Visayan warty pig
ssp. cebifrons (now extinct) and negrinus (islands of Negros & Panay, Philippines)
Status: Critically Endangered
Did you know? Visayan warty pigs are typically characterised by a mane which often flops over their face, obscuring their eyes, and extending back to their loins.
This species was only upgraded to full species level in 1993, having previously been considered a subspecies of respectively S. celebensis, S. philippensis, and S. barbatus. However, two recent independent phylogenetic studies suggest that S. cebifrons is actually very distinct from these previous three species and perhaps the most primitive member of the genus Sus. Genetic analysis indicates that a split occurred very early in the genus' evolution separating the Philippine species from all others. Recent divergence estimates suggest that this happened some time during the very late Pliocene or early to middle Pleistocene.
Two subspecies are currently recognized, i.e. the nominate form from Cebu (now extinct) and negrinus from Negros. Recent MtDNA studies have indicated the likely addition of a third subspecies from Panay; whilst a fourth population from the remoter island of Masbate is still known only from a single specimen that is yet to be formally described or compared to other populations.
Subspecies and distribution
Sus c. cebifrons Heude, 1888 – Cebu Island, Philippines.
Sus c. negrinus Sandborn, 1952 – Negros Island, Philippines
S. cebifrons is endemic to the West Visayan Islands (or Negros-Panay Faunal Region) of the central Philippines, where it is known or presumed to have occurred on all of six main islands of Cebu (extinct; the last reports being in the 1960s), Negros, Guimaras (extinct), Panay, Masbate and Ticao (extinct). It is not known whether S. cebifrons or S. philippensis occurred formerly on the neighboring island of Siquijor, where wild pigs have also been extirpated, but this species is replaced by S. philippensis on Bohol and all other larger Philippine Islands east of Huxley’s Line, except on Mindoro where it is replaced by S. oliveri. This species has been extirpated from most of its range, and fragmented populations survive today only on the islands of Negros and Panay. The species may still occur on Masbate Island, although no confirmed reports have been made since 1993.
S. cebifrons is relatively small in size compared to other pig species. Head-body length is about 100 cm, shoulder height is 30–45 cm in females and up to 63 cm in males, tail length is 23 cm, adult weight 20–35 kg in females and 35–40 kg in males, although weights of up to 80 kg have been reported from Negros. Males are much larger than females, with up to a four-fold difference in body weights between the sexes.
The coat is generally grey-black in females and sub-adult males, but more fawn mixed with black in adult males. Both sexes have distinct manes extending from crest to the hindquarters. Males in breeding condition develop even longer manes that are grown and shed annually, i.e. at the beginning and end of each breeding season (usually November to late March/early April). The mane is a very distinctive character of this species, often flopping over the face of the boar and obscuring the eyes, and extending back to the loins. Females have a weakly marked snout band, but this is very broad and well-marked white or whitish yellow in males. The snout band is a very useful external characteristics to distinguish S. cebifrons from other Philippine pig species. Despite its common name Visayan Warty Pig, the facial warts of S. cebifrons are typically small, and completely lack gonial warts (on the angle of the jaw).
The young of S. cebifrons are marked with thick stripes which run from the shoulders to the rump, alternating between orange-brown and black. 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. The striping of the juvenile coat loses definition at seven to nine months of age and adult coloration is fully achieved after one year.
This species is thought to have been extirpated over at least 98% percent of its presumed former range, including at least three of the six main island in the West Visayan group. Originally this species occurred in primary and secondary forest from sea-level to mossy forest at 1,600 m asl, but the disproportional loss of lower altitude forests have now confined and isolated to the few last remaining, still-forested habitats above 800 m asl. Small numbers of these animals are also known to persists in some degraded habitats such as Imperata cylindrica grasslands as long as there are areas of dense cover; though there is evidence that some or most of these are probably either feral domestic pigs and/or hybrids between this species and free-ranging domesticates of (ex-) S. scrofa origin. In captivity, S. cebifrons readily bathe in open pools and use mud wallows, and it is assumed that these animals also do this in the wild state.
S. cebifrons is omnivorous, feeding on a range of plant and animal species. Because of the species' scarcity in the wild there are no direct reports of feeding behavior, but some information has been obtained from scats and feeding signs. The species appears to feed on plant species such as Lithocarpus (Fagaceae), Platea excelsa (Icainaceae), and Dillenia reifferscheidia (Dilleniaceae), with the former two species possibly being completely dependent on S. cebifrons for the dispersal of their seeds. The species also appears to feed on a range of vines, palms, wild bananas, and agricultural crops such as taro and avocados, as well as earthworms. Captive animals will readily consume a wide variety of cereals, fruits, vegetables, leafy branches, grass; and most individuals will avidly consume any rodents (rats and mice) and other ‘prey’ items.
Little has been reported about the activity patterns of S. cebifrons in undisturbed areas, since any such are likely to be so remote and the terrain so rugged as to make even chance observations unlikely. Conversely, in the wider majority of areas where the species is heavily hunted, it avoids human activity (but may ‘raid’ agricultural crops planted within or close to forest edges) and is mainly active at night. Camera trapping of the species could reveal a lot more about its activity patterns but such activities have only recently been started (see here).
Movements, home range and social organisation
This species is sociable, mostly living in small groups (though up to a dozen individuals have been reported), but considering its much reduced densities larger groupings would likely form under more natural conditions. Animals in zoos are described as "playful and friendly", which may be further reference to their social nature. The composition of S. cebifrons 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. Solitary males have also been reported, but are encountered only rarely. Conversely, captive boars are routinely left with peri-natal sows; the latter vigorously defending their farrowing nests from intruding boars (and caretakers), but generally allowing boars full access to infants within a few days of their first emergence from the nest.
The breeding behavior of S. cebifrons is primarily known from captive populations. The gestation period is about 118 days, and one or two weeks prior to giving birth, females begin showing nesting behavior and may become aggressive to conspecifics. Females usually give birth overnight, and are very protective of their offspring. Litter size in the wild is between two and four, which is similar to those in captivity. A record number of five offspring in a litter was observed in two Philippine breeding centers in 2005. Juvenile animals begin testing solid food at one week of age, and may be weaned by six months. Females are capable of producing a litter every 8 to 12 months. Females reach sexual maturity at an age of two or three years. Males may be sexually mature at two years, but do not possess the fully-developed characteristics of adult males. Captive Visayan warty pigs can live up 18 years.
Status and conservation
The IUCN Red List has categorized S. cebifrons in their highest threat status, Critically Endangered. It is thought to be extinct in over 95% of its former range and now found only in small, fragmented populations. Besides the loss of suitable forest habitat, the species is highly threatened by hunting for food and to reduce crop raiding. Hybridization is another threat with recent evidence suggesting that the species may have bred with domestic pigs. This is obvious in animals killed by poachers which now show (with increasing frequency) such hybrid characters, including shortened snouts, large ears, reduced manes, stockier bodies and even piebald markings.
In response to increasing evidence of its critically threatened conservation status, the IUCN/SSC Pigs, Peccaries and Hippos Specialist Group and other supporting partner agencies (including the Zoological Society of San Diego and, subsequently, the Rotterdam Zoo) devised and initiated a ‘Visayan Warty Pig Conservation Programme’ under the auspices of a new ‘Memorandum of Agreement’ with the Philippine Government’s Department of Environment & Natural Resources (DENR), first signed in 1993. Priority activities identified and implemented under the auspices of this MOA included various follow-up field status and ethnobiological surveys, education/awareness campaigns, development of new protected areas, and the establishment of properly structured conservation breeding programmes. Of these, the latter aspect centred around the development of scientifically managed wildlife rescue and breeding centres on both Negros and Panay Islands, and therefore also involved the development of similar species’ recovery programmes for a variety of other most threatened taxa endemic to the West Visayas (e.g. the Visayan spotted deer Rusa alfredi, and Visayan writhed hornbill Aceros waldeni). This was done partly with a view to possible future reintroductions of these species, but also a means of ‘opportunistically’ acquiring sufficient numbers of founder individuals over time (i.e., not taking any additional animals from the wild state, but instead rescuing live animals illegally caught in snares by local hunters, orchestrating the confiscation of live individuals offered for sale in local meat markets and prevailing upon local owners to donate individuals they had acquired as pets from similar sources). In the case of this species there was also an overriding prerogative of attempting to ensure the survival of pure-bred animals whilst the opportunity still existed to do so. For these same reasons, every attempt was also made to validate the precise origin and likely genetic purity of any such founder individuals in order to also ensure the likely purity of the separate stocks of these animals from and on Negros and Panay (actions since vindicated by the aforementioned new evidence of important genetic differences between these populations). First and second generation captive-bred animals of both Panay and Negros Island origin have also been exported on ‘breeding loan’ from the Philippine Government to San Diego and Rotterdam Zoos (respectively), and now being cooperatively managed in a number of approved breeding centres in the USA and Europe.
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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