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Great Hammerhead Shark (Sphyrna mokarran)

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Great Hammerhead Shark Image / Stephen Frink, Getty Images

Great Hammerhead Shark

Stephen Frink, Getty Images

The great hammerhead shark (Sphyrna mokarran) is the largest of the 9 species of hammerhead sharks - species that all have unique hammer or shovel-shaped heads.

Description:

The great hammerhead can reach a maximum length of about 20 feet, but their average length is about 12 feet. Their maximum length is about 990 pounds. They have a grayish-brown to light gray back, and white underside.

Great hammerhead sharks have a notch in the center of their head, which is known as a cephalofoil. The cephalofoil has a gentle curve in juvenile sharks, but becomes straight as the shark ages. Great hammerhead sharks have a very tall, curved first dorsal fin and a smaller second dorsal fin. They have 5 gill slits.

Classification:

  • Kingdom: Animalia
  • Phylum: Chordata
  • Subphylum: Gnathostomata
  • Superclass: Pisces
  • Class: Elasmobranchii
  • Subclass: Neoselachii
  • Infraclass: Selachii
  • Superorder: Galeomorphi
  • Order: Carcharhiniformes
  • Family: Sphyrnidae
  • Genus: Sphyrna
  • Species: mokarran

Habitat and Distribution:

Great hammerhead sharks live in warm temperate and tropical waters in the Atlantic, Pacific and Indian Oceans, Mediterranean and Black Seas, and Arabian Gulf. They undertake seasonal migrations to cooler waters in the summer.

Great hammerheads may be found in both nearshore and offshore waters, over continental shelves, near islands, and near coral reefs.

Feeding:

Hammerheads use their cephalofoils for detection of prey using their electro-reception system, which allows them detect their prey by electrical fields.

Great hammerhead sharks primarily feed at dusk and eat stingrays, invertebrates, and fish, including even other great hammerheads.

Their favorite prey is rays, which they pin down using their heads. They then bite at the ray's wings to immobilize them, and eat the entire ray, including the tail spine.

Reproduction:

Great hammerhead sharks may mate at the surface, which is unusual behavior for a shark. During mating, the male transfers sperm to the female via his claspers. Great hammerhead sharks are viviparous (give birth to live young). The gestation period for a female shark is about 11 months, and 6-42 pups are born live. The pups are about 2 feet long at birth.

Shark Attacks:

Hammerhead sharks are generally not dangerous to humans, but great hammerheads should be avoided due to their size.

Hammerhead sharks in general are listed by the International Shark Attack File #8 on its list of species responsible for shark attacks from the years 1580 to 2011. During this time, hammerheads were responsible for 17 non-fatal, unprovoked attacks and 20 fatal, provoked attacks.

Conservation:

Great hammerheads are listed as endangered by the IUCN Red List due to their slow reproduction rate, high bycatch mortality and harvest in shark finning operations. The IUCN encourages implementation of shark finning bans to protect this species.

References and Further Information:

  1. About.com
  2. Education
  3. Marine Life
  4. Sharks
  5. Shark Species Profiles
  6. Great Hammerhead Shark Profile

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