Great Hammerhead Shark

Quick Take

• Great hammerheads routinely hunt venomous stingrays, and scientists have found something lodged in their mouths that suggests something remarkable about how their bodies handle the venom. Stingray hunting details →
• The hammer-shaped head looks bizarre, but it gives this shark a sensory advantage over its prey that most people would never guess. Sensory organs explained →
• Despite its reputation as an aggressive apex predator, the great hammerhead's attack history with humans tells a very different story than you'd expect. Human attack history →
• This shark abandons its pups at birth, though the location it chooses to do so turns out to be oddly strategic. Pup birth locations →

The great hammerhead shark (Sphyrna mokarran) is the largest of all hammerhead sharks and one of the ocean’s most distinctive predators. Instantly recognizable by its broad, hammer-shaped head, this powerful hunter uses exceptional vision and specialized sensory organs to locate prey hidden beneath the seafloor. Found in tropical and warm temperate waters around the world, the great hammerhead is now listed as Critically Endangered after decades of population declines driven primarily by overfishing.

Great Hammerhead Shark Facts

• The longest great hammerhead shark measured 20 feet, and the heaviest weighed a whopping 1,280 pounds!
• Great hammerhead sharks are most commonly found in shallow coastal waters at depths up to around 328 feet (100 meters). However, they have been found at greater depths, occasionally exceeding 984 feet (300 meters).
• Great hammerhead sharks love to eat stingrays and have been found with their stingers protruding from their mouths, suggesting they are immune to stingray venom.
• The great hammerhead shark’s gestation period lasts for 11 months, and she gives birth to between 13 and 42 pups, though litters of up to 55 pups have been recorded.

The Story Behind Its Scientific Name

The great hammerhead shark’s scientific name is Sphyrna mokarran, a mixture of Greek and Arabic meaning “great hammer.” A German naturalist and explorer, Wilhelm Peter Eduard Simon Rüppell, first discovered the species in 1837. Following his two major expeditions to northern Africa beginning in 1817, he became director of the Senckenberg Natural History Society, a role he held for almost 30 years. On his second expedition beginning in 1830, near Eritrea on the Red Sea, Wilhelm witnessed a great hammerhead shark stranded on a sandbank while trying to catch its prey. He noticed that it differed from the four species already documented by French zoologist Achille Valenciennes. So, Wilhelm gave it the Arabic name mokarran, which means “great.”

Behavior

The great hammerhead is a solitary predator but has been known to swim in schools from time to time. It is an aggressive hunter and will attack if threatened. Although they do not actively seek out humans, attacks have been recorded.

However, only 16 attacks have been documented between 1900 and the present, and none resulted in death. The majority of these attacks have occurred off the coast of Florida, California, and Australia. However, great hammerheads are rare in California waters.

Appearance

Because their eyes sit on the edge of their mallet-shaped heads, they have excellent eyesight and a 360-degree view of their surroundings, making them skilled hunters. They also have a group of sensory organs called the ampullae of Lorenzini, the function of which is to detect electrical fields created by other animals. This aids the great hammerhead in finding its food, especially prey like flounders or stingrays that hide under the sand. See what it looks like swimming in the ocean in the video below:

Habitat

Great hammerhead sharks are found worldwide, mostly in shallow waters over continental shelves and island terraces. However, they also venture out to deeper waters well offshore. They are generally found at depths of 30 to 80 feet but can reach depths of 262 feet. Their favorite habitats are usually continental and insular coral reefs with abundant food.

Diet

The great hammerhead shark is no picky eater; it has a broad diet that includes:

• Stingrays
• Small sharks
• Bony fish
• Crustaceans
• Squid
• Octopus

They utilize their unique sensory function, electroreception, and nearly 360-degree vision to locate their prey and immobilize it so it cannot swim away.

Predators and Threats

Due to the great hammerhead shark’s immense size, it has few known predators. However, bull sharks prey upon the pups, and the adults are hunted and killed by killer whales. Their biggest threat, though, is the human race because severe overfishing has led to the decline of this unique species.

These sharks are targeted because their large pectoral fins are valued in the international shark fin trade, particularly in East Asia. In addition, their habitat is dwindling, and they are listed as critically endangered on IUCN’s Red List.

Interestingly, scientists have documented cannibalism within the species. Though rare, some adults will attack, kill, and eat pups. This behavior has been reported in captivity and inferred from stomach contents in wild specimens.

Reproduction, Babies, and Lifespan

Their reproduction process is similar to that of other sharks, where the male uses his clasper to fertilize the female’s eggs through her cloaca.

Great hammerheads reproduce in a viviparous manner. The mother’s eggs hatch inside the uterus, and she gives live birth to about 6 to 42 pups.

While in the uterus, the pups receive nutrients through an umbilical cord attached to a placenta, which connects near their pectoral fins. The female’s gestation period lasts 11 months; once the pups are born, they are left to fend for themselves. While this doesn’t sound very maternal, the females give birth in bays or estuaries where mangrove forests can shelter and protect the pups. If the pups reach adulthood, their average lifespan is between 20 and 30 years.

Population

No data exists on the great hammerhead’s population size; unfortunately, severe regional declines have been documented, which is why they are listed as critically endangered. Great hammerhead shark populations in the Indian Ocean, Mediterranean Sea, and Atlantic Ocean have significantly decreased. Scientists have concluded that their population has declined by 80% over the last 70 years.