a predominance of silver- or fawn-colored bristles (Rabor, 1977; Groves, 1997; Lastica, 2003). Skins of adult males from Negros exhibit a predominance of white hair on the shoulders and sides (Groves and Grubb, 1993). A tuft of hair is usually present on the crown of the head; this tends to be either dark reddish-brown or black with scattered red or straw-colored hairs (Groves, 1997). In males (and females to a lesser extent) from Panay, this tuft is expanded into a long mane which extends from the forehead down the back to the rump (Groves and Grubb, 1993). This mane is grown and shed annually, and is one of the most distinctive characters of this species, often flopping over the face of the boar and obscuring the eyes.

The body shape is typical of pigs, being barrel-like in form with relatively short legs. Females possess three pairs of mammary glands (also present, but not functional, in males). Other native and domestic Filipino pigs - as well as hybrids between these species and S. cebifrons - possess at least four pairs, providing an important key in the identification of purebred Visayan warty pigs (Lastica, 2003).

The high-crowned skull is relatively small in both sexes, and sexual dimorphism is highly evident in skull morphology (Groves, 1997). Groves and Grubb (1993) provide a few cranial measurements. Externally, the head is elongated with a terminal nasal disc. The ears are small and upright, with slightly pointed tips (Lastica, 2003). Despite being named a "warty pig", the facial warts of S. cebifrons are typically small; males from Panay have the largest warts (Groves and Grubb, 1993; Groves, 1997). Visayan warty pigs never grow gonial warts (on the angle of the jaw) - this spot is marked in males by a wide white tuft of hair; in females, there is usually no tuft and only a small white spot present (Groves and Grubb, 1993; Groves, 1997). Male Visayan warty pigs possess large canines which protrude from the mouth as tusks (Lastica, 2003).

In both sexes, the face is marked with a conspicuous whitish stripe which crosses the bridge of the nose just behind the mouth and follows the jawline to the angle of the jaw (Groves, 1997; Lastica, 2003). This band is generally less obvious in females than males, but is one of the primary distinguishing characteristics for distinguishing S. cebifrons from other Philippine wild pigs (Lastica, 2003).

The gestation period for S. cebifrons is approximately 118 days (Oliver, 1996 in Lastica, 2003). One or two weeks prior to giving birth, females begin showing nesting behavior and may become aggressive to conspecifics (Oliver et al., 1993). Females usually give birth overnight, and are very protective of their offspring (Lastica, 2003). Reports from native hunters indicate that the average number of piglets per litter in the wild is three or four (Oliver et al., 1993), while Lastica (2003) suggests average litter size is two or three. These figures are corroborated by captive births: six of ten North American captive-born litters contained three offspring, with half of the remaining four litters contained two and four offspring each (ISIS, 2005). A record number of five offspring in a litter was observed in two Philippine breeding centers in 2005, although the piglets had to be weaned earlier than usual to help the female regain condition (Lastica, 2007). In the wild, piglets are usually observed during the region's dry season from January to March (Oliver et al., 1993).

Young Visayan warty pigs are marked with thick stripes which run from the shoulders to the rump, alternating between orange-brown and black (Groves, 1997; Lastica, 2003). There are typically four black stripes; one pair runs down the back on either side of a lighter dorsal line, with another stripe running along the flanks and haunches on both sides (Groves, 1997). The striping of the juvenile coat loses definition at seven to nine months of age and adult coloration is fully achieved after one year (Rabor, 1977; Lastica, 2003). Youngsters begin testing solid food at one week of age, and may be weaned by six months (Lastica, 2003). Females are capable of producing a litter every 8 to 12 months (ISIS, 2005).

Females reach sexual maturity at two or three years of age, although captive individuals have conceived at 12 months of age (Lastica, 2003; Zabala, 2010). Males may be capable of siring offspring at 14 months, but the characteristics of adult males do not develop until after two years (Lastica, 2003; Zabala, 2010). In the wild, Visayan warty pigs are believed to live up to 10-15 years (Lastica, 2003).

Knowledge of the Visayan warty pig from the wild is very scarce, due to the rarity of this species, the scarcity of natural habitat, and the challenges involved with observing these animals in the wild. This species was once found in a wide variety of habitats, ranging from lowland and highland grasslands as well as primary and secondary forest (Rabor, 1977). This species is now restricted to densely forested areas on just two islands in the Philippines (Rabor, 1977).

This species is sociable, living in groups of three to over a dozen animals. The composition of these groups is typically a single adult male with several females (usually three or four, as indicated by local hunters), plus young individuals of both sexes (Rabor, 1977; Oliver et al., 1993). Solitary males have also been reported, but are encountered only rarely (Oliver et al., 1993).

In captivity, S. cebifrons will use mud wallows (Lastica, 2003). While pigs are generally not excellent jumpers, one juvenile female on Negros was observed clearing a meter-high fence during a capture attempt (Lastica, 2003).

S. cebifrons, like most pig species, is omnivorous (Lastica, 2003). As determined though indirect observations of tracks and scat, Visayan warty pigs appear to feed on plant species such as Lithocarpus (Fagaceae), Platea excelsa (Icainaceae), and Dillenia reifferscheidia (Dilleniaceae) (Hamann and Curio, 1999). These authors suggest that Lithocarpus and Dillenia may depend solely on S. cebifrons for seed dispersal. Other plant species identified in the diet by Cummings (2003, in Lastica, 2003) include "Gabe gabe" and "Silan" (Colocasia sp. - a favorite of this species), "Lintakuban" (a fruiting tree), "Kagay" vine, "Tugis" palms, wild bananas, avocado, "Batwan", "Lumboy lumboy", and casava. Earthworms ("Duduloy") are frequently consumed (Cummings, 2003, in Lastica, 2003).

S. cebifrons is endemic to the Negros-Panay faunal region of the Philippines, with a range encompassing the Visayan Islands of Cebu (where it is now extinct, the last reports being in the 1960s), Negros, Panay, and Guimaras (now extinct) (Groves and Grubb, 1993; Oliver, 2008). This species may also be present on the island of Masbate (a few animals were present in 1993, but it is not known if the population still survives), and may once have lived on Siquijor and Bohol (where it is now believed to be extinct) (Oliver, 1995; Oliver, 2008).

Countries: Philippines (Oliver, 2008).

The Visayan warty pig has been listed as critically endangered (Criteria A4cde) by the IUCN (Oliver, 2008), but is not listed by CITES (2009). It is one of the most endangered species of wild pig, being extinct in over 95% of its former range and now found only in small, fragmented populations (Oliver, 2004a; Oliver, 2004b). There have been no recent published estimates of population numbers surviving in the wild.

While small isolated populations face numerous problems sustaining their numbers, in the case of the Visayan warty pig there are far more pressing concerns. Human impacts - including habitat destruction, persecution (a result of crop raiding), and intensive hunting for meat - continue to reduce both absolute numbers of Visayan warty pigs and their potential to maintain (never mind expand) their numbers by reducing available resources (Oliver, 2004b; Oliver, 2008). Domestic pigs pose a significant threat to this species, hybridizing with wild warty pigs as well as introducing diseases and parasites. Visayan warty pigs killed by poachers now show (with increasing frequency) obvious hybrid characters, including large ears, reduced manes, and even piebald markings (Oliver, 2004a). Three rescue and breeding centers for this species have been created within the Philippines, and an international breeding program is underway, with captive stock in both North America and Europe (Oliver, 2004a; Oliver 2004b).

Sus is Latin, meaning a pig. The species name cebifrons is likely a combination of Cebu (the island on which the type specimen was collected), and the Latin word frons, meaning the forehead or brow, a reference to the long mane and forehead tuft. Although now extinct on the island of Cebu, S. cebifrons is sometimes called the Cebu bearded pig as a result of the provenance of the type specimen.

Local names

Baboy ilahas [on Visayas; literally "wild pig"] (Rabor, 1977; Lastica, 2003; Lastica, 2007)

Baboy do mor [Local Philippine dialect] (Oliver, 2004a)

Baboy talunon [on Negros] (Lastica, 2003)

Manggalisak banban [half-grown male in Bisayan] (Rabor, 1977)

Biggal [sow in Bisayan] (Rabor, 1977)

Bakatin [small pig in Bisayan] (Rabor, 1977)