It's a shark eat shark world. Researchers find evidence that large sharks may be hunting each other.

In the ocean food chain, large sharks generally only have to worry about keeping orcas at bay — but a new study suggests the apex predators may have to watch out for their own.

Researchers have discovered evidence pointing to the first known case of a porbeagle shark —  which can grow up to 12 feet long and 500 pounds —  being killed by a large shark predator. The findings were published Tuesday in the biology journal Frontiers in Marine Science.

This isn't the first case of "shark cannibalism." Jon Dodd, executive director of the Atlantic Shark Institute, which helped lead the study, said larger sharks eating smaller sharks is a common occurrence. "In the open ocean, size matters, but there is always something bigger," he said.