Top 10 Interesting Facts About Hammerhead Sharks

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Top 10 Interesting Facts About Hammerhead Sharks

Hammerhead_Shark
Credit: Alan Studley/Nature’s Best Photography

Most sharks are hard to distinguish from each other, but not the hammerhead. One look at it and you know just what shark you’re dealing with. Its head has an interesting, if not weird, shape, after all, and that’s not the only thing interesting about it. Here are the top ten interesting facts about hammerhead sharks.


1. There are nine known species of hammerhead shark.

Sphyrnidae_distribution_map
Distribution map of hammerhead sharks (Family: Sphyrnidae) by Canuckguy, PD image.

When you think of a hammerhead shark, you’re probably thinking about just one shark, but the truth is that there are at least nine different species of hammerhead sharks. These are: the great hammerhead shark, the smooth hammerhead shark, the scalloped hammerhead shark, the whitefin hammerhead shark, the smalleye hammerhead shark, the bonnethead, the scalloped bonnethead, the scoophead and the winghead shark.

These hammerhead sharks can be found all over the world in warm waters — in reefs, coastal waters, continental shelves and open oceans.




2. The great hammerhead shark is the largest of the hammerhead sharks.

Great_hammerhead_shark
Great hammerhead by Albert kok cc4.0

Of all the species of hammerhead shark, the great hammerhead shark is the largest, with the longest recorded reaching 20 feet long – that’s longer than most pickup trucks! It can also weigh over 1000 pounds. On average, though, great hammerhead sharks are about 11 feet long and weigh around 500 pounds. The females are larger than the males. However, the males mature earlier.


3. The unique shape of the hammerhead shark’s head allows it to see better than other sharks.

hammerhead_shark_vision
Hammerhead Shark Vision. Image credit: zanthrax-dot-nl, cc2.0

Why does the hammerhead shark have such a weird-shaped head? What good can such a head be for? Scientists believe that the hammerhead shark’s head allows it to see well. Indeed, rather than using each eye independently like most fishes do, the hammerhead shark uses both eyes together to see just like we do. The wider apart the eyes are, the greater the range of the vision.

Hammerhead sharks have a 360-degree range of vision. This means that they can see all around them at all times, whether in front of them, behind them, above them or below them, which helps during hunting and also helps them get away from predators.


4. Three species of hammerhead sharks do not have a hammer-shaped head.

Bonnethead_Shark
Bonnethead shark (Sphyrna tiburo) at the Texas State Aquarium. Image credit: Matt Howry cc2.0

The head of a hammerhead shark is called the cephalofoil, which varies in shape and size among the different species of hammerhead shark. The great hammerhead shark has a broad, flat head with a notch in the center. The scalloped hammerhead has an arched head with matching notches on either side. The smooth hammerhead has no notches. The winghead shark has a particularly wide head, which can be half its total length.

Most of them have pretty much similar-looking heads, though, except for the scoophead, the bonnethead and the scalloped bonnethead. Their heads look more like the end of a shovel than a hammer.


5. Some hammerhead sharks live in schools.

Scalloped_hammerhead_sharks_Sphyrna_lewini_school
Scalloped hammerhead sharks (Sphyrna lewini) school. Image credit: Ryan Espanto, cc2.0

Most sharks are solitary, which means they live and hunt alone. Some hammerhead sharks, however, like the scalloped hammerhead sharks, live and hunt in groups called schools, some of which can be found just beneath the water’s surface. A school of scalloped hammerhead sharks can consist of hundreds of individuals.


6. Hammerhead sharks love to eat stingrays.

Stingray
Stingray by petersbar cc2.0

Stingrays are by no means an easy meal, but hammerhead sharks do not mind the danger. Patiently, they swim close to the ocean floor in search of stingrays that are buried in the sand, and when they find one, they sneak up to it, pinning it down with their larger head before it can sting, and eating it bite by bite while it is still alive.

Aside from stingrays, hammerhead sharks will also eat fish, squid, octopuses and crustaceans. Sometimes they also eat other sharks. The great hammerhead shark, in particular, is known for eating smaller sharks of its own kind, even its own young if food is hard to find.


7. Female hammerhead sharks give birth.

viviparous_sharks_hammerhead_shark
Viviparous Sharks. A hammerhead female with 15 well-developed pups which were removed from the uterus. Image credit: D. Perrine

That’s right. Hammerhead sharks do not lay eggs. Instead, they have babies, which are called pups.

Once a year, when it is time to mate, the male hammerhead shark approaches the female and keeps biting her until she agrees to mate. Afterward, the female becomes pregnant for a few weeks to up to several months, depending on the species. As with other animals, larger sharks are pregnant longer because they have more babies, while smaller sharks have fewer pups and are only pregnant for a few weeks. Medium-sized hammerhead sharks have twelve to fifteen pups, while the great hammerhead shark can have as many as fifty-five. As soon as they are born, the pups can swim and hunt on their own, and they should since they are left alone without any care from either their mother or father.


8. Young hammerhead sharks like to get a nice tan.

hammerhead-shark
Image credit: goranmx, PD Image.

You can tell old hammerhead sharks from young hammerhead sharks not just by the size of their heads — younger sharks have smaller heads, of course — but also from their tan. Yup, young hammerhead sharks get tans because they like to stay closer to the water’s surface. Sometimes, they can even turn black. And guess what? They don’t need to worry about getting sunburned. Indeed, their skin doesn’t get damaged in any way, which is why scientists are currently studying them to find new ways of preventing skin disease in humans.


9. Hammerhead sharks rarely attack humans.

Smoot_Hammerhead_Shark
Smooth Hammerhead, Shark Sphyrna zygaena. Sea of Cortez, La Paz, Baja California Sur, Mexico. Image credit: elasmodiver, cc4.0

Scream “Shark!” and people will immediately swim or run to shore, but the truth is, of the hundreds of species of sharks in the ocean, only a few species are known to attack humans and only four are considered major threats — the great white, the tiger shark, the bull shark and the oceanic whitetip. Of the hammerhead sharks, only three species have been to attack humans — the great hammerhead shark, the smooth hammerhead shark and the scalloped hammerhead shark — and only 17 times in the past 450 years. Also, none of those attacks were serious enough to be fatal.




10. Four species of hammerhead sharks are currently threatened by extinction.

Shark_fins
Fresh shark fins drying on sidewalk at Hong Kong. Image credit: Cloneofsnake, cc2.0

Hammerhead sharks are in even more danger from humans than we are from them. Of the nine species, two are classified as Endangered, which means their population has already declined by so much in just a short period of time, and two are classified as Vulnerable, which means their population is declining. These are the great hammerhead shark, the scalloped hammerhead shark, the smooth hammerhead shark and the smalleye hammerhead shark.

In Africa, the great hammerhead shark is already considered Critically Endangered.

Why? These hammerhead sharks, which are the larger species, are regularly caught in trawls and fixed bottom nets. Their fins are used to make shark fin soup, an expensive delicacy in Asia. Their skin is used for leather and their liver oil for vitamins. The other parts are usually thrown away.


Hammerhead Shark Videos

The YouTube video below contains a playlist of 3 videos about hammerhead Sharks. The list of videos featured is underneath.

The Playlist:

  1. Hammerhead shark evolution – BBC. A look at how the hammerhead’s strange head came about.
  2. Gatherings of Hammerhead sharks in Costa Rica – BBC Earth. Kim Holland discusses the huge crowds of Hammerhead sharks seen in this BBC footage.
  3. World’s Deadliest : Hammerhead Sharks by NatGeoWild. More discussion on the hammerhead shark.

Sources:

http://en.wikipedia.org/wiki/Hammerhead_shark
http://www.sharks-world.com/hammerhead_shark/
http://animals.howstuffworks.com/fish/sharks/hammerhead-shark2.htm
http://animals.nationalgeographic.com/animals/fish/hammerhead-shark/

To view the complete list of sources, click here…

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