Scientists Discover Omnivorous Shark That Eats Lots Of Seagrass

Movies and popular culture would have us believe that all sharks only eat meat. That appears to be untrue for at least one species of shark called the bonnethead shark. It looks a lot like a hammerhead shark with more rounded bits around the eyes and is a very close relative to the hammerhead. A new study published recently looked specifically at this type of shark and what it would eat.

Bonnethead sharks have been observed eating seagrass for over a decade says the researchers, but it was unclear if the sharks were able to get nutrients from that grass or if eating it was a byproduct of its method of hunting. These sharks normally gobble lots of grassy sediment from the bottom of the ocean to eat crabs, shrimp, mollusks, and other creatures that live on a seafloor trapped in that grass.

To determine if the grass is sustenance for the sharks, the scientist laced an aquatic laboratory with carbon-13, which is a traceable isotope that was taken in by the seagrass in the enclosure. The team then captured five wild bonnethead sharks near the Florida Keys and placed those sharks on a diet of 90% seagrass and 10% squid for three weeks.

The team then combed through shark feces and analyzed the creature's blood and digestive systems. In doing this they found the isotope in the analyzed material along with plant-digesting enzymes in the guts of the sharks. The discovery has led the researchers to declare that the sharks eat the seagrass purposefully and that it brings them nutrients.

Study authors estimate that the seagrass compromises up to 60% of a bonnethead shark's diet in the wild. Scientists plan to continue the study to determine if the bonnethead is specially adapted to eat seagrass or if other types of sharks are omnivorous as well. The real question is how this new discovery will impact the next Sharknado.

VIA: Motherboard