Hammerhead Sharks: Advanced Evolutionary Creatures

Get to know this ferocious creature that spans the world's waters. Learn its secrets and find out why the hammerhead shark is an effective hunter.

Hammerhead sharks are aggressive and effective hunters. These creatures are carnivores, feeding on squids, octopuses, smaller fishes, and crustaceans. There are nine known species of hammerhead sharks today and all have hammer-like projections on each side of the head, hence the name. Its eyes and nostrils are on the tips of these extensions.

The hammer provides the shark with the needed lift, as these species are negatively buoyant. It also allows for correct turns. Hammerhead sharks range from 3 to 20 feet long and can weigh up to 1,000 pounds. Of the nine species identified, the scalloped, smooth and the great hammerheads are most dangerous to humans. The hammerhead sharks are not known to actively seek out human prey but will attack when provoked.

The hammerhead sharks appear to be closely related to a mid-Tertiary period evolution, the carcharhinid shark. The hammerhead's teeth resemble that of some carcharhinids but determining the hammerhead's first appearance is difficult. Geneticist Andrew Martin studied all hammerhead species and concluded the winghead shark was where the hammerhead species began.

As in most sharks, hammerheads have sensory receptors that it uses to hunt for preys. The hammerhead's receptors are distributed in a wide area. With eyes set at the tips of its hammer-like extension, have wider visual fields and longer ranges than most sharks. This greatly improves its prey-sweeping ability.

The projection on its head also provides the hammerhead shark wider nasal tracts that allow hammerheads to spot preys or particles in the water about ten times as effective as other sharks. Hearing is highly developed in hammerhead sharks. Hammerheads are able hear sounds in the entire range humans can. A hammerhead's ear controls its balance and enables it to detect motion. It picks up low frequency vibrations much like sounds from wounded fish. Despite these abilities, hammerhead sharks have small mouths. Drawn to schools of over a hundred in daylight, these ferocious-looking creatures are lone hunters at night.

Hammerhead sharks reproduce once a year. On average, each reproductive cycle results to anywhere from 20 to 40 pups. Male sharks violently force females into coupling. Embryo develops in a placenta and is fed through an umbilical cord and stays there from 10 months to a year. Once born, young hammerheads are left to fend for themselves.
In May 2007, scientists astounded the world with the discovery that hammerhead sharks are capable of asexual reproduction.

Hammerheads can be found in temperate and tropical waters around the world. Summers means mass migrations for hammerheads as they head for cooler waters. They appear olive-green or gray-brown on top and have off-white undersides.

Today, both the great and the scalloped hammerhead sharks are listed as endangered species. Over-fishing to fill the continued demand for its fins, an expensive delicacy, has vastly decreased the scalloped hammerhead's population. Scientists have voiced their concerns about these great creatures and the Conservation Union has classified them as endangered species.

Sharks are great ocean creatures that are of advanced evolutionary stage. Scientists continue to study these ferocious giants and recent reports indicate a probably tenth species of the hammerhead sharks. This probable additional species springs from the discovery that the scalloped hammerheads may actually be two species - the result of more genetic testing rather than a discovery of new physical characteristic.