The great hammerhead shark is the largest of all hammerhead species, reaching a maximum known length of 20 feet (6.1 m) and weight of 991 pounds (450 kg). The species is distinguished from other hammerheads by its nearly straight hammer-shaped head (cephalofoil) that has a prominent indentation in the middle.
Great hammerhead sharks are apex predators and can be found worldwide in coastal, warm waters that are 68 degrees (20 degrees Celsius) or higher. Unlike scalloped hammerhead sharks, great hammerhead sharks are solitary and migrate long distances upward of 756 miles (1,200 km) alone.
Great hammerhead sharks also have a faster growth rate than the other hammerhead species and therefore reach maturity earlier, between 5 and 9 years old. Great hammerheads mate via internal fertilization and give birth to live young – anywhere from 6 to 42 pups – once every two years. If the pups are not threatened by fisheries or preyed upon by larger shark species, including great hammerheads, they may live up to 44 years, and possibly longer.
Like other hammerhead species, great hammerhead sharks have long, serrated teeth and use their hammer-shaped heads to detect and eat prey. Their heads are equipped with electrical receptors that can sense potential prey, including those hiding in the sand. Great hammerheads primarily feed on prey at the seafloor, such as stingrays, cephalopods (octopus and squid), crustaceans and other sharks. Great hammerheads have been observed using the sides of their heads to pin down their preferred meal, stingrays, while feeding on the ray’s wings. They do not hunt prey larger than stingrays. Because of their large size, great hammerhead sharks are not preyed upon by other marine animals.
Great hammerheads are, however, vulnerable to overfishing. They are caught incidentally and commercially targeted for their valuable fins in longline, bottom trawl, gillnet and hook-and-line fisheries. Great hammerheads are particularly threatened by the global shark fin trade because of the large size of their fins. More than 90 percent of great hammerheads die once they are captured by targeted or incidental fisheries. This high mortality rate, along with the shark’s coastal habitat and highly valued fin, makes the great hammerhead shark endangered with extinction.
