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Interesting Facts about Hammerhead Sharks
[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Read more about the fascinating and unique interesting facts about hammerhead sharks in our oceans in our marine life blogs. For more information on other marine life, or life on liveaboards read our other informative blogs such as Behind the Scenes as a Cruise Director by our guest blogger and former cruise director in Palau and Egypt.[/vc_column_text][vc_separator][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]
Hammerhead Shark -family Sphyrnidae
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Hammerhead sharks are easily the most easily recognised species with its distinctive evolution of the cephalofoils off the sides of the heads. Some of the best places to see hammerheads are in Costa Rica Cocos Island, Galapagos and Malpelo Island in Colombia.
This distinctive feature allows 360-degree vision and added manoeuvrability which significantly benefits hunting. The downside is their mouths are comparatively smaller than the rest of their body. And they are abnormally small compared to other species of sharks. They also have a blind spot directly in front of their nose.
Many species are classed as Hammerhead sharks, they are:
Great Hammerhead, Bonnethead, the Scalloped hammerhead, Carolina hammerhead, Scoophead shark, Smalleye hammerhead, Smooth hammerhead, Whitefin hammerhead and the Winghead shark. Read more about these species at the end of the blog.
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Hammerhead sharks can vary in length from 1 to 6m + and weighing in at 3 to 170 kg, the Great Hammerhead being the largest. Colours range from brown to grey, and they have a white, grey or even olive green underside to aid in camouflage. They have a lifespan of 25 to 35 years, but recently this is increasing for some unknown reason.
Like all sharks, they have electroreceptors sensors allowing them to sense electromagnetic pulses from their prey. Their distinctive head shape allows for a wider scanning area making them one of the most deadly predators in the ocean. They can even sense the beating heart of humans from several miles away.
One unusual fact is that hammerheads do actually get a suntan, this is due to the extended time they spend hunting in the shallow waters.
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Feeding and hunting
They are active hunters rather than opportunists and the favourite time is at dusk as the light works best for the hammerheads at this time. The diet is mainly bottom dwellers such as invertebrates, crabs, octopus and bony fish, but they will eat almost anything. They have a preference for stingrays and are even known to be cannibals of other species in the hammerhead family.
Attacks by hammerhead sharks on humans are extremely rare with only 3 of the species every been involved. During the shark dives the trained divers know the signs of when the sharks are becoming agitated and how to deal with them.
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Hammerhead sharks are found in the tropical waters along the coastline and continental shelves, but occasionally in the deep ocean near the surface. They tend to travel solo, but the Scalloped hammerheads can be seen in groups of over 100 individuals. This is thought to be for protection from the opposite sex. Females will attract many males when alone, but in groups, they can select the males. The phenomena can attract many tourists when they congregate like this.
Breeding
Hammerhead sharks are hatching their eggs internally then releasing the pups once they are strong enough, during this time they feed on the yolk of the egg. Usually, the birthing season in during the spring or summer in the northern hemisphere. Somewhere between 6 and 40 pups can be born at any one time depending on the species.
The pups are abandoned on birthing often travel to the warmer water together before separating once they are large enough. But if other hammerheads are in the vicinity, they will remain together for protection.
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The International Union for Conservation of Nature states that the Great and Scalloped hammerheads are listed as endangered. The Smalleye Hammerhead is listed as vulnerable.
Humans are the greatest threat to hammerhead sharks due to overfishing and fining practices. They were added to the Convention on International Trade in Endangered Species of Wild Fauna and Flora that protects endangered species which is the first step to increase the population, hopefully.
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Great Hammerhead - Sphyrna mokarran
The largest of all the hammerhead sharks, reaching 6m but with an average of around 3.5 m. They are found in the Indian, Pacific and Atlantic Oceans, the Mediterranean, Black Seas and Arabian Gulf. The large hammer distinguishes them with a notch in the middle.
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Smooth Hammerhead - Sphyrna zygaena
A large shark reaching up to 4 m in length with a large hammer but no notch. They are found in the northern Canadian waters down the coast of the US to the Caribbean and Hawaii. But they are not limited to the Americas as they are also seen in the western Pacific, around Australia, South America, Europe, and Africa.
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Scalloped Hammerhead - Sphyrna lewini
Also reaching up to 4 m this hammerhead has narrow blades and a notch in the centre and indentations resembling the shell of some scallops which give the shark its name. They are found inshore in deep water in the western Atlantic Ocean, the eastern Atlantic, the Mediterranean Sea, the Pacific Ocean and off of Hawaii. Also the Red Sea, Indian Ocean, and the western Pacific Ocean from Japan down to Australia.
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Scalloped Bonnethead- Sphyrna corona
This is a smaller shark that reaches only about 1m in length, the head is rounder, more like a ballot than a hammer. They have a small area in the eastern Pacific from Mexico to Peru.
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Winghead Shark - Eusphyra blochii
They reach just under 2m in length and have a very large, wing-shaped head with narrow blades.
They favour the shallow, tropical waters of the Indo-West Pacific or the Persian Gulf to the Phillippines or from China to Australia.[/vc_column_text][/vc_column][vc_column width=\"1/3\"][vc_column_text]
Scoophead Shark - Sphyrna media
Reaching a maximum of 1.5m this variety has a broad, mallet-shaped head with shallow indentations. They are found in the Pacific from the Gulf of California to Peru and in the western Atlantic Ocean from Panama to Brazil. The behaviour and biology of this variety is not well known.
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Bonnethead Shark - Sphyrna tiburo
Reaching up to 1.5m they have a narrow, shovel-shaped head. They can be seen in the tropical waters in the eastern Pacific and western Atlantic Oceans.
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Smalleye Hammerhead - Sphyrna tudes
Also a maximum of 1.5m in length they have a broad, arched, mallet-shaped head with a deep indentation in its centre. Found in the eastern coast of South America.
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Whitefin Hammerhead - Sphyrna couardi
One of the larger varieties they reach up to 2.7m in length and have a broad head with narrow blades. They can be found in tropical waters in the eastern Atlantic off the coast of Africa.
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Carolina Hammerhead - Sphyrna gilberti
Almost identical to the Scalloped hammerhead this was found in 2013, they have ten vertebrae fewer than the close relative.
[/vc_column_text][/vc_column][/vc_row][vc_row][vc_column][vc_column_text]Images were provided by Jerry Arriaga @OurOceanImages[/vc_column_text][/vc_column][/vc_row]