Hammerhead Shark - Description

Description

The nine known species range from 0.9 to 6 m (3.0 to 20 ft) long and weigh from 3 to 580 kg (6.6 to 1,300 lb). Although several hammerhead species are quite large, these are more slender and streamlined compared to other large sharks, which undoubtedly increase their speed and manuverability in the water. They are usually light gray and have a greenish tint to them. Their bellies are white which allows them to be close to the bottom of the ocean and blend in to sneak up on their prey. Their heads have lateral projections which give them a hammer-like shape.

It was determined recently that the hammer-like shape of the head may have evolved (at least in part) to enhance the animal's vision. The positioning of the eyes, mounted on the sides of the shark's distinctive hammer head give the shark good 360-degree vision in the vertical plane, meaning they can see above and below them at all times. The shape of the head was previously thought to help the shark find food, aiding in close-quarters maneuverability and allowing sharp turning movement without losing stability. However, it has been found that the unusual structure of its vertebrae was instrumental in making the turns correctly, more often than the shape of its head, though it would also shift and provide lift. From what is known about the Winghead shark, it would appear that the shape of the hammer-head has to do with an evolved sensory function. Like all sharks, hammerheads have electroreceptory sensory pores called ampullae of Lorenzini. By distributing the receptors over a wider area, hammerheads can sweep for prey more effectively.

Hammerheads have disproportionately small mouths and seem to do a lot of bottom-hunting. They are also known to form schools during the day, sometimes in groups of over 100. In the evening, like other sharks, they become solitary hunters.