Of all the curious creatures in our oceans, the Hammerhead Shark must be one of the most mysterious and beautiful. They have baffled scientists, fishermen and myth makers for generations. This is because of their uniquely shaped head and their migrations, which see them gathering in huge shoals.
The Hammerhead Shark, however, is endangered. The Smalleye Hammerhead is considered to be vulnerable. This is due to overfishing. Unfortunately thousands of sharks die every year because their fins are considered by some to be a delicacy.
But what about the Hammerhead’s bizarrely shaped head? And how does it help it to find its favourite food, the ray?
Hammerhead Sharks are found worldwide in tropical and temperate waters, where they are seen near shorelines and reefs as well as in open ocean far offshore. They have a lifespan in the wild of about 20-30 years and can grow up to 20 feet (6 meters) in length. That’s big! These monsters could weigh in at as much as 1,000 pounds (450 kg).
Their hammer heads, perhaps the most curious thing about them, enable their eyes to be set very much wider apart from most sharks. This gives them a much better visual range than other sharks. As well as providing a wider world view, the hammer shape to the head provides a wider base for their sensory organs. These highly specialised organs are spread out over a larger area on the head than your average shark and this gives them the ability to scan the ocean for food more thoroughly.
One group of the Hammerhead’s sensory organs is called the ampullae of Lorenzini, which allows sharks to detect, among other things, the electrical fields created by prey animals. The increased sensitivity in the Hammerhead’s ampullae allows it to find its favourite meal, the stingray, more easily. This is made all the more remarkable when you realise that the stingray usually buries itself in the sand!
The Hammerhead is far from a fussy eater though: they are known to eat fish, other sharks, squid, octopus, and crustaceans. Shockingly for us, they are also known to eat their own young, which are born viviparously. This means that the females give birth to live young. Fertilisation takes place internally with the male shark transferring sperm to the female through one of a couple of intromittent organs called claspers. The developing embryos are first sustained by a yolk sac which then transforms into something akin to a mammalian placenta through which the mother supplies sustenance until birth.
Read more about the Hammerhead Shark