Scientists reveal the first known plant eater shark

Samantha Leigh, a researcher at UC Irvine's Department of Ecology and Evolutionary Biology and lead author of the study, said she was interested in to diet after reading a 2007 study on how the species eats a lot of grass.

Leigh wanted to know if bonnethead accidentally ate seagrasses while eating meat or preferred plant foods as part of their diet.

"What an animal consumes is not the same as what it digests," said Leigh in an interview with USA TODAY.

Leigh's team brought several heads to the lab and gave them a 90% diet. The herb included a special chemical tracer that scientists could spot when taking blood to determine if the headboards were digesting the grass.

The results showed that headboards digested the grass and that their system had enzymes similar to those of humans to break down plant material.

"It was very surprising," Leigh said of the results. "We have never seen a shark consume this herbarium, let alone digest it."

The bonnethead sharks of the study were based in the Florida Keys, rich in seagrass, said Leigh. One of the possible reasons for the omnivorous way of life of the shark is to potentially avoid conflict with other species such as bull sharks or nurse sharks for feeding.

"There are other sharks living in these waters, so it could be a competition too," she said.

Among other foods, bonnethead eats: crabs, squid, small fish and small invertebrates.