If Rudyard Kipling was writing a `Just So' story for the hammerhead shark,he'd surely have come up with a tale of a three way struggle that produced the fish's distinctive profile. Although Kipling's story would be highly entertaining, Stephen Kajiura has got a much more realistic theory. All sharks are endowed with an electrical sense, that allows them to sense the weak electrical fields that most creatures emit. Kajiura wondered if the hammerhead's odd shape gave it a head start over other electrosensing sharks. Tempting hammerheads and more classically shaped sharks with decoy dipoles,Kajiura has discovered that the shark's extended head allows it to search for food over much larger areas than its more streamlined relatives(p. 3609).
There are a variety of possible explanations for how the fish's distorted features evolved, ranging from wide angle binocular vision and stereo smell to electroreception. Sharks are one of the few...
