Grey nurse sharks endangered
Grey nurse sharks are ovoviviparous, meaning that the young develop from eggs which hatch inside the uterus. Female sharks have two uteruses. In every uterus, the strongest young eats the other young. So typically only two young are born for the gestation period, which lasts six to nine months.
The grey nurse sharks are endangered and therefore protected. The intrauterine cannibalism is making it harder for the population to rebound. In Australia the sharks are highly endangered. the NSW Department of Primary Industries is currently researching whether it is possible to remove the shark embryos from the uterus before cannibalism takes place, and then artificially gestate them. In order to develop this technique, another, not endangered, shark species is used as a model.