These are incredible animals. My parents have a beach house and since I was young, I was used to go with my father early in the morning to watch fishing boats unloading their catch and to buy fresh fish, including sharks. I was always amazed with the hammerheads: they seemed even scarier than other sharks. They were part of my early dream to become a SCUBA diver and later specialize in marine wildlife.
Back to their head: These sharks' broad, flat, hammer-shaped heads are called cephalofoils, and no other creature in the world has a head quite like it. Hammerheads, like all other sharks, have sensory organs that can detect the electric fields of prey in the water; some scientists hypothesize that the broad cephalofoils allow hammerheads to have more of these organs—therefore allowing them to better sense prey. A 2002 experiment seemingly lent credence to this notion. Although the researchers didn’t find a difference in sensitivity to the electric fields between a hammerhead and a cone-nosed sandbar shark, the hammerhead was able to search a larger area, which the researchers say would “increase the probability of prey-encounter.” The researchers also noted that the hammerhead was more maneuverable than the sandbar shark.
Why are they so maneuverable? They use it to hunt at the sea floor in sand beds, looking for marine life hidden from predators’ eyes, but not from the hammer's superior senses. Let’s see that in practice with a stingray, for example. Pay attention on their circular movements around the potential prey.
Their superb sense and head shape have also to do with their separate eyes. Why are they so separate? Their wide-set eyes give them a better visual range than most other sharks. And by spreading their highly specialized sensory organs over their wide, mallet-shaped head, they can more thoroughly scan the ocean for food.
While being monitored, the sharks spent 90 percent of their swimming time tilted to one side, usually at an angle of 50 to 75 degrees. Why’d they do this? It’s thought that after a hammerhead rolls sideways, the creature’s first dorsal fin acts like one of the pectoral fins. This reduces drag while also increasing the animal’s “wingspan.” Both factors enable the shark to swim more efficiently.
And with their eyes far on the side, it is a perfect combination!
In 2009, biologist Michelle McComb and her team captured live bonnetheads, winghead sharks, and scalloped hammerheads to test their vision. They attached recording devices right below the sharks’ corneas and monitored the fishes' eye movements while sweeping light beams across their faces. The researchers found that the binocular overlap in the hammerheads' field of vision is up to three times higher than it is in lemon and blacknose sharks—both of which have cone-shaped snouts. That means hammerheads have superior depth perception when compared to other sharks.
Back to their complex head shape: One group of sensory organs is the ampullae of Lorenzini, which allows sharks to detect, among other things, the electrical fields created by prey animals. The hammerhead's increased ampullae sensitivity allows it to find its favorite meal, stingrays, which usually bury themselves under the sand.
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