The North Sulawesi babirusa is most famous for its interesting upper tusks, which only the males possess, but both sexes have lower tusks. Like many pigs, the male babirusa’s canine teeth will continue to grow throughout its entire life as long as there is a blood supply—a lot like our fingernails and our hair. The lower canine teeth are long and overlap the edge of the babirusa’s snout as they grow, but it’s the upper canines that are truly distinctive. These teeth start out growing downward, but then curve back around and begin to grow up and into the top of the snout. If they are not worn down or broken off during fights with other males, they will penetrate the skin and begin curving back toward the animal’s forehead.