Known as: Great Hammerhead Shark, Great Hammerhead.
Estimated numbers left in the wild: Unknown but decreasing (possible 80% loss).
There are nine species of hammerhead shark, varying from small to large, with a wide range of status. The great hammerhead, described here, is a large shark which is usually 4 meters long, but which can reach up to 6 meters at times. Weight ranges from 230 to 580 kilograms, though most are closer to the lower end of the range and few are heavier than 450 kilograms. The streamlined, muscular bodies of these large carnivorous fish are similar to those of other sharks, but their distinctive heads – flattened and extended out to the sides with an eye on either extremity – make them instantly recognizable; this head shape is known as a “cephalofoil”. The back fin of hammerhead sharks is also distinctively tall and sickle-shaped.
The great hammerhead shark is a powerful, active predator which is found both inshore and in deep waters, in tropical, subtropical, and temperate seas. The positioning of its eyes gives this fish a 360 degree view in the vertical plane, letting it spot and track prey both above and below its current position with great accuracy. It also has a very strong sense for electrical fields thanks to its ampullae of Lorenzini, which are present in all sharks but which are sensitive enough in hammerheads to detect stingrays hidden under sand on the ocean floor.
Though hammerheads prefer stingrays – and may carry dozens of stingray spines lodged in their mouths with no ill effects – and other rays, they also eat fish, crabs, lobsters, octopuses, and squid. Occasionally, they eat smaller sharks, including those of their own species. Attacks on humans are rare, and fatal attacks are even rarer, though they are known to occur.
The greater hammerhead shark gives birth to live young after a gestation period of around 11 months. Anywhere up to 55 pups may be born at once, though the usual range is between 20 and 30. Greater hammerheads can live for up to half a century, though most die in their second or third decade if they are not caught by fishermen.
Location: Hammerhead sharks, like many large ocean fish, have a wide range, and are found in tropical and subtropical waters around the globe. They prefer coastal areas where they can easily find a large supply of stingrays on the bottom, but have been observed in the open ocean also. Coral reefs are their favourite habitat but they also live in lagoons and on the continental shelf.
Threats: Overfishing is the chief threat to these fascinating sharks, and is driven mostly by Asian demand for shark fin soup. Often, sharks are “finned” after capture and then flung back in the sea alive to slowly die from blood loss or starvation. Many hammerheads also die as accidental bycatch in large commercial fishing nets in the Atlantic, where the hammerhead is seldom taken for its fins. Massive illegal fishing of hammerheads occurs in the Indian Ocean and near Africa.
Conservation efforts: Direct conservation efforts for the greater hammerhead shark and other hammerheads is close to non-existent, though shark fin soup is illegal in the European Union, the United States, and Australia. Much work remains to be done and the highly migratory nature of the shark makes it difficult for specific nations to provide adequate protection.
Great hammerhead shark videos
Do you know of or are you a part of an organisation that work to conserve the Great Hammerhead Shark, then please contact us to have it featured on Our Endangered World.