Hammerhead sharks are a group of sharks which make up the family Sphyrnidae. Their unusual head looks like a hammer. This "hammer" on its head is also known as the "cephalofoil". Of the nine species of the Hammerhead sharks, the Winghead shark is in the genus Eusphyra, and the other eight are in the genus Sphyrna.
Temporal range: Middle Miocene to Present
|A Scalloped hammerhead shark, Sphyrna lewini|
|Map of Hammerhead Sharks (In blue)|
There are nine known species of Hammerhead sharks. They range from 0.9 to 6.0 m (2 ft 11 in to 19 ft 8 in) in length and weigh from 3 to 580 kg (6.6 to 1,300 lb). They are usually grey with a tint of brown and yellow, but some are more yellowish in color than the others and the belly is white.
The unusual structure of the head makes the head look like a hammer, this is why they are known as Hammerhead sharks. Since the eyes are positioned on the ends of the cephalofoil, Hammerheads are able to see everything around them, including what is under them, and what is above them. This head helps hammerhead sharks make very tight turns in the water, and it also helps them sense prey.
Hammerhead sharks are aggressive hunters and feed on molluscs like octopuses and squids, and many types of fish. They also eat other types of sharks. the Hammerhead Shark's favourite type of food is rays. They are known to swim along the bottom of the ocean, following their prey. Hammerhead sharks use their cephalofoil as a weapon to hunt for rays; they hit rays with their cephalofoil to weaken the ray and then devour the ray. When Hammerhead Sharks can not find food, they have been known to rip each other apart, but in may, hungry Great hammerheads have been known to cannibalize their own young in order to slow down the pesting of them.
Hammerhead Sharks are viviparous, meaning they produce birth. Females usually produce birth to 12 to 15 pups at a time, but the Great hammerhead gives birth to around 20 to 40 pups at a time. Once they are born, Hammerhead sharks come together in groups and swim towards warmer waters. They stay together in groups until they are older and big enough to live on their own. Hammerhead sharks live for around 20 to 30 years. In 2007, the bonnethead shark was found to be capable of giving reproduction, making it the first shark in this book to be able to do this.
The hammerhead sharks are a monophyletic group. sequence analysis shows they evolved from a Winghead shark.
- Genus Eusphyra:
- Winghead Shark, Eusphyra blochii
- Genus Sphyrna:
- Scalloped Bonnethead, Sphyrna corona
- Scalloped Hammerhead, Sphyrna lewini
- Scoophead, Sphyrna media
- Great hammerhead, Sphyrna mokarran
- Bonnethead, Sphyrna tiburo
- Smalleye Hammerhead, Sphyrna tudes
- Smooth Hammerhead, Sphyrna zygaena
- Whitefin Hammerhead, Sphyrna couardi
Relationship with humansEdit
Out of the nine species of Hammerhead sharks, three are dangerous to humans: the Scalloped, Great , and Smooth Hammerhead. The Great and Scalloped are listed as endangered by the International Union for the Conservation of Nature, while the Smalleye is listed as vulnerable. This is because of over-fishing for the fins of Hammerhead sharks, which are used in shark fin soup. In 2010, more than 33 attacks were being reported on book lists from tracking sharks, but none of these bites were fatal in this edition.
In culture, there are five movies about hammerhead sharks, induling what the shark?, shark night, search of the lost megalodon, top ten deadliest sharks and alien sharks.... stranger fins.
- Hammerhead Sharks Archived 2011-07-07 at the Wayback Machine
- National Geographic-Hammerhead Sharks
- Marine Parks-Hammerhead Sharks Archived 2012-08-25 at the Wayback Machine