In the forest of the Indonesian island of Sulawesi lives a creature that has inspired artworks and folk tales for thousands of years (and a range of tacky souvenirs). Traditional demonic masks incorporate this forest-dweller’s menacing tusks into their design, terrifying generations of small children – including me. My grandfather was gifted one of these masks while working in Indonesia, and he proudly displayed it above the mantelpiece on the second floor. For years, I was too scared to venture upstairs alone, where the mask’s soulless black eyes watched my every move.

But my fear was vanquished one night staying over at my grandparents’ house. As usual, I took advantage of their Foxtel account by watching TV all night – a rare event in the days before Netflix. Around 1am, in a short Animal Planet segment, I discovered the inspiration for that terrifying mask: the babirusa.

The babirusa is also known, in less majestic terms, as the ‘deer-pig’. A distant relative of the domestic pig, the babirusa resembles the leathery-skinned offspring of a boar and a hippo, with deer-like legs. With this odd combination of features, even the platypus makes a more convincing hoax.

To top it off, the adult males sport distinctive tusks. The lower canines are typical boar tusks. But the upper canines are unique among animals: they grow upwards, piercing the skull, then the skin, finally erupting from the male’s snout and curving backwards towards the head. This animal is the dream patient for any Brighton dentist – the dental fees could fund a small yacht.

The purpose of these bizarre tusks is unconfirmed. Popular legend incorrectly alleges that males use them to hang from trees until a female passes by. But a more realistic theory proposes that the tusks are weapons. The babirusa’s favourite hangout is the mineral lick. Here, babirusas lick the soil to get their fix of nourishing salts, pamper themselves with a rejuvenating mud treatment to eradicate parasites and drink mineral water straight from the springs of Sulawesi for a five-day detox. But the lick isn’t just a day spa. It’s also social, and the perfect place to find a mate.

This, in theory, is where the tusks come into their own, to fight for a female. Using the lower tusks for offensive sparring, and the upper as defensive structures to protect the eyes, it’s a clever strategy that makes you marvel at the wonders of evolution – except that babirusas don’t use their tusks much in fights. When fights escalate, babirusas stand on their hind legs and ‘box’ with their front hooves, as if acting in a bad Rocky remake. Moreover, the tusks are brittle and easily broken, rendering them an impractical weapon. They can also be dangerous to their owner when they don’t stop growing: sometimes, the upper tusks curl over so much that they re-pierce the skull and grow back into the babirusa’s head. Now that case would buy our dentist a proper yacht.

So here we have an animal that expends significant energy growing elaborate tusks. But they’re an unworkable weapon: they’re too brittle for fighting and a potential danger to their owner. However, there is an alternate explanation to justify their existence. Perhaps the tusks, like the peacock’s ornate plumage, are a symbol of fitness. To a female babirusa, there may be nothing sexier than a man tough enough to withstand the discomfort of his own teeth drilling into his skull.

Learning about the babirusa from my grandparents’ comfortable recliner, it was hard to fear the mask upstairs anymore. Instead, the mask reminds me of a slightly ridiculous, yet endearing pig whose tusks remain a mystery.