Hammerhead Shark

Hammerhead Shark facts at a glance

What is a group of hammerhead sharks called?

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The hammer-shaped head

The wide, flattened head that gives these sharks their name is called a cephalofoil, and it is more than an odd silhouette. Spacing the eyes far apart gives the shark a broader field of vision, while the underside is packed with electroreceptors called ampullae of Lorenzini that detect the faint electrical signals of buried prey. Sweeping the head from side to side lets a hammerhead scan the seabed like a metal detector. The shape also acts as a hydrofoil, helping the shark bank and turn sharply as it swims.

Hunting and diet

Hammerheads are carnivores that feed on bony fish, squid, octopus, crustaceans and other sharks, but they are best known for hunting stingrays. A hammerhead will pin a ray to the seabed with the edge of its head, then pivot to take bites from the disc. Many individuals seem largely unbothered by the venomous barbs of their prey, and rays recovered from their stomachs are sometimes studded with spines. Larger species hunt alone, cruising close to the bottom where their electrical sense works best.

Size and species

The family Sphyrnidae contains around nine species, and they vary enormously in size. The small bonnethead reaches under a metre, while the great hammerhead can exceed 6 m and weigh in the region of 230 kg, making it one of the largest predatory sharks. The scalloped and smooth hammerheads fall between these extremes. Despite their formidable appearance, hammerheads pose little danger to people, and unprovoked bites are very rare.

Where they live

Hammerheads swim through warm temperate and tropical waters around the world, along coastlines, over continental shelves and out into the open ocean. They are found from shallow lagoons and coral reefs to depths of several hundred metres. Some species, notably the scalloped hammerhead, gather in large schools around seamounts and offshore islands, particularly by day. These aggregations can number in the hundreds and are a famous sight for divers.

Reproduction

Hammerheads give birth to live young rather than laying eggs, nourishing the developing pups through a placenta-like connection inside the mother. Litters range from around a dozen to more than 40 pups depending on the species. The newborns are miniature versions of the adults, with heads that are more rounded at birth and flatten as they grow. Coastal nursery areas in shallow water shelter the young from larger predators during their vulnerable first months.

Why the great hammerhead is Critically Endangered

The great hammerhead is listed as Critically Endangered by the IUCN, and several other hammerhead species are also threatened. Their large fins are highly valued in the shark-fin trade, and the sharks are frequently caught both deliberately and as bycatch in commercial fisheries. Hammerheads are especially vulnerable because they are slow to mature and produce relatively few young. They also suffer very high stress levels when hooked, so many die even when released.

Did you know? Hammerhead Shark facts

• The hammerhead's wide head, called a cephalofoil, spreads its senses far apart.
• This gives hammerheads exceptional 360-degree vertical vision.
• Electroreceptors across the head help detect prey hidden in the sand.
• Some hammerheads form large schools by day, unusual among sharks.
• Great hammerheads are powerful predators of rays, which they pin with the head.
• Several hammerhead species are now endangered from overfishing.

Diet & feeding

Hammerheads prey on fish, cephalopods, crustaceans, and especially rays — great hammerheads are ray specialists, using the broad head to pin prey against the seabed.

Adaptations

• The wide cephalofoil spreads electroreceptors and eyes to improve prey detection. (Compagno 2001)
• Widely spaced eyes provide an exceptional field of view.
• Enhanced electroreception locates rays and other prey buried in sediment.
• A manoeuvrable body lets great hammerheads pin stingrays with the head.

Behaviour & ecology

• Some hammerheads school in large numbers during the day, dispersing to hunt at night.
• Great hammerheads specialise on rays, using the head to trap them.
• They patrol reefs, seamounts, and coastal waters in search of prey.
• Many undertake seasonal migrations.

Communication

• Hammerheads rely on body posture and movement in social and threat contexts.
• Electroreception and other senses dominate prey detection over signalling.
• Schooling behaviour is coordinated by shared cues rather than vocalisation.

Habitat & range

Hammerhead sharks occupy warm coastal and offshore waters worldwide, frequenting reefs, continental shelves, and seamounts.

Ecological role

As mid-to-apex marine predators, hammerheads regulate populations of rays, fish, and cephalopods, helping maintain reef and coastal ecosystem balance.

Conservation status of the Hammerhead Shark

Sources & references

This guide is compiled and reviewed against established zoological and conservation references. Key sources for the Hammerhead Shark:

• IUCN Red List of Threatened Species

  Conservation status (Critically Endangered) reflects the IUCN Red List category for Sphyrnidae.

• Rigby, C. L. et al. (2019). Sphyrna mokarran. IUCN Red List of Threatened Species.

  Status (Critically Endangered) for great hammerhead.

• Compagno, L. J. V. (2001). Sharks of the World. FAO Species Catalogue for Fishery Purposes.

  Taxonomy and biology.

• Froese, R. & Pauly, D. (eds.). FishBase — Sphyrna.

  Size, distribution, and biology.

• Global Animal Guide editorial standards

  How we research, source, review, and update every guide for accuracy.