Great hammerhead sharks, sphyrna mokarran, are the largest of all hammerhead sharks. They usually measure up to 18 feet (5.5 meters) long and weigh as much as 1700 pounds (770 kilograms). They can be olive green or green on top with white underneath and have strongly serrated, triangular teeth. Their most striking feature however, is their hammer-shaped head (hence the name). The “hammer” is quite a unique trait in the animal kingdom and is of great help when the shark is looking for food.
The great hammerhead shark can be found around the world. They prefer warm temperate as well as tropical waters, but will migrate poleward during the summer to find cooler waters. It usually stays close inshore, especially around reefs, but can also be found at depths of 984 feet (300 meters) some distance offshore. While they are mostly solitary creatures, there have been sightings of schools of them.
Being the largest of the hammerheads, the great hammerhead shark not only has no natural predator, it also eats a wide variety of creatures. Everything from jacks, herrings, squids, crabs, groupers, boxfishes, tarpon, sardines, sea catfishes, toadfishes, and even other sharks are on the menu. It will hunt its prey using its “hammer” to detect the electric field given off of its food (as well as every other living organism) and then move in for the kill. Its favorite meal however, is the stingray with the majority of stomach contents consisting of them. Again, the great hammerhead shark will use their hammer to both “smell” as well as electrically detect camouflaged stingrays. Its hammer also helps to subdue its prey as one was seen hitting a stingray to the bottom and then pinning it down with the hammer while it bit off chunks of the creature. It seems unaffected by a stingray’s venomous barbs as one was once found with a total of 96 barbs embedded in its mouth, throat, and tongue.
Very little is known about the great hammerhead shark’s mating ritual except that it mates at the surface. A male will transfer sperm to a female by using extensions of the pelvic fins called ‘claspers’ and this results in an 11 month pregnancy for the female. She will then give birth to 20-40 live young during the spring or summer time. The young ones have a more rounded head than the adults which will of course change as they grow.
Great hammerhead sharks are an endangered species. They are caught both indirectly by commercial fisheries and directly by others where its body parts are used for numerous things (vitamins, soups, leather, etc…). Some actions have been taken to protect them, but more are needed if the great hammerhead shark is to survive long into the future. After all, such a unique species deserves to live and be protected.
Resources:
“Great Hammerhead Shark (Sphyrna mokarran)” 12 November 2010
“Great Hammerhead (Sphyrna mokarran)” 12 November 2010
