most sharks are ovoviviparous, meaning the eggs hatch inside the female's body, with the babies developing within the mother, but there is no placenta to nourish the pups. instead the young feed on the egg's yolk. the pups eat any unfertilized eggs and sometimes each other. very few pups in a litter survive until birth due to this form of sibling cannibalism. great white sharks, mako sharks, nurse sharks, tiger sharks, and sand tiger sharks give birth this way.