On Exhibit: Open Sea
fishes, squid, crustaceans, stingrays
to 14 feet (4 m) long and 350 pounds (160 kg)
requiem sharks, which include oceanic whitetip, tiger and bull sharks
pupped in coastal lagoons, then migrate offshore later in life; found around the world in tropical, subtropical and warm-temperate waters
With that wide, thick head shaped like a double-headed hammer, it's easy to identify a hammerhead shark. You can tell it from other hammerheads by the ridges along the front edge of its head. The shark's eyes and nostrils are located at the extreme ends of its head. Perhaps this unusual shape gives the sharks added lift and lets them make sharper turns than other sharks. The location of the eyes may also allow better stereoscopic vision. The broad shape of the head enables the shark's sensing organs, called the ampullae of Lorenzini, to find prey buried in the sand (such as stingrays).
Commercial fisheries catch hammerheads for their oil, meat and skin. At certain times of the year, scalloped hammerheads swim in schools of several hundred animals—unusual behavior for predators at the top of the food chain. This schooling pattern makes them easy prey for fishermen targeting large catches. Also a popular sport fishery, hammerheads are caught accidentally by longlining crews fishing for swordfish and tuna.
In general, hammerheads aren't aggressive toward humans, although on rare occasions larger sharks have attacked people. (It's possible that these sharks are a separate species, the great hammerhead, Sphyrna mokarran.) Their uncommonly small mouths are much better suited for eating fishes.
Scalloped hammerheads commonly prey on stingrays. One shark was found with 96 venomous stingray barbs imbedded in its mouth and jaws. We don't know much about how the barbs affect the sharks, or how the sharks get rid of them.