Animal of the Month
February 2017

Name: Hammerhead Shark


Classification:

Class: Chrondrichthyes
Subclass: Elasmobranchii
Superorder: Selachimorpha
Order: Carcharhiniformes
Family: Sphyrnidae
Genus: Sphyrna
Number of Species: 8-10


Size: 13-20 feet long
Weight: 500-1,000 lbs


Characteristics: Long body, pectoral fins, large dorsal fin and tail, t-shaped "hammer" head.
Color(s): Grey-brown or olive green, with white underbellies
Behavior: Migratory
Preferred Habitat: Deeper water
Range: Coastal warm temperate and tropical waters near Central America, the Caribbean, South America, Africa, the southern Mediterranean, Southern Asia and Northern Australia. Also pockets of the Pacific Ocean.
Diet: Primarily stingrays, sometimes also crabs, lobsters, other fish, squid, octopi and even other sharks!
Lifespan: 20-30 years in the wild, captivity N/A


Status: Some species are least concerned or near threatened. Some are vulnerable. Some are not formally evaluated. Some are endangered.


Set apart from other shark species by its bizarre head, the hammerhead shark is one of the most successful predators in the ocean. Sharks have existed on Earth for about 450 million years. The hammerhead however is the newest member of the shark family, having lived for only about 20 million years. Hammerhead sharks can be found in warm and temperate waters across the world, especially in costal areas. They prefer deep water, though sometimes they will come into more shallow areas.


The "hammer head" of the hammerhead shark is known as a cephalofoil. This may look strange, but it's actually an ingenious evolutionary adaptation that has a variety of uses. Whereas most sharks have their eyes close together, hammerheads have their eyes positioned on either end of their wide cephalofoil. This gives them better depth perception and a wider view of the ocean as they patrol, allowing them to spot prey more easily. The cephalofoil also gives the hammerhead a greater sense of electromagnetic fields than other sharks possess. In addition, the cephalofoil allows the shark to turn in the water more quickly, grants a greater sense of smell, and can also be used as a tool to catch prey. The cephalofoil is essentially a built-in multi-purpose tool!


Depending on whom you ask there are eight-to-ten different species of hammerhead sharks. The largest is the great hammerhead, which reaches up to twenty feet long. Most hammerheads are smaller by comparison. Hammerhead sharks are known to migrate in large numbers to cooler waters during the summer. They prefer to hunt stingrays, and their cephalofoils help them to locate these sand-dwelling creatures. They will also eat crabs, octopi, squid, other fish, and sometimes even other sharks. Hammerhead sharks are viviparous, meaning the shark pups are born live. A hammerhead shark can give birth to between twenty and fifty pups at a time! What is even more amazing is that in some circumstances, female hammerheads are capable of reproducing asexually, meaning they can produce pups without a mate! While this can increase hammerhead numbers, it reduces the genetic diversity and makes them more prone to diseases.


Though most hammerheads are considered non-threatening to humans, there are some species that are dangerous. It is important to understand that despite their aggressive tendencies, hammerhead attacks on humans are very rare. Every year humans kill far more sharks than sharks kill humans. Sharks, including hammerheads, are not savage man-eaters, they are merely misunderstood carnivores that are important to the health of the ocean. Sharks keep fish populations in check, and they keep genetic diversity strong by preying on weaker fish. Sharks are not menaces to the oceans; rather they help to regulate them.


Some hammerhead species are rated as Least Concern or are not formally evaluated. However, several species are vulnerable, or even endangered. This is largely due to overfishing for their fins. Shark fins are a delicacy in China, where they are made into shark fin soup. They are obtained in a process called shark finning, where sharks are captured, their fins are cut off and the sharks are thrown back into the ocean. Without their fins the sharks cannot swim and process oxygen, thus they suffocate. Hammerhead fins are especially prized for shark fin soup. What's more, hammerhead numbers are also greatly harmed by commercial bycatch around the world.


Though hammerheads are threatened, there is still hope to preserve them. Check out these awesome organizations that work to protect all sharks, including hammerheads:

Bite-Back - A UK organization dedicated to protecting sharks and other marine species.
http://www.bite-back.com

Shark Savers - An organization founded by passionate scuba divers, dedicated to protecting sharks and manta rays.
http://www.sharksavers.org/en/home/

Project AWARE - A campaign run by PADI (Professional Association of Diving Instructors), dedicated to protecting sharks and removing ocean debris.

WildAid; Shark Page-An organization dedicated to ending all illegal wildlife trade, including the trade of shark fins.
http://www.wildaid.org/sharks

 

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