hammerhead sharks quick facts
- There are about 10 kinds of hammerhead shark.
- A hammerhead’s head can sense the electric signals of hidden prey.
- The great hammerhead can grow up to 6 m (20 feet) long.
- Great hammerheads love to eat stingrays.
- A great hammerhead can have 6 to 42 pups at a time.
What is a hammerhead shark?
A hammerhead shark is a shark with a wide, flat head shaped like a hammer or a shovel. Britannica says there are about 10 species of hammerhead, and they are among the most unusual-looking sharks in the sea.
The strange head is called a cephalofoil. It is not just for show: it helps the shark find food, see around it and turn quickly.
Hammerheads live in warm and temperate seas all around the world, usually near coasts and over the shallow edges of continents.
| Hammerheads at a glance | |
|---|---|
| Kinds | about 10 species |
| Smallest | the scalloped bonnethead, about 90 cm (35 inches) |
| Largest | the great hammerhead, up to 6 m (20 feet) |
| Favourite food | fish, squid, crabs and especially stingrays |
| Pups | 6 to 42 at a time (great hammerhead) |
| Lifespan | about 20 to 30 years |
| Status | several species Endangered or Critically Endangered |
Why do hammerheads have hammer-shaped heads?
Scientists think the cephalofoil helps in several ways. Britannica lists better steering, a keener ability to find prey, a wider field of view, and the ability to detect the tiny electric signals given off by other animals.
A hammerhead’s eyes are on the ends of its head, far apart. That lets it see a very wide area around it as it swims.
The underside of the head is covered in tiny pores called the ampullae of Lorenzini. The Florida Museum says these detect the electrical signals that come from the muscles of hidden prey.
By sweeping its wide head over the sand like a metal detector, a hammerhead can find stingrays buried out of sight.
Kinds of hammerhead
Great hammerhead: the biggest. The Florida Museum says it can reach 5.5 to 6 m (18 to 20 feet). The world record, caught off Sarasota, Florida, weighed 450 kg (991 pounds). Its head is straight across the front.
Scalloped hammerhead: named for the wavy front edge of its head. NOAA Fisheries says it grows up to about 3.4 m (11 feet) and 152 kg (335 pounds), and can live up to 30 years.
Bonnethead: a small hammerhead with a rounded, shovel-shaped head. Britannica says the smallest kinds are only about 90 cm (35 inches) long.
Where do hammerheads live?
Hammerheads live in warm tropical and temperate seas worldwide. Britannica says they are usually found near coastlines and over continental shelves, where the sea is fairly shallow.
The Florida Museum says great hammerheads are often found in shallow coastal waters and lagoons, down to about 80 m, but they can also swim far offshore to depths of 300 m.
Many hammerheads migrate with the seasons. Britannica says they move towards the equator in winter and towards the poles in summer, following warm water.
In the Galápagos Islands, in the eastern Pacific, big groups of scalloped hammerheads gather together. Britannica says the Galápagos Marine Reserve protects about 30 kinds of shark, including them.
What do hammerhead sharks eat?
Britannica says hammerheads eat many kinds of fish, squid, octopuses and crustaceans such as crabs, depending on the species.
Bonnetheads have flat teeth for crushing crabs, shrimp and small fish buried in the sand. Britannica says the bonnethead is even an omnivore: it eats seagrass as well.
Big hammerheads have blade-like teeth for catching large fish, squid, smaller sharks and rays. The great hammerhead has a particular taste for stingrays.
Britannica says great hammerheads are often found with stingray barbs stuck in their bodies, showing that they do not let a painful sting put them off.
How a hammerhead catches a stingray
A great hammerhead cruises close to the sea floor, sweeping its head from side to side. When its electric sense picks up a stingray hidden in the sand, it strikes.
Some great hammerheads have been seen using their wide heads to pin a stingray to the sea floor, then turning to bite it.
Hammerhead pups
Hammerheads give birth to live young, called pups, instead of laying eggs.
The Florida Museum says a great hammerhead is pregnant for about 11 months and has 6 to 42 pups at a time, in spring or summer. Females give birth once every two years.
The pups are born able to swim and look after themselves straight away. They often grow up in shallow coastal nursery areas, where they are safer from bigger sharks.
How long do hammerheads live?
The Florida Museum says great hammerheads live about 20 to 30 years. NOAA Fisheries says scalloped hammerheads can live up to 30 years.
Are hammerheads dangerous?
Hammerheads are rarely a danger to people. The Florida Museum says there have been 17 recorded unprovoked attacks by hammerhead sharks, with no deaths.
Like all big wild animals, they should be treated with respect and watched from a safe distance.
Hammerheads in danger
People are a far greater danger to hammerheads than they are to us. Britannica says huge numbers are caught for their fins, which are used in shark fin soup.
In finning, the fins are cut off and the rest of the shark is thrown away. Hammerheads are also caught by accident in nets meant for other fish.
The Florida Museum lists the great hammerhead as Endangered. NOAA Fisheries says some populations of scalloped hammerheads are listed as Endangered or Threatened in the USA, and Britannica calls the scalloped hammerhead critically endangered.
More amazing sharks
Hammerheads are just one of many kinds of shark. Meet a famous hunter in our great white shark facts, or the biggest fish of all in our whale shark facts.
Meet the scalloped hammerhead
The scalloped hammerhead gets its name from the wavy front edge of its head, which looks like the edge of a scallop shell.
NOAA Fisheries says scalloped hammerheads grow up to about 3.4 m (11 feet) long, weigh up to about 152 kg (335 pounds) and live up to 30 years.
They live in warm coastal seas all around the world. NOAA Fisheries says they are found from New Jersey to Brazil, from the Mediterranean Sea to Namibia, from South Africa to Australia, and from southern California to Ecuador and Hawaii.
What a great hammerhead looks like
The Florida Museum says the great hammerhead is dark brown to light grey, or even olive, on top, fading to white or cream underneath.
Its head changes shape as it grows. A young great hammerhead has a curved front edge to its head. An adult’s head is almost straight, with a small notch in the middle.
Its teeth are triangular and strongly serrated, like tiny saw blades, which helps it slice through its prey.
Warm seas and shallow water
The Florida Museum says great hammerheads live in warm waters between about 40° north and 35° south of the equator. In the western Atlantic, they range from North Carolina to Uruguay, including the Gulf of Mexico and the Caribbean.
They usually swim in fairly shallow water near the coast, up to about 80 m (260 feet) deep, over continental shelves and in lagoons. Some populations travel towards cooler waters in summer.
Growing up
Young hammerheads have to watch out. The Florida Museum says larger sharks eat young great hammerheads, but adults have no major predators.
Great hammerheads grow up slowly. In Australian waters, the Florida Museum says males become adults at about 2.25 m (7.4 feet) long, and females at about 2.1 m (6.9 feet). When food is scarce, great hammerheads may even eat other hammerheads.
Laws to protect hammerheads
Many countries now protect hammerheads. NOAA Fisheries says four groups of scalloped hammerheads are protected under the US Endangered Species Act. Two of the groups are listed as Endangered, and two are listed as Threatened.
Scalloped hammerheads are also listed under CITES, an international agreement that controls trade in wild animals and plants. That means their fins cannot be traded between countries without special permits.
Hammerhead teeth
A great hammerhead has a mouth full of sharp teeth. The Florida Museum says it has about 17 teeth on each side of its upper jaw, and 16 or 17 on each side of its lower jaw.
Its teeth are triangular, with jagged edges like a saw. Behind them wait rows of spare teeth, ready to move forward when a front tooth breaks or falls out.
The mouth of a hammerhead is quite small for its size, and it sits under the head. That makes it well placed for grabbing prey from the sea floor, such as stingrays hiding in the sand.
Three things people get wrong
A hammerhead’s head is not just for show. It helps the shark find prey, see widely and turn.
Hammerheads are not a big danger to people. Attacks are rare, and none has been fatal.
Not all hammerheads are huge. The smallest are only about 90 cm long.
Did you know? The bonnethead, a small hammerhead, eats seagrass as well as crabs and shrimp.
Try it
Hold your hands out wide, one on each side of your head. That is roughly where a hammerhead’s eyes are. How much more could you see?
Knowledge check
What is a hammerhead’s head called?
Show answer
A cephalofoil.
What is the great hammerhead’s favourite food?
Show answer
Stingrays.
Frequently asked questions
Why do hammerhead sharks have hammer-shaped heads?
The wide head helps them see a wider area, turn quickly and sense the electric signals of prey buried in the sand.
How big do hammerhead sharks get?
The great hammerhead can grow up to about 6 m (20 feet). The smallest hammerheads, such as the scalloped bonnethead, are only about 90 cm long.
What do hammerhead sharks eat?
Hammerheads eat fish, squid, octopuses and crabs. Great hammerheads especially like stingrays, and bonnetheads even eat seagrass.
Where do hammerhead sharks live?
Hammerheads live in warm and temperate seas worldwide, usually near coasts and over continental shelves. Many migrate with the seasons.
Are hammerhead sharks dangerous to humans?
Rarely. The Florida Museum records 17 unprovoked attacks by hammerhead sharks, and none of them was fatal.
Are hammerhead sharks endangered?
Yes. The great hammerhead is listed as Endangered, and scalloped hammerheads are threatened by fishing for the shark fin trade.
Sources
- Encyclopaedia Britannica: hammerhead shark — species, sizes, the cephalofoil, range, migration, diet, stingray barbs, bonnethead seagrass and threats
- Florida Museum of Natural History: great hammerhead — size, record, range, depth, electric sense, diet, pups, lifespan, attacks and status
- NOAA Fisheries: scalloped hammerhead shark — size, lifespan, range, threats and protection
