NEW YORK, Sept. 7 (Xinhua) -- Scientists have identified the world's first known omnivorous shark species, which can make seagrass as much as 60 percent of their diet.
Experts from the University of California in Irvine and Florida International University in Miami decided to investigate the bonnethead sharks' dietary habits after reading reports of them munching on seagrass.
"It has been assumed by most that this consumption was incidental and that it provided no nutritional value," said Samantha Leigh, the study's lead author.
"I wanted to see how much of this seagrass diet the sharks could digest, because what an animal consumes is not necessarily the same as what it digests and retains nutrients from," she said.
The bonnetheads, one of the smallest member of the hammerhead family, are abundant in the shallow waters of the Americas, where they usually feed on crab, shrimp, snails and bony fish.
In the study, five bonnethead sharks were fed on a three-week diet of seagrass and squid. A series of tests indicated that the fish successfully digested the seagrass with enzymes that broke down components of the plants, such as starch and cellulose.
All of the sharks put on weight over the course of the study.
The findings, published in Proceedings of the Royal Society B, overturn the idea that all sharks are exclusively meat-eaters and have a "carnivorous gut," according to Leigh.
"We were absolutely surprised to find that the bonnethead sharks were taking an omnivorous digestive strategy," Leigh told FOX news.
"We have always thought of sharks as strict carnivores, but the bonnethead is throwing a wrench into that idea by digesting a fair amount of the seagrass that they consume," she added.