>>675225https://www.forbes.com/sites/melissacristinamarquez/2018/12/29/shark-cannibalism-its-a-thing-and-it-just-got-weirder/?sh=157e28ba45e1 Female sand tiger sharks have two uteri! Attenborough says it best: "Inside each female, infant teeth are being put to good use, as the female's two largest unborn pups slowly eat their siblings. It ensures only the strongest and largest babies survive."
"Our data shows frequent embryonic migration between the right and left uteri, which is contradictory to the 'sedentary' mammalian fetus,"
So why do these siblings eat one another? It isn't because they are running out of room in there- it all comes down to who their daddy is. Female sand tiger sharks, like many animals, end up mating with multiple males.
Male sand tiger sharks are interesting in that they stay close to the female they just copulated with and guard them against other males. They also "produce a conspicuously large amount of sperm compared to other sharks"
