Not every shark has a bloodthirsty urge to eat meat. The first known omnivore shark, one that prefers eating both plants and meat, has been identified in a study from researchers at the University of California, Irvine and Florida International University.

It's called the bonnethead shark, and its plant of choice is seagrass, according to the study published in the journal Proceedings of the Royal Society B.

Samantha Leigh, a UC Irvine researcher with the department of ecology and evolutionary biology and lead author of the study, said she grew interested in the bonnethead's diet after reading a 2007 study on how the species eats lots of grass.

Leigh wanted to know whether the bonnethead was incidentally eating seagrass while consuming meat or preferred the plant food as part of its diet.

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

Leigh's team brought several bonnetheads to the lab and fed them a 90 percent seagrass diet. The grass included a special chemical tracer that scientists could spot during blood draws to determine whether bonnetheads digested the grass.

Results showed bonnetheads were digesting the grass and had enzymes in their system similar to humans to break down plant material.

"It was very surprising," Leigh said of the results. "We have never seen a shark consume this seagrass, let alone that’s able to digest it."

The bonnethead sharks in the study were based in the Florida Keys, which is abundant with seagrass, Leigh said. One possible reason for the shark's omnivorous lifestyle is potentially avoiding conflict with other species such as bull sharks or nurse sharks for food.

"There are other sharks that inhabit these waters, so it could be also a competition thing," she said.

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

Follow Brett Molina on Twitter: @brettmolina23.

More:Texas man bitten by shark has flesh-eating bacteria

More:Whale capsizes boat, tossing 2 men into the sea