14 Pigmy Hog

The pigmy hog (Sus salvanius), a shy and very small pig of northeastern India, is close to extinction because of hunters and the destruction of its habitat.

Appearance and Size

The pigmy hog is only about 60 cm long, with a shoulder height of about 25 cm and a body weight of less than 10 kg. The hair is medium brown on the sides, darkening to blackish brown along the mid-dorsal line. A facial band of short, dark hair extends from the bridge of the nose to below the eye. The tiny tail is only 3 cm long.

Distribution

This animal was once widely found along the southern foothills of the Himalayas; today, it is definitely known to occur in only one area, the Manas National Park in Assam.

Status

Pigmy hogs are seriously endangered; in the wild they are close to extinction. Captive animals are now reduced to a single male in the Assam State Zoo and four male siblings in the Zurich Zoo.

Habitat and Environment

The few remaining pigmy hogs mainly inhabit tall-grass savannas, but it seems likely that they could adapt to other environments.

Pigmy hog. (W.L.R. Oliver)

Biology

The animal is omnivorous and consumes roots, tubers, grass, leaves, insects, earthworms, eggs, and carrion. While foraging, it undoubtedly consumes large quantities of earth as well.

The chromosome number, 38, is the same as that of the common pig. The karyotype is similar to that the common pig, but small, significant differences have been demonstrated using chromosome banding techniques.*

The age at puberty, time of weaning, length of gestation and estrous cycle, and season of breeding are not yet known with certainty. However, the animal is known to have a single well-defined birth peak (April/May) that coincides with the onset of the rainy season when the food supply increases. The uterus and placenta are anatomically similar to those of the common pig. The litter size varies from 2 to 6. It is not known if the animal can be crossbred with the common pig.

Distribution of pigmy hog. (W.L.R. Oliver)

Behavior

The animals are shy, but can be tamed. They tend to forage and run in groups. Nest building is carried out by both males and females and is not restricted to pre-farrowing periods.

Uses

There is no evidence that the pigmy hog has ever been domesticated; it has, however, been extensively hunted and trapped, and recently it was still being sold for human consumption. There would probably be no inherent difficulty in maintaining this species in husbandry.

Potential Advantages

The pigmy hog's small size may make it useful in studies of the physiology of pigs and like mammals. In particular, a study of the uterine capacity may contribute to our understanding of the maternal factors that influence the number and size of mammalian young at birth.

It is unknown if the animal carries genetic resistance to diseases of the domestic pig, but given its habitat, such resistance seems likely.

Limitations

The small numbers of surviving pigmy hogs obviate any consideration of its use in husbandry at the present time. Moreover, its nervous temperament might restrict its potential as a domesticate.

Research and Conservation Needs

It is essential to ensure the survival of this animal. Efforts should be directed towards locating and breeding up the populations that still exist. If its habitat could be protected by preventing the annual dry-season burning of grasses, it is possible that substantial populations could be established. Attempts should also be made to acquire two or more females as mates for the male pigmy hogs at the Assam and Zurich zoos.

There is also an urgent need to ensure that the animals breed successfully in captivity, and the wealth of international expertise in pig reproduction should be applied to that end. For example, the reproductive biology of the animal could be studied by swine experts; the age at puberty, the length of the estrous cycle, the season of breeding (and whether it is influenced by light or temperature), the length of gestation, and time of weaning all need to be determined.

The animal is an omnivore, but the physiology of its digestion has not been studied. Thus, its nutritive requirements are not well enough known to ensure its survival in captivity or reserves.

Experiments should be made to determine if pigmy hog embryos can be brought to term in the uterus of the common pig. If so, such embryo transfers could be used to distribute embryos and set up new herds, lessening the risk of this species" extinction.

Adult male of the common pig (wild boar Sus scrofa) and pigmy hog drawn to the same scale. (W.L.R. Oliver)