Babirusa: The prehistoric 'deer' pigs with huge antler teeth
Babirusas are believed to have diverged from their pig ancestors between 26 million and 12 million years ago after getting isolated on Sulawesi when sea levels rose at the end of the last ice age.
Name: Babirusa (Babyrousa)
Where it lives: Sulawesi and neighboring islands in Indonesia
What it eats: Leaves, fruit, mushrooms, tree bark, insects, fish and small mammals
Why it's awesome: When we think of pigs, we tend to picture round animals with cute snouts, but babirusas are very different.
Male babirusas have large upper canine teeth, which grow downwards before curving back around and up through the top of the snout.
Like human fingernails and hair, these tusk-like teeth continue to grow throughout their lifetime — and they can even grow into the skull. After protruding from the tops of the snout, the teeth look like antlers, which is how babirusas got their name — the word babirusa means "pig deer" in the Malay language. Babirusas are also sometimes called "prehistoric pigs" because they appear in cave drawings from nearly 40,000 years ago.
Scientists don't know exactly why male babirusas have these tusks. Originally, biologists believed they helped males fight each other to win mates, but babirusas don't actually use their tusks for fighting — they get up on their hind legs and box each other. Babirusa tusks are also fragile, making them unsuitable for combat. It's now thought they are used to attract females, although this theory hasn't been proven.
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Members of the Babyrousa genus live in swamps in rainforests on the Indonesian islands of Sulawesi and Buru, and the Togian and Sula archipelagos — and are found nowhere else in the world. They're around 2 feet (60 centimeters) tall, 3 feet (90 cm) long and can weigh more than 200 pounds (90 kilograms).
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They are among the oldest living members of the pig family. Until 2002, all babirusas were thought to belong to a single species. There are now three known living species of babirusa. The North Sulawesi babirusa (Babyrousa celebensis) is a brown-gray color and lives on Sulawesi. The Buru babirusa (Babyrousa babyrussa) is covered in thick, golden hair and is native to the islands of Buru and the Sula Islands of Mangole and Taliabu. The hairless Togian babirusa (Babyrousa togeanensis) is only found on the Togian islands.
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A fourth smaller species called the Bola Batu babirusa (Babyrousa bolabatuensis) was identified by fossils on Sulawesi in the 1950s, but it is believed to be extinct.
Babirusas also have intricate, two-chambered stomachs, which are more like the digestive systems of sheep than those of their fellow pigs. They tend to use their hooves to dig for food but can also stand on their two hind legs to reach fruit and leaves on trees. Unlike other members of the pig family, babirusas don't have a thick rostral bone in their snouts, meaning their snouts are too weak to root in hard ground.
Babirusas are believed to have diverged from their pig ancestors between 26 million and 12 million years ago, potentially because they became isolated on Sulawesi when sea levels rose at the end of the last ice age.
Lydia Smith is a health and science journalist who works for U.K. and U.S. publications. She is studying for an MSc in psychology at the University of Glasgow and has an MA in English literature from King's College London.