The Pygmy Hog is the smallest and rarest wild suid in the world. The species was historically known from only a few locations in northern West Bengal and north-western Assam in India, though it is now believed likely to have occurred in an extensive area of tall, alluvial grasslands south of the Himalayan foothills from north-western Uttar Pradesh and southern Nepal to Assam, possibly as far as southern Bhutan. After at least two decades without reported sightings the species was already feared extinct. However, in 1971 it was coincidentally ‘rediscovered’ in two separate locations in north-western Assam; namely Barnadi Reserve Forest in Darrang District and Manas National Park. Subsequent field surveys confirmed its continued occurrence in several other reserve forests in north-western Assam in the late 1970s, but continued commercial forestry operations resulted in its extirpation in all of these areas by the early to 1980s and in Barnadi by the late 1980s/early 1990s. Extensive surveys in other parts of its former range during the 1980s and early 1990s also failed to locate any other surviving populations. These findings substantiated growing concerns that the species had been reduced to only a few disparate locations in and around Manas National Park. Successful captive breeding of the species and its reintroduction to the wild has ensured its survival for now.The species nonetheless remains severely threatened throughout its last remaining range even in Manas, through degradation of its habitat through dry-season burnings, risk of disease through increased incursions by domestic livestock and other factors.
Pygmy Hogs measure about 65 cm in length, with a head and body length range of 55–71 cm. Shoulder height is about 25 cm adult animals weigh 6·6–9·7 kg. Females are a little smaller and the newborn babies weigh only 150–200 g. Pygmy Hogs differ from members of the genus Sus in the extreme reduction in body, ears and tail size, relatively short medial false hooves, and snout disc perpendicular to axis of head. There is an absence or warts or gonial whorls, while the body shape is more ‘streamlined’ than in other pigs; in adults tapering from relatively longer hind quarters to smaller forequarters.
Pygmy Hogs prefer undisturbed patches of grassland dominated by early successional riverine communities, typically comprising dense tall grass intermixed with a wide variety of herbs, shrubs and young trees. Grasslands dominated by Narenga porphyrocoma, Saccharum spontaneum, S. bengalensis, Imperata cylindrica and Themeda villosa, forming characteristic grass associations of 2 to 3 m height. Most such communities are subject to wide-scale annual burning and accordingly characterised by a low diversity and a preponderance of a few, fire-resistant grasses, and therefore almost certainly constitute sub-optimal habitats for pygmy hogs. The species is not found in areas subject to prolonged inundations during the monsoon. (e.g., structurally similar grasslands located in riverine floodplains). The generally high soil fertility of these alluvial areas also makes them highly suitable for human settlement and agricultural development; thereby contributing to the rapid decline of these habitats and these animals throughout their known or presumed former range.
Pygmy Hogs feed on roots, tubers, shoots and ground vegetation, along with worms and other invertebrates and, probably, small vertebrates (e.g. reptiles and the eggs and nestlings of ground nesting birds).
Movements, home range and social organisation
Adult male Pygmy Hogs are usually seen by themselves, but are reported to join estrous sows during the rut and to associate loosely at other times of the year with the basic natal social family units. These units usually consist of four to six individuals, including one or more adult females and accompanying juveniles.
Reproduction is strongly seasonal, with almost all births occurring in a single, well defined birth peak, which coincides with the onset of the monsoon (i.e., in late April and May in western Assam). Litter size varies from two to six, but it usually three or four. The species is unusual among the suids in that nests are constructed and used by both sexes at all times of the year and nest building is not, therefore, associated with farrowing only.
Status and conservation
The IUCN has listed Pygmy Hogs as Critically Endangered. It is also listed in the Schedule I of the Indian Wildlife (Protection) Act, 1972. The main threats to survival of Pygmy Hog are loss and degradation of habitat due to human settlements, agricultural encroachments, flood control schemes, and traditional forestry management practices. Some management practices, such as planting of trees in the grasslands and indiscriminate use of fire to create openings and to promote fresh growth of grass, have caused extensive damage to the habitats the authorities intend to protect. In fact, large scale burning of grass in the dry season remains the single most important threat to the continuing survival of these animals, though the reduction and fragmentation of their habitat and other anthrogenic disturbances also bring increased risks of contagious disease via contact with domestic livestock and other factors.
A highly successful conservation breeding programme was initiated in 1996 following the construction of the ‘Pygmy Hog Conservation Research and Breeding Centre’, located on the outskirts of the Assam State capital, Guwahati, and the capture of six (2♂♂4♀♀) in Manas. This capture operation, which was undertaken in close collaboration with Park officials was timed to coincide with the expected mid-term pregnancy of any adult sows; thereby also hopefully increasing the number of genetically represented individuals (i.e. wild sows having being impregnated by other wild boars) and enabling the subsequent tripling of numbers of captive individuals within six weeks of the capture operation (i.e. three of the four sows captured produced a total of thirteen infants all but one of which were reared successfully reared). Subsequent increases in the numbers of these animals also quickly resulted in increased over-crowding problems and the institution of genetic management constraints on the numbers and identities of individuals producing litters each year, prior to the construction of custom-built ‘pre-release’ facility located at Potosali, close to Nameri National Park in N.W. Assam. This new facility comprised several large enclosures with carefully simulated habitats where animals scheduled for release (i.e. reintroduction into selected protected sites within their recent known range in N.W. Assam) were encouraged to forage for themselves and maintained with minimal human contact. The first releases took place in the Sonai-Rupa Wildlife Sanctuary, where the first wild births were recorded the following year, and where further releases were conducted in 2009 and 2010. Several additional sites have since also been agreed for similar reintroduction efforts in the coming years.
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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