WHAT ARE HAMMERHEADS?
Hammerhead sharks are among the ocean’s most fascinating predators - instantly recognisable by their wide, hammer-shaped heads. But what’s the purpose of that unusual shape?
Scalloped hammerhead (Sphyrna lewini) - By David R; CC BY-NC 4.0
Hammerheads are sharks of the family Sphyrnidae, and there are ten known species, from the small bonnethead (Sphyrna tiburo) to the massive great hammerhead (Sphyrna mokarran). All ten species are recognisable by their wide flattened head, called a cephalofoil.
The cephalofoil isn’t just for show, it provides hammerheads with three major advantages:
Panoramic vision and powerful smell
The wide placement of their eyes and nostrils gives hammerheads an almost 360° field of view and enhanced smell detection (stereo-olfaction). This allows them to scan their surroundings more effectively while searching for prey.
Supercharged electroreception
The cephalofoil also holds special sensory organs called ampullae of Lorenzini, which detect tiny electrical fields produced by other animals. These sensory organs allow hammerheads to locate prey more precisely, like finding stingrays buried under sand or fish hiding in murky water.
Exceptional manoeuvrability
The broad cephalofoil acts like a hydrodynamic wing, improving stability and steering. The shape of the cephalofoil helps hammerheads make sharp, agile turns while chasing prey or swimming in strong currents.
Great hammerhead (Sphyrna mokarran) - By katradd7777; CC BY-NC 4.0
Despite the cephalofoil offering many advantages, it also comes with drawbacks. Its broad shape makes hammerheads more likely to become entangled in fishing nets, and their tall, distinctive dorsal fins are highly valued in the fin trade. Even when released, many hammerheads struggle to survive due to stress and injury after capture.
Sadly, hammerhead sharks are now among the most threatened shark groups in the world. Overfishing, bycatch, and the demand for fins have driven their populations to steep declines. Because they grow slowly and produce few offspring, recovery is especially difficult. That’s why initiatives like Hammerhead Hub are vital for understanding and generate the science we need to protect them.
Fun fact: Hammerheads can tan! When they spend time near the surface, their skin darkens, just like us.
Watch: underwater footage from our BRUVS surveys showing scalloped hammerheads in different habitats.