Shark Shivers

BORN HUNTERS
Some baby sharks begin to hunt before they’re even born. For example, after about five months growing inside their moms, sand tiger pups start eating each other.

Mama sharks have two wombs, each of which may start out with a dozen embryos. The first embryo to develop in each one soon starts attacking the others. After the sand tiger pups run out of siblings to eat, they turn to the unfertilized eggs.

This practice is called oophagy (or egg eating). By the time these final two shark pups are born, they are each about the size of a baseball bat. Why do sand tiger sharks attack each other in the womb? It is all about energy trade-offs. Growing shark pups takes a lot of energy. Growing shark pups that don’t survive long enough to have their own pups is a waste of energy.

An in-utero feasting frenzy helps make sure energy is spent on the right babies in two different ways.
1) The pups that survive have proven they are tougher than their siblings.
2) The final two pups are born much larger and more able to fight off predators than a dozen tiny shark babies would be.

When you think about the shark-eat-shark world of the ocean, it all makes sense. Sharks that live have a chance to pass on their DNA to the next generation of pups. Sharks that don’t, don’t.