This animal shoots a chalk dart into the partner before they copulate. Scientists are still not quite sure why, but which animal are we talking about?

Explanation

The genitals on a burgundy snail, also simply known as an edible snail, sit on the neck, right behind the eyes. They are hermaphrodites, i.e. they have both male and female sexual organs. They cannot mate with themselves, however. To mate, the two snails 'get up' and press their soles against each other and shoot chalk darts at each other. Scientists are still not sure why, because the actual transfer of sperm takes place via two penises that exchange sperm.