A hammerhead shark has a wide head shaped like a hammer, and this wide, hammer-shaped head is called the cephalofoil, with a hammerhead's eyes at the two ends of it.

The wide-set eyes at the ends of a hammerhead's head give it good sight. Binocular means using both eyes together, so in a 2009 study the winghead shark, a hammerhead, had a 48-degree arc in front of it covered by both eyes. The same study found that the scalloped hammerhead has a binocular overlap of 34 degrees. The bonnethead, whose head is more spade than hammer, had a much smaller binocular overlap of 13 degrees.

Why does a hammerhead have this head? A National Science Foundation grant calls the function of the widened head unclear, and the hypotheses, which are proposed explanations, include greater maneuverability and lift. The same grant calls hammerheads one of the most striking examples of evolutionary divergence in form and function.

The great hammerhead is the biggest kind of hammerhead shark, and the front edge of an adult great hammerhead's head is nearly straight. A scalloped hammerhead has a notch in the middle of the front of its head.

A hammerhead eats fish, squid and crustaceans such as crabs, and a great hammerhead favors stingrays, groupers and sea catfishes as food. Scalloped hammerheads use their hammer-like head to pin stingrays to the ocean floor before eating them.

Hammerhead sharks live in warm seas around the world. A great hammerhead lives close to the shore and also far out at sea, although it is often found near reefs and the bottom, in water 1 to 80 meters deep.

Adult scalloped hammerheads dive rapidly and repeatedly from warm surface waters to depths exceeding 800 meters, where the water is as cold as 5 degrees C. One scalloped hammerhead followed for 27 days made more than 76 deep dives at night.

As of November 2026, the IUCN Red List lists the great hammerhead as Critically Endangered, which means it is at very high risk of dying out in the wild. It lists the scalloped hammerhead as Critically Endangered too.

A mother hammerhead gives birth to live pups. A mother scalloped hammerhead carries her pups for 9 to 10 months before they are born, and young scalloped hammerheads swim together in large schools.

Adult scalloped hammerheads form schools in which the sexes are mostly kept apart. Great hammerheads migrate with the seasons, which means they travel from place to place as the seasons change, and the great hammerhead is described as a solitary, nomadic and migratory species. Scalloped hammerheads migrate too, and some travel in large schools heading north for the summer.

Words to know

• binocular: using both eyes
• hypotheses: proposed explanations
• maneuverability: turning skill
• lift: an upward push
• solitary: living alone
• nomadic: wandering