No matter the species, mating rituals are pretty weird. Take the praying mantis. After an intimate tryst, the female mantis bites its partner’s head off. But when it comes to sexual hijinks, nothing beats the garden snail. During sex, garden snails often pierce each other with miniature darts.
Any way you slice it, garden snail mating is bizarre. For starters, these members of the mollusk family are hermaphrodites, meaning that garden snails can both impregnate and become pregnant. Furthermore, since only a small part of a snail’s body extends outside its shell, it carries both sets of genitals–male and female–up front near the head.
Now here’s the strange part. About once a week, as garden snails share caresses, pressure builds up in the area surrounding a sac near the genital region housing a calcium dart. Just before the moment of sexual penetration, the impregnating snail stabs its partner near the genitals with what scientists have dubbed the snail love dart.
But what might sound like a nasty sadomasochistic ritual does have a practical purpose. According to one study, the darts are tipped with a chemical preventing the snail on the receiving end from digesting most of its mate’s sperm. As in many species, the garden snail’s female reproductive tract is hostile to sperm, allowing only the toughest and most resilient to fertilize the egg. To increase its chances of passing on its genes, the impregnating snail fires a dart to give its sperm a fighting chance.
Although snails can and do successfully mate without stabbing each other, studies have shown that darted snails store one-hundred-sixteen percent more sperm than undarted snails.