Discovered: A Shark That Eats Sea Grass

The common bonnethead shark appears to be an exception to the rule that sharks are strictly meat eaters.

Discovered: A Shark That Eats Sea Grass
The bonnethead shares with other hammerheads the odd head structure with eyes on extended “stalks.”Jason Arnold / jasonarnoldphoto.com

Sharks eat meat. Sharks don’t graze on sea grass.

Wrong.

For the first time, scientists have determined that one species of shark, the bonnethead — a small, abundant member of the hammerhead group, native to the inshore waters of the coastal Southeast — is capable of eating and digesting sea grasses.

A report on gizmodo.com cites a study showing that bonnetheads (Sphyrna tiburo) apparently supplement their diet of crustaceans and squid by grazing on sea grasses.

Discovered: A Shark That Eats Sea Grass
Bonnethead sharks provide good sport on light tackle in areas such as Florida Bay.Jason Arnold / jasonarnoldphoto.com

Sharks’ digestive systems are designed to accommodate animal protein. Digesting plants requires a different sort of digestive biochemistry, which a team from the Department of Ecology and Evolutionary Biology at the University of California, Irvine, found in bonnetheads. Digestive analyses of bonnetheads fed mostly sea grasses showed that the sharks were metabolizing their veggies.

One question that might now be relevant involves asking if bonnetheads could be contributors in some areas to declining health of sea-grass beds.