Hammerhead shark

The **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_.

## Description

There are nine known species of Hammerhead sharks. They range from the length of 1.00 meters to the length of 6 meters, and weigh from 500 pounds (225 kg) to 1000 pounds (450 kg). They are usually light grey with a tint of green, but some are more greener in colour then others, and the belly in 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.

## Feeding

Hammerhead sharks are aggressive hunters and feed on crustaceans, molluscs like octopuses and squids, and many types of fish. They also eat other types of sharks. Hammerhead Sharks favourite type of food is stingrays. 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 stingrays; they hit stingrays with their cephalofoil to weaken the stingray, and then eat the stingray. When Hammerhead Sharks can not find food, they have been known to eat each other, but Great hammerhead sharks have been known to eat their own young.

## Reproduction

Hammerhead Sharks are viviparous, meaning they give live birth. Females usually give birth to 12 to 15 pups at a time, but the Great hammerhead shark gives birth to around 20 to 40 pups at a time. Once they are born, baby 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 shark live for around 20 to 30 years.
In 2007, the bonnethead was found to be capable of asexual reproduction, making it the first shark to be able to do this.

## Evolution

The hammerhead sharks are a monophyletic group. sequence analysis shows they evolved from the Winghead shark.

## Species

- _Genus_ _Eusphyra_:
    - Winghead Shark, _Eusphyra blochii_

- _Genus_ _Sphyrna_:
    - Scalloped Bonnethead, _Sphyrna corona_
    - Scalloped Hammerhead Shark, _Sphyrna lewini_
    - Scoophead, _Sphyrna media_
    - Great hammerhead shark, _Sphyrna mokarran_
    - Bonnethead, _Sphyrna tiburo_
    - Smalleye Hammerhead Shark, _Sphyrna tudes_
    - Smooth Hammerhead Shark, _Sphyrna zygaena_
    - Whitefin Hammerhead Shark, _Sphyrna couardi_

## Relationship with humans

Out of the nine species of Hammerhead sharks three are dangerous to humans: the Scalloped Hammerhead shark, the Great hammerhead shark, and the Smooth Hammerhead shark.
The Great and Scalloped are listed as endangered by the International Union for the Conservation of Nature, while the Smalleye Hammerhead shark is listed as vulnerable. This is because of over-fishing for the fins of Hammerhead sharks, which are used in sharkfin soup.
In 2010, 33 attacks were reported, but none of these attacks were fatal.

## Hawaiian culture

In Hawaiian culture, sharks are considered to be gods of the seas, they are also known as _aumakua_, protectors of humans, and cleaners of ocean life. Some of these sharks are believed to be family members who have died and have turned into sharks. But there are some sharks which are known as _niuhi_, or man-eaters. These sharks include Great White Sharks, Tiger sharks, and Bull sharks. The Hammerhead sharks are known as _mano kihikihi_, they are not considered as man-eaters or _niuhi_, but are considered one of the most respected sharks in the oceans, an _aumakua_. Many Hawaiians believe that they have an _aumakua_ which watches over them and protects them from the _niuhi_.

## References

- Hammerhead Sharks
- National Geographic-Hammerhead Sharks
- Marine Parks-Hammerhead Sharks