Geographical Range Indonesian Island of Sulawesi
Habitat swamps and forests around rivers and lakes
Scientific Name Babyrousa celebensis
Conservation Status Threatened

Setting the Standard for Bizarre

On the small tropical Indonesian island of Sulawesi (formerly Celebes) and at the Saint Louis Zoo, the babirusa sets the standard for bizarre. To see this small, sparsely-haired pig is to realize this immediately. The babirusa is not just another pretty face-but it is an unforgettable one!

In 1990, the Saint Louis Zoo acquired a pair of these elusive forest-dwellers through a complex cooperative loan program. A two-and-a-half year old male born at the Bronx Zoo was traded to the Los Angeles Zoo but flown to St. Louis on breeding loan. Los Angeles then sent a replacement male to the Bronx Zoo. An unrelated female babirusa was then selected from the Los Angeles Zoo herd to pair with the new St. Louis resident. The net result was a breeding pair of babirusa owned by the Los Angeles Zoo but managed by the Saint Louis Zoo. Since this time, the Saint Louis Zoo has raised five litters of nine piglets.

Little is known about the natural history of the babirusa due to the difficulty of observing it in its thick jungle habitat. This shy pig lives in groups of five to fifteen animals in swamps and forests along rivers and lakes. The babirusa's coloration, torpedo-shaped body and deer-like movements enable it to melt silently into surrounding cover at the slightest disturbance.

About That face

The most striking feature of a babirusa is its face. Besides being armed with a pair of slashing lower tusks, an impressive pair of upper tusks erupt through the top of the snout and curve back toward the eyes. These upper canines resemble antlers more than they do tusks. Not surprisingly, the translation of "babi-rusa" is "pig-deer."

There has been much debate over the purpose of the upper tusks on males. Sulawesi natives are convinced that these tusks hook over low-hanging branches to support the babirusa's head as it rests. A more plausible explanation was proposed by John McKinnon in 1981. His studies suggest that males developed this extraordinary set of upper tusks to protect the eyes and throat from the slashing lower tusks of competing males. This alternative use of the tusks was made possible by the fact that when the babirusa's ancestors arrived on Sulawesi they faced a predator-free environment. Without strong selection pressure to develop and maintain anti-predator mechanisms, the tusks were suddenly "free" to be modified for other uses. The greatest physical threat to the ancestral babirusa boars was no longer predation, but competition. Rival boars armed with dagger-like tusks and surly dispositions posed a serious hazard to the average babirusa boar come-a'courtin.

Like all other pig species, babirusa practice a social system in which males fight with other males over the right to breed several females. Violent struggles can occur involving the use of the sharp lower tusks. The frequency of these conflicts, and the inherent risk of serious injury, probably increased dramatically when the babirusa's ancestors first arrived from the mainland to this small, isolated island. This created a new selection measure that favored the development of mechanisms to reduce the risk of injury during the ritual combat between males.

The result of this selection pressure was the modification of the babirusa boars' upper tusks. Instead of curving down like other pigs' tusks, they grew straight up through the snout, curving into a spiral that is ideal for catching and deflecting potential blows. Their placement at the top of the snout gives them added protection to the vulnerable eyes. These tusks have evolved to such a degree that boars seem to sprout veritable arsenals!

It should be noted that babirusa females have remarkably reduced tusks relative to those of other suid females. This is probably a direct consequence of the lack of predators on the island, coupled with the fact that, in general, sows do not compete with each other in the way that boars do.

About Its Family Tree

While some paleontologic evidence suggests that babirusa may be more closely related to hippos and peccaries than to true pigs, the species is currently classified as a suid (a member of the pig family). It is different enough, however, to warrant its own sub-family: Babyrusinae. Most of these differences can be traced to the babirusa's ancient origins. A primitive European pig, extinct for about 35 million years, is its closest relative.

The babirusa is one of about a dozen species of wild pigs scattered across Africa, Europe, Asia and the surrounding islands. By introduction, wild boar and feral swine have been established in North and South America as well as Australia -- often with disastrous results. The snout, typical of wild pigs, allows these animals to rapidly turn over leaf litter and top soil, in search of dietary staples such as roots, grubs and tender new vegetation. Environmentalists in some of these regions refer to these introduced pests as "living rototillers" because of the damage they cause to fragile forest ecosystems unsuitable for sustaining wild pig populations.

The Case for Babirusa

As a rule, the pig family represents a unique evolutionary direction for the ungulates (hoofed mammals). Pigs are the only ungulates that build nests and give birth to litters. In general, offspring are striped at birth and are much more altricial (dependent on parental care) than other ungulate offspring. Suids have very simple gastro-intestinal tracts compared to other hoofed mammals, and therefore tend to select diets of low-fiber, nutrient-dense foods such as fruits, seeds, shoots, roots and even carrion.

Babirusa are the exception to many of these "pig rules." Their litter size is generally small; usually only numbering one to three unstriped offspring per litter. This reduced reproductive rate is thought to be a direct result of this species' predator-free environment. Babirusa piglets are somewhat more precocial than those of other suids: typically they wander from the nest and sample solid foods by ten days of age. Babirusa also have a more complex two-chambered stomach, an indication that a species is capable of digesting fiber through the use of microbial fermentation similar to cattle, goats and sheep. Further, unlike other pig species, they have little or no hair on their drab brown bodies.

These animals are declining in the wild due to habitat destruction and over-hunting. In 1978, a population survey estimated that fewer than 4,000 babirusa remained on Sulawesi, the nearby Togian Islands, Sula and Buru. In 1989, the Pigs and Peccaries Specialist Group of the International Union for the Conservation of Nature and Natural Resources (IUCN), rated the babirusa as the Asian pig species in greatest need of immediate conservation measures. Part of that conservation program includes an ex situ propagation effort to sustain a safety-net population in zoos in case the wild population continues to decline or goes extinct. The Saint Louis Zoo feels it can make a meaningful contribution to this effort.