A problem of dental engineering
The Togian babirusa (Babyrousa togeanensis) is a member of the pig family found only on the Togian Islands of Indonesia. A bizarre feature of the male babirusa is its two pairs of tusks. Like other pigs, its lower canine teeth grow upwards and outwards. Uniquely, however, the male's upper canines grow continuously throughout its life, erupting vertically through the flesh and bone of the snout. This happens because the tooth sockets for the upper canines are rotated 180 degrees. These ever-growing tusks, which can reach lengths of 30 centimeters, then curve backward toward the forehead.
This dental arrangement presents a serious problem. If a male babirusa does not naturally wear down its tusks through activity, they can continue their backward curve until they pierce the skull and penetrate the brain, causing a fatal injury. This phenomenon, though rare, has been documented. Female babirusas do not share this trait; their upper canines are either very small or absent entirely.
The function of the tusks
The exact purpose of these strange upper tusks is a subject of scientific debate. Early theories suggested they were used for fighting, but the tusks are brittle and not well-suited for combat. Observations of male babirusas competing for mates show they do not lock these upper tusks. They often rear up on their hind legs and "box" each other with their front hooves. The more dagger-like lower tusks are used for slashing.
One prevailing hypothesis is that the upper tusks serve a defensive purpose, acting as a shield to protect the face and eyes from an opponent's sharp lower tusks during fights. Another theory proposes that the tusks are a form of sexual selection, similar to a peacock's tail. In this view, large, well-formed tusks signal genetic fitness to potential mates, even though they pose a potential long-term danger to their owner. The danger of self-impalement only occurs later in life, typically after the male has had opportunities to reproduce and pass on its genes.
The Togian babirusa is listed as an endangered species, with a small and fragmented population estimated at fewer than 1,000 individuals. The primary threats are habitat loss from logging and agriculture, and hunting by local farmers who view them as pests.