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EN - Javan Warty Pig

Javan Warty Pig (Sus verrucosus)
Status: Endangered A2cd ver 3.1
Pop. trend: decreasing


Photo by Herman Rijksen
Taxonomy
. Sus verrucosus Müller, 1840, Java.

The ancestry of this species has been traced back to some fossil pig species of Java, which combined with phylogenetic data suggest that the species has evolved on Java for ca. 2 million years.

Subspecies and Distribution (see map).

S. v. verrucosus Müller, 1840 West and Central Java. Extinct on Madura Island

S. v. blouchi Groves, 1981 Bawean Island

The Javan warty pig Sus verrucosus is endemic to the islands of Java, Madura and Bawean in Indonesia. It occurs alongside S. scrofa vittatus, but it appears that the two species avoid each other and attain their highest densities where the other species is absent. S. verrucosus was widespread on Java as recently as 1982, but is now absent from most of the island, and is surviving only in highly fragmented populations.

The Cikananga Wildlife Center runs the only really successful captive breeding and conservation program for the Javan Warty Pig. The photo on the below shows one of the Cikananga Warty Pigs residing in a semi natural enclosure.

A Java-wide, interview-based survey in 2003 found that there were about 10 areas on Java and Bawean where S. verrucosus populations survived, although other small groups may have existed  elsewhere. These include remnant and low density populations in west Java in the areas between Malingping and Rangkasbitung, and between Sukabumi and the coastal nature reserves of Cikepuh. S. verrucosus is very rare near Purwakarta, while near and south of Garut several small populations remain, with a few reported sightings of S. verrucosus in 2002 and just before. Around Majalengka and towards Sumedang, interviewees reported recent killings of S. verrucosus, but the species is now much rarer than in the past. A population of S. verrucosus still exists East of Tasikmalaya towards Ciamis, although people consider S. verrucosus to be rare in comparison to S. scrofa. Several interviewees reported recent sightings of S. verrucosus from the area around Cilacap, Cipatujuh, and Nusa Kembangan NR, including some from the Nusa Kembangan Nature Reserve offshore Cilacap, but the species seems to be rare and fragmented into small populations. The only areas where S. verrucosus reportedly remained common were around Subah, where animals were generally seen in small groups of 1–2 animals, but 4–6 animals/group during mating season, and around Blora and Bojonegoro. In the latter area, group size had reportedly declined from 10–20 animals to only 1–3 animals/group.

No recent records of S. verrucosus exist from Madura Island, and the species is considered extinct on the island.

On Bawean Island, the only area where the subspecies S. v. blouchi occurs, the species is now very rare, and possibly already extinct or functionally extinct. There is a proposal to elevate the Bawean Pig to species level, Sus blouchi, which would make this likely the most endangered wild pig species in the world.

Descriptive notes. Head-body 90–190 cm, shoulder height 70–90 cm, weight 35–150 kg. Compared to other species of Sus the Javan Warty Pig is characterized by the great elongation of the face, and more pronounced sexual dimorphism. The male S. verrucosus is easily distinguished from other species (at least when seen from nearby) by the presence of warts. Observations from 2 captive S. verrucosus indicates that warts start to grow at 17 months old at approximately 25–35 kg.

The two pig species on Java are externally quite similar, and it will often be difficult to determine the species when an animal is seen running anyway in the distance, or when it is a female (which lacks the warts). Compared to S. scrofa, S. verrucosus gives the impression of having a very large, heavy head, at least in adult males. Males of S. verrucosus are much larger than females (ca. 90 kg for males as opposed to 45 kg for females). Such pronounced sexual dimorphism is not found in scrofa, where the males weigh about the same as the verrucosus males, but the females are much heavier.

Pelage colouration varies greatly in both species. Generally verrucosus appears somewhat reddish, but some individuals look quite black from a distance. The hair on the crown and the mane on the back of the neck are usually a lighter hue, often reddish-orange and occasionally approaching blond. In verrucosus of all sexes and ages the hair on the belly is predominantly white or yellowish, contrasting with the darker pelage on the upper part of the body. S. scrofa on Java are most often black or grizzled, but reddish-brown ones are sometimes encountered. The mane is usually black and belly hairs are also dark, not contrasting with the pelage above. The individual hairs in S. scrofa are of a single type: black with a band or (when worn) tip of yellowish. In S. verrucosus there are two hair types intermixed: shorter red or yellow hairs with black tips, and longer black ones.

The coloration of piglets in the two Javan pig species differs as well. S. scrofa piglets are longitudinally striped, black-brown and whitish to fawn; the striping is very conspicuous. In verrucosus, on the other hand, the striping of piglets is very faint and may be difficult to discern in the field.

The shape of the lower canines in male pigs is another good indicator of their specific identity. If a cross section is take near the base, in S. scrofa the inferior surface is the narrowest of the three, while in S. verrucosus it is as broad as the enamel-less posterior surface. If the width of inferior surface is expressed as a percentage of the posterior surface, then for scrofa this ranges between 61.5 and 109.1 %, and for verrucosus it ranges between 113.3 and 161.5 %.

The canines in females are also distinctive. In S. scrofa they are fairly large: the greatest diameter of the upper canine varies between 16.8 and 18.2 mm, of the lower between 14.0 and 17.0 mm, overlapping the male range. In S. verrucosus the canines of females are much smaller, the upper measuring 9.3–11. 5 mm, the lower 7.3–10.0 mm.

The race blouchi is distinguished from the nominate subspecies by it smaller size, the relatively low occiput, the red color of the pale hairs in the coat, and the red mane.

Habitat. S. verrucosus occurs both in cultivated landscapes and in teak (Tectona grandis) forest plantations, interspersed with lalang grasslands (Imperata cylindrical), brush, and patches of secondary forest. S. verrucosus are everywhere restricted to elevations below about 800 m. The reasons for this are not known, but it might be due to their being unable to tolerate low temperatures. They evidently prefer secondary or disturbed forests, though they are also often found near the coasts in remnant patches of mangrove and swamp forest. They are rare in the few remaining lowland primary forests, and in areas with high human populations where otherwise suitable habitat is fragmented and surrounded by agricultural land. However, they do feed on crops, making nocturnal raids on fields of corn and cassava and, in common with Sus scrofa, the species is widely persecuted for such depredations. The two species appear to avoid each other. In the 1920s, their abundance was thought to be similar, but only one species was generally found in one particular location. Sus scrofa appeared to be the better adapted species to agricultural areas and heavily degraded forests, with S. verrucosus being more restricted to woodlands.

Food and Feeding. Ecological information about S. verrucosus is rare because at a time when the species was still relatively common, extensive descriptions of feeding and breeding ecology did not differentiate between S. verrucosus and S. scrofa. One ecological account from 1928 describes the ecological similarities between the two species. Both species feed on a range of animal and plant foods, including fallen fruits, roots, worms and insects. They are particularly partial to ripe rice, making them a feared agricultural pest.

Activity patterns. There is little known about activity patterns of S. verrucosus. Interview surveys on Java in 2003 suggest that the species is mostly nocturnal, with several respondents reporting that crop damage to rice fields almost exclusively happened at night. It could be that a shift from generally diurnal activity patterns in pigs to nocturnal ones is because of the very high hunting pressure on the species.

Movements, Home range and Social organization. No estimates of home range or population density are available. Historically, group sizes of up to 20 animals were reported, though most  recent records refer to groups of no more than 6 individuals during the breeding season and fewer at other times.

Breeding. The gestation period is thought to be about 4 months, and 3–9 young are born. Most births reportedly occur in the rainy season from January to March, in a large nest made by the female out of leaf litter, and according to a recent informant, females with young are mostly seen between August and December.

Status and Conservation. The species is listed as Endangered on The IUCN Red List. The species is now restricted to several isolated areas on mainland Java. There are no estimates of overall population size, but the species has shown a rapid population decline in recent decades. Compared to a survey conducted in 1982, 17 of the 32 (53%) populations are extinct or have dropped to low encounter rate levels.

It is thought that the population decline observed in this species is primarily caused by a decline in suitable habitat, especially of stands of teak Tectona grandis forest or similar forest plantations, and by high hunting pressure. These animals are killed both by sport hunters and by farmers protecting their crops. Many animals are killed by poisoning.

As yet unpublished reports of the recent dramatic reduction in numbers, possibly resulting in the extirpation, of S. v. blouchi, on Bawean Island have been attributed to correspondingly increased hunting pressure following the recent settlement of Christian immigrants from Sumatra; these animals having been previously left largely unharmed by the predominantly Muslim inhabitants.

Competition from and hybridization with the Eurasian wild pig, Sus scrofa has been speculated as a further threat to S. verrucosus, especially in areas where human induced habitat changes favor S. scrofa.



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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