Great hammerhead

What it is

This shark possesses a streamlined body topped by a distinctive head shape called a cephalofoil. The front edge of this structure is nearly straight, setting it apart from other hammerheads. Adults display dark brown or olive upper surfaces that fade to white underneath. Their first dorsal fin stands tall and curved like a sickle, while pelvic fins show strong concave rear edges. Individuals typically measure around four and a half metres, though some females exceed six metres. The skin features diamond-shaped scales with ridges that vary by size.

Where it lives

Populations inhabit tropical oceans across the globe, spanning latitudes from forty degrees north to thirty-seven degrees south. They appear in the Atlantic from North Carolina to Uruguay and Morocco to Senegal. Pacific ranges extend from Baja California to Peru and Ryukyu Islands to Australia. Habitat choices include coral reefs, island terraces, and continental shelves. Depths range from shallow inshore waters under one metre to eighty metres offshore. Seasonal migrations move groups toward higher latitudes during summer months.

How it lives

These sharks act as solitary apex predators, hunting primarily at dawn or dusk. They target stingrays using electroreceptors on their head to detect buried prey. A unique hunting technique involves striking rays with the cephalofoil to immobilize them before biting. Diets also include crabs, squid, jacks, and smaller sharks. Juveniles face predation from bull sharks, while adults encounter no major threats except killer whales. They sometimes swim on their side to reduce drag and save energy.

Breeding and life cycle

Reproduction occurs via viviparity, where embryos develop inside the mother with a placental-like connection after yolk depletion. Mating happens near the surface rather than on the seabed. Females breed every two years, carrying young for eleven months. Litters contain six to fifty-five pups, measuring fifty to seventy centimetres at birth. Young sharks possess rounded head margins distinct from adult straight edges. Sexual maturity arrives at lengths between two and three metres.

Fish and people

Fishermen capture these sharks using longlines, nets, and trawls throughout tropical regions. Their fins hold high value in Asian markets for shark fin soup, driving significant fishing pressure. Meat remains rarely consumed, though skin and liver oil find commercial use. Accidental catches result in mortality rates exceeding ninety percent in some areas. Recreational harvesting bans exist in Queensland, while other Australian jurisdictions permit targeting. Interactions with divers are generally shy, despite historical reputations for aggression.

Status and threats

The species faces critical endangerment due to slow reproduction and heavy fishing exploitation. Populations have dropped significantly since the nineteen nineties, particularly in the northwest Atlantic and Gulf of Mexico. Illegal longline operations in the southwestern Indian Ocean further threaten numbers. Catch rates in the Indian Ocean fell by seventy-three percent between seventeen hundred and seventy-eight and two thousand and three. Conservation efforts struggle because fisheries often group this species with others in catch reports.

Relatives and look-alikes

Genetic analysis places the great hammerhead in a basal clade alongside the smooth hammerhead. This challenges older views that large heads evolved gradually. The scalloped hammerhead shares similar habitats but differs in head margin curvature and pelvic fin shape. Historical fossil teeth from Cuba and Florida indicate ancient presence. The name Sphyrna tudes was previously misapplied to smalleye hammerheads before molecular studies clarified identities.

Questions people ask about Great hammerhead

Good reading and sources

• Extinction: 'Time is running out' to save sharks and raysBBC, Article

• Great hammerhead on WikipediaEncyclopedia
• More photos on Wikimedia CommonsPhotos
• Wikidata recordOpen data