Why Do Hammerhead Sharks Have Flat Heads?Reading time: 2 minutes
Hammerheads are a group made up of nine species of shark in the family Sphyrnidae. These sharks derive their name from their distinctive laterally flattened, hammer-shape heads called cephalofoils. But why have these sharks evolved such an oddly shaped snout? Well no-one is 100 percent sure but there are a number of different theories for the head which hold up well under research.
1. Improves overall maneuverability and agility
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The first theory suggests that, in order to compensate for a smaller pectoral fin compared to other shark species, hammerheads use their cephalofoils to give them lift when swimming, much like an aeroplane wing. Theoretically the fact the cephalofoil is larger than a pectoral fin and further from the sharks centre of gravity should allow for better movement and hydrodynamic lift than a fin centred in the middle of the shark’s body. However, research has indicated that the superb manoeuvring capabilities displayed by hammerheads should perhaps instead be mainly attributed to their extremely flexible bodies which allow them to turn and pivot more easily at greater speeds.
2. Aids ability to hunt and trap prey
Image credit: Steve Hinczynski
Hammerhead sharks favour benthic prey such as stingrays. To lessen the danger involved in capturing a stingray hammerheads have developed a way to hold the prey down with their cephalofoils until they are immobilized. This allows them to feed on the stingray without being impaled by the stingray’s tail spines. However, this is most likely a learned technique and not the main reason for the long cephalofoil.
3. Allows for 360-degree vision on the vertical plane
Image credit: IFL Science
Hammerhead’s eyes are located at the end of the cephalofoil which allows them to have a 360-degree view of the world in the vertical plane due to a wider overlap in binocular vision. This field of view is a distinct advantage for an apex predators when hunting for prey.
4. Enhances electrosensory ability
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In short the wide cephalofoil increases the hammerhead’s ability to sense prey. Sharks have gel-filled pores on their lower jaw and around their face. These pores, known as ampullae of Lorenzini, are used to detect electromagnetic radiation such as the nerve impulses in the muscle of a fish. The wider cephalofoil of the hammerhead shark not only allows them to host more electrosensory pores but it also means they are more spread out allowing them to search and forage a larger area. This is backed by in-field observation of hammerheads showing a disposition to hug the sea floor and search out and locate camouflaged stingrays buried beneath the sand.
No design can be perfect though
Featured image credit: Biodiversity Heritage Library