Hammerhead sharks are marine predators, immediately recognizable by their distinctive head shape. Found in tropical and temperate coastal waters across the globe, these active hunters play an important role in marine ecosystems.
The Hammerhead’s Distinctive Head
The flattened, laterally extended head of a hammerhead shark, known as a cephalofoil, is a multi-functional structure. This unique shape enhances their sensory capabilities, particularly electroreception, by spreading out the Ampullae of Lorenzini, gel-filled pores that detect electrical signals. This wider distribution allows hammerheads to sweep a broad area of the seafloor, detecting hidden prey more effectively than sharks with conventional head shapes.
The placement of their eyes at the ends of the cephalofoil provides superior binocular vision and depth perception, offering a panoramic view of their surroundings. While early theories suggested the head improved maneuverability for sharp turns, more recent studies indicate that the shark’s vertebral structure contributes significantly to this agility. The cephalofoil also plays a role in prey manipulation, as larger species have been observed using it to pin down and stun stingrays before consumption.
Where Hammerheads Live and How They Hunt
Hammerhead sharks inhabit tropical and warm temperate waters worldwide, frequently found in coastal areas and along continental shelves. Some species, like the great hammerhead, undertake extensive migrations, traveling over 1,200 kilometers. While many hammerhead species are solitary predators at night, some, such as scalloped hammerheads, are known to form large schools during the day, particularly around seamounts and oceanic islands.
As active predators, hammerheads eat a varied diet including fish, cephalopods (like squid and octopus), and crustaceans (such as crabs and shrimp). They prefer stingrays, which often hide by burying themselves under sand. Hammerheads employ a distinctive hunting technique by sweeping their cephalofoil over the seafloor to detect the faint electrical signals emitted by buried prey. Once a stingray is located, a great hammerhead might use the underside of its head to pin the ray to the seabed, allowing the shark to bite pieces from the ray’s wings.
Life Cycle and Protecting Hammerheads
Hammerhead sharks reproduce through viviparity, meaning they give birth to live young. After a gestation period that can last around 11 months for great hammerheads, litter sizes vary by species. For instance, the great hammerhead can have litters ranging from 6 to 42 pups, while smaller species might have 4 to 14 pups. Pups are born in shallow, nearshore areas that serve as nursery grounds.
Hammerheads are generally shy around humans, but due to their substantial size, larger species like the great hammerhead should be approached with caution. Many hammerhead species face significant threats, with several classified as Critically Endangered, Endangered, or Vulnerable by the IUCN Red List. The primary threat to these sharks is overfishing, particularly for their fins, which are highly valued in international markets for shark fin soup. Their slow growth rates and relatively low reproductive output make them especially susceptible to overexploitation, hindering population recovery even with conservation efforts.