Great hammerhead

Great hammerheads eat other sea animals.

They love to eat stingrays! They also catch fish and squid. They can find food hiding in the sand.

Great hammerheads are active predators. Their favorite food is stingrays and other rays, when they can find them, but they also eat reef fish, groupers, catfish, squid, crustaceans that live on the seafloor and even other sharks.

One idea scientists have is that a hammerhead may use its wide head to pin its prey down while it feeds. The head is also full of senses for finding prey that is hidden under the sand.

Great hammerheads are active predators of a wide range of animals, from invertebrates to bony fishes and sharks, and are known to prefer stingrays and other batoids when available. Georgia Aquarium lists reef fishes, rays, skates, groupers, sea catfish, squid and bottom-dwelling crustaceans, and the Australian Museum reports cownose rays among their prey. The Florida Museum notes that they are thought to eat their own species when food is scarce.

One theory, described by Georgia Aquarium, is that hammerheads pin prey down with the cephalofoil while biting. The head's electrosensory organs let it locate rays buried in sand at close range.

The great hammerhead has amazing senses.

Its eyes are far apart, so it can see a lot around it. Its head can feel tiny signals from animals hiding in the sand.

With an eye at each end of its wide head, a hammerhead has excellent vision. By turning its eyes and sweeping its head from side to side, it can see almost all the way around itself.

Hammerheads also have a sense people do not have. Tiny jelly-filled pores on the head, called ampullae of Lorenzini, can feel the weak electric signals that living animals give off, even when they are hidden in the sand.

The widely spaced eyes give hammerheads excellent binocular vision, and the Australian Museum describes how rotating the eyes and sweeping the head allows almost 360-degree vision. Highly sensitive nostrils can detect traces of amino acids in the water.

All sharks sense electric fields through jelly-filled ampullae of Lorenzini, which can detect prey at close range, within about 50 centimeters, even when it is buried. Hammerheads have more ampullae than any other group of sharks, and one theory is that the wide lobes of the head give more surface area for them. The same sense may help sharks orient to Earth's magnetic field during long migrations. The Australian Museum adds that hammerheads have the largest and most complex brains of any sharks, which it links to processing this flood of sensory information.

Great hammerheads swim long distances.

Some swim to cooler water in summer. They can sweep their heads from side to side to look all around.

Great hammerheads are strong swimmers that travel long distances, and some move to cooler waters in the summer. They can find prey buried in sand, and they can sweep their wide heads from side to side to see almost all the way around.

Hammerheads very rarely bite people. By 2018, scientists who keep records of shark bites had counted only 17 unprovoked bites by all kinds of hammerhead together, and none was fatal.

The great hammerhead is highly migratory, and some populations move poleward into cooler waters during summer. Hammerheads can sweep the head from side to side to widen their field of view, and their ampullae let them locate prey buried in sand; Georgia Aquarium reports the theory that great hammerheads then pin prey down with the head.

Encounters with people are uncommon. According to the International Shark Attack File, cited by the Florida Museum, by 2018 there had been 17 unprovoked bites with no fatalities for all species of the genus Sphyrna combined, and few can be attributed to the great hammerhead itself because hammerhead species are hard to tell apart. Because of its size and varied diet, the museum advises treating it with respect and caution.

Great hammerheads are in big trouble.

Too many are caught by fishing boats. People are making new rules to protect them, so more can grow up.

The IUCN lists the great hammerhead as critically endangered, at extremely high risk of disappearing from the wild. The main threat is fishing. Many are caught by accident in nets and on long fishing lines, and their large fins are wanted for shark fin soup.

Some countries, including the United States and Australia, and the European Union have banned shark finning, the practice of cutting off a shark's fins and throwing the body back into the sea.

The 2018 global IUCN assessment (published 2019) lists Sphyrna mokarran as Critically Endangered under criteria A2bd, with a decreasing population; the threat it names is fishing and harvesting of aquatic resources. The Florida Museum reports that great hammerheads are taken in gillnets and on longlines and as bycatch in driftnet fisheries, that more than 90 percent of those caught die, and that their large fins are highly sought for the fin trade, sometimes removed illegally at sea without the catch being reported. Georgia Aquarium adds that the species is also taken for meat, liver oil, hides and fishmeal, and for sport.

Because hammerhead species are hard to tell apart in high-seas catches, bycatch data are seldom recorded by species, which makes the true impact hard to measure. The United States, Australia and the European Union have adopted shark-finning bans.