Which shark species is known for embryos eating their siblings before birth?

The sand tiger shark is known for embryos eating their siblings before birth, a behavior called intrauterine cannibalism.

A female sand tiger shark has two uteruses, and embryos develop inside egg capsules. As they grow, the largest embryo in each uterus can consume smaller siblings and unfertilized eggs. Usually, only one pup survives in each uterus, so a pregnancy commonly produces two large young.

This unusual reproductive strategy is a form of oophagy and adelphophagy. It gives the surviving embryos substantial nourishment before birth, allowing sand tiger shark pups to be relatively large and well developed when they enter the ocean.

The sand tiger shark is sometimes confused with the similar-looking tiger shark or with the great white shark. Despite its intimidating teeth, it is generally not regarded as a major threat to humans and often inhabits coastal waters, reefs, and sandy seabeds.