Hammerhead Shark

Hammerhead Shark at a glance

Need to know

• Hammerhead sharks are easily identified by the unique T-shaped hammer (cephalofoil) of their heads, which gives them superior sensory perception.
• Some hammerhead species form huge migratory schools during the day, especially around seamounts and islands.
• They use their wide heads to pin down stingrays, one of their favorite prey items.
• Many hammerhead species have suffered steep population declines due to demand for their fins and bycatch.
• The great hammerhead is the world's largest hammerhead species and can grow over 6 meters long.
• Bonnethead sharks are one of the very few shark species known to ingest seagrass as part of their diet.

About the Hammerhead Shark

Hammerhead sharks are an unmistakable group of sharks named for the strange and remarkable shapes of their flattened, hammer-like heads, called cephalofoils. Ranging from the modest bonnethead to the imposing great hammerhead, these sharks occupy warm temperate and tropical seas worldwide. Their unique head structure is not just odd-looking: it is packed with electroreceptors and wide-set eyes, enabling incredible sensory advantages when hunting.

Hammerhead sharks prey on a variety of marine life, including fish, squid, octopus, crustaceans, and stingrays. While some species, like the scalloped hammerhead, form impressive schools that can number in the hundreds, others are more solitary. Many hammerheads are endangered or critically endangered due to overfishing, especially for their fins, which are highly prized in the shark fin trade.

Physical characteristics

Size: 1.5 to 6.1 meters long, depending on species. Weight: 18 to 450 kilograms. Lifespan: 25 to 40 years, species-dependent.

• Flattened, hammer- or shovel-shaped cephalofoil head
• Set-wide eyes located at the ends of the head
• Tall, curved dorsal fin (especially in great hammerheads)
• Gray, olive, or brown dorsal coloration with a lighter belly
• Streamlined, robust body with sickle-shaped pectoral fins

Notable species

• Great Hammerhead Shark (Sphyrna mokarran) — Critically Endangered. Coastal warm-temperate and tropical seas, continental shelves, sometimes open ocean Regions: Western Atlantic Ocean, Eastern Atlantic Ocean, Indian Ocean, Pacific Ocean, Gulf of Mexico, Caribbean Sea.
• Scalloped Hammerhead Shark (Sphyrna lewini) — Critically Endangered. Coastal and pelagic, tropical and warm-temperate seas; close to continental shelves and offshore islands Regions: Eastern Pacific Ocean, Western Atlantic Ocean, Eastern Atlantic Ocean, Indian Ocean, Mediterranean Sea, Coral Sea.
• Smooth Hammerhead Shark (Sphyrna zygaena) — Vulnerable. Temperate and tropical coastal areas, usually on continental shelves Regions: North Atlantic Ocean, South Atlantic Ocean, Indian Ocean, Eastern Pacific Ocean, Western Pacific Ocean, Southern Ocean.
• Bonnethead Shark (Sphyrna tiburo) — Least Concern. Shallow coastal waters, bays, estuaries, seagrass beds Regions: Western Atlantic Ocean, Gulf of Mexico, Caribbean Sea, Eastern Pacific Ocean.
• Winghead Shark (Eusphyra blochii) — Endangered. Inshore tropical and subtropical waters, often in estuaries and river mouths Regions: Eastern Indian Ocean, Western Pacific Ocean, Borneo Sea, Coral Sea.

Habitat and range

Original range: Tropical and subtropical shallow coastal waters of the world's oceans; likely originated near continental shelves in Eocene era.

Current distribution: Found across tropical, subtropical, and some warm temperate oceans worldwide, with some species extending into estuaries and brackish waters.

Preferred environments: Continental shelves, Coastal shallows, Coral reefs, Oceanic islands, Estuaries, Open ocean (occasionally, in some species)

Regions: Western Atlantic Ocean, Eastern Atlantic Ocean, Indian Ocean, Pacific Ocean, Gulf of Mexico, Caribbean Sea, Coral Sea, Mediterranean Sea, Southern Ocean, Borneo Sea

Where to see Hammerhead Shark

• Cocos Island (Pacific Ocean) — June to November. Large schools of scalloped hammerheads gather near underwater seamounts
• Galapagos Islands (Pacific Ocean) — December to May. Frequent hammerhead sightings, especially at Darwin and Wolf islands
• Bimini (Western Atlantic Ocean) — December to March. Prime location for seeing great hammerheads in shallow clear waters
• Bahamas (Western Atlantic Ocean) — November to April. Multiple hammerhead species can be observed while diving

Behavior and diet

Diet: Mainly bony fishes, stingrays, other sharks, cephalopods (octopus, squid), and crustaceans; bonnetheads also eat seagrass.

Social structure: Varies by species; some (e.g., scalloped hammerhead) are highly social and form large schools, while others (great hammerhead) are mostly solitary.

Communication: Primarily body language; posturing, swimming displays, and electromagnetic sense are important. May use posture to establish dominance.

• Use the width of their head to pin and trap stingrays on the sea floor
• Schooling behavior in juveniles and some adults, especially at seamounts
• Migration over large distances to breeding or feeding grounds
• Live birth (viviparity) with litter sizes varying among species

Interactions with other animals

• Stingrays (prey): Hammerheads are highly specialized at hunting stingrays, which they pin to the bottom with their heads.
• Groupers (competitive): Compete for similar prey on coral reefs and continental shelves.
• Humans (threatened by): Targeted for fins, bycatch, and habitat disruption; subject to protection and study by conservationists.
• Other sharks (including conspecifics) (predatory/competitive): Large hammerheads may prey on smaller sharks, including other hammerheads.

Conservation

IUCN Red List status: Most species: Critically Endangered or Endangered (Great and Scalloped Hammerhead); others Vulnerable or Least Concern (Bonnethead)

Threats

• Overfishing (mainly for fins, but also for meat and oil)
• Bycatch in commercial fisheries
• Destruction or degradation of coastal nursery habitats
• Slow reproductive rate
• Illegal and unregulated fishing

Conservation efforts

• International protections via CITES Appendix II (trade controls)
• Shark sanctuaries (e.g., Bahamas, Palau)
• Ban or restriction of shark finning in many countries
• Improved fisheries management and bycatch mitigation
• Research on population monitoring and migration

How to help

• Support sustainable seafood and avoid shark fin products
• Promote and respect protected marine areas
• Participate in citizen science shark programs
• Raise awareness about the plight of sharks through education
• Advocate for stronger international fishing regulations

Hammerhead Shark facts for kids

Hammerhead sharks are some of the coolest and most unusual sharks in the ocean, with wide flat heads that look like hammers. They use these heads to hunt for food, like stingrays, and see almost everything around them. Many hammerheads live in warm seas all over the world!

• Hammerhead sharks get their name from their funny, hammer-shaped heads.
• Some hammerheads can grow bigger than a car!
• They have eyes on each end of their head so they can see in almost every direction.
• Bonnethead hammerheads like to snack on sea grass, making them part-time plant eaters.
• Baby hammerhead sharks are called pups, and some species have big families with dozens of pups at once!

Did you know? Did you know? Hammerhead sharks use their hammer heads to pin stingrays to the ocean floor so they can eat them more easily!

Watch & learn

• Secrets of the Hammerhead Shark – Ocean's Oddest Predator — National Geographic. This National Geographic documentary explores the extraordinary sensory powers and unique head shape of hammerhead sharks, using underwater footage and scientific insights to reveal their hunting behavior.
• Hammerhead Sharks – The Most Unusual Sharks? — BBC Earth. BBC Earth showcases the evolutionary adaptations and powerful group hunting tactics of hammerhead sharks, with rare footage and expert narration from renowned shark biologists.
• Hammerhead Shark Schooling – The Giant Gathering — Smithsonian Channel. Smithsonian Channel highlights the annual gatherings of hundreds of hammerhead sharks, capturing their social behavior and the underwater world of the Galápagos, where this species congregates in dramatic displays.
• Into the Wild: Hammerhead Sharks in Their Habitat — PBS Nature. PBS Nature dives deep into the life cycle, migration, and conservation challenges facing hammerhead sharks, featuring remote camera footage and interviews with marine researchers.
• The Science of Hammerhead Sharks – Senses and Survival — Nat Geo WILD. A focused exploration by Nat Geo WILD into how hammerhead sharks use their unique head structure to hunt, sense prey, and survive in competitive marine environments, supported by high-definition scientific visuals.