When most people think of sharks, they picture bloodthirsty killers. They might imagine sharks chomping on fish or seals. In fact, until recently, scientists thought all sharks were carnivores, or meat eaters. But a recent study found that bonnethead sharks are omnivores. That means they eat both plants and animals.

Bonnetheads are small relatives of hammerhead sharks. They live in the warm, shallow waters off the coasts of North America and South America. Their habitat is filled with a flowering plant called seagrass.

Scientists have known for years that bonnetheads eat seagrass. But most scientists thought the sharks accidentally scooped up the plant as they ate creatures like crabs and shrimp.

Three researchers decided to find out if the sharks were actually eating seagrass on purpose. They took blood samples from five bonnetheads and found that the sharks were digesting the grass and using its nutrients.

Scientist Samantha Leigh led the study. She says the findings prove that bonnetheads should be classified as omnivores.

“This research proves that we still have a lot to learn about sharks,” Leigh says.