FaunaHub

Hammerhead Shark (family Sphyrnidae)

Marine fishSharkPredator

Great hammerhead shark (Sphyrna mokarran) near the seabed at Bimini, Bahamas.

Great hammerhead shark (Sphyrna mokarran), Bimini, Bahamas.

Image: N.E.Youness, CC BY-SA 4.0, via Wikimedia Commons.

Overview

Hammerhead sharks (family Sphyrnidae) are instantly recognisable by their wide, flattened, hammer-shaped head, known as a cephalofoil. There are several species, from small bonnetheads to the large and powerful great hammerhead (Sphyrna mokarran), used here as a reference. The distinctive head is thought to improve manoeuvrability and to spread the shark's sensory organs across a wider area.

Hammerheads are active predators of warm coastal and open seas, and some species form large schools — an unusual behaviour for sharks.

Conservation note: several hammerhead species, including the great and scalloped hammerheads, are of serious conservation concern, heavily affected by fishing and the fin trade. Verify a particular species' status at iucnredlist.org and NOAA Fisheries.

Habitat & Range

Hammerheads live in warm temperate and tropical seas worldwide, in coastal waters, over reefs and continental shelves, and in the open ocean depending on the species. Some undertake seasonal migrations and gather at particular seamounts and islands.

Diet

Hammerheads are carnivores that feed on fish, cephalopods, and crustaceans; the great hammerhead in particular is a specialist hunter of rays and skates, sometimes using its broad head to pin prey against the seabed. Their wide-set senses help them detect prey hidden in the sand.

Behavior

The cephalofoil gives hammerheads a wide spacing of eyes and of the electrically sensitive organs (ampullae of Lorenzini) used to detect prey, which may help them sweep the seafloor for hidden animals. Unusually, some hammerhead species form large daytime schools, while hunting more individually at night. Most are not considered a significant danger to people.

Human Interaction & Conservation

Hammerheads are rarely involved in incidents with humans, but they are under heavy pressure from targeted fishing and bycatch, especially for their fins; as a result several species have declined sharply and are protected in a growing number of places. For current, species-specific status, consult NOAA Fisheries and the IUCN Red List.

More photos of the hammerhead shark

Great hammerhead shark showing its wide, flattened head.

Great hammerhead shark (Sphyrna mokarran).

Image: Gary J. Wood from Toronto, ON, Canada, CC BY-SA 2.0, via Wikimedia Commons.

Frequently Asked Questions — Hammerhead Shark

Why do hammerhead sharks have such a strange head?
The wide, flattened head — the cephalofoil — spreads the shark's eyes and electrosensory organs over a broader area, which is thought to improve its ability to detect prey (including animals hidden in sand) and to aid manoeuvrability. The exact mix of benefits is still studied.
Are hammerhead sharks dangerous to people?
Generally no. Hammerheads are rarely involved in bites on humans and are not considered a significant danger. The more pressing issue is the threat people pose to hammerheads through fishing and the fin trade.
What do hammerhead sharks eat?
They eat fish, squid and octopus, and crustaceans; the large great hammerhead is a specialist predator of rays and skates and may use its head to pin prey to the seabed.
Do hammerhead sharks really swim in schools?
Some do. Certain hammerhead species, such as the scalloped hammerhead, are known to gather in large schools during the day at particular sites, which is unusual among sharks, while hunting more on their own at night.

Sources and further reading

Authoritative wildlife references used for general educational context. Conservation status should always be verified against current IUCN Red List data. External links open in a new tab.