On continental shelves the world over, the great hammerhead shark (Sphyrna mokarran) cruises through shallow tropical waters in search of prey. Its widely set eyes, which provide the shark with exceptional binocular vision, aren’t the only tool the predator deploys in its quest. Like a beachcomber armed with a metal detector, the solitary hunter sweeps its hammer-shaped head, called a cephalofoil, over the sand, scanning for the electrical signals emitted by its preferred quarry: stingrays.
Once detected, a stingray, no matter how well-hidden, stands little chance of escape. The shark uses its well-adapted head to pummel and pin the stingray down while dispatching it with a series of swift bites. Although a stingray may put up a fight with its toxic tail barb, hammerheads are thought to be immune to the venom the barb delivers.
In this ecosystem, the great hammerhead shark appears to be a perfectly adapted apex predator. But there’s one species that poses threats for which it has few defenses. Humans have taken a heavy toll on this and many other shark species, snagging them on longlines, hauling them up in nets as bycatch, and ruthlessly targeting them for their fins (which, despite international pressures against their trade, are still a hot commodity in Asian markets). Over the past 25 years, great hammerhead populations have declined by at least 80 percent—so much so that the International Union for Conservation of Nature (IUCN) lists the species as Endangered worldwide.
In order to protect the sharks and their habitats, scientists are racing to better understand where and how they live. Although the animals gather in large seasonal spawning aggregations, they are generally solitary and wide-ranging, so their whereabouts are tough to pin down. However, one team of researchers has developed a method for identifying individual hammerhead sharks via laser wherever they are encountered. Without having to capture the animals, the researchers can identify the sharks and track their movements and growth patterns from year to year.
Based on results from studies like these, along with regulations that protect the animals from exploitation, many feel hopeful that there is light at the end of the sharks’ tunnel. Despite recent population declines, experts now say the great hammerhead is at a low risk for extinction within the next 50 years. And the more scientists can learn about these extraordinary animals’ life history and critical habitats, the better chance they have of saving them.
Christine Shepard is a professional photographer, cinematographer, and entrepreneur based in Kona, Hawaii. She’s been named a finalist in BBC’s Wildlife Photographer of the Year and a Highly Honored Winner in Nature’s Best Photography Competition. Christine’s work has been widely published in magazines including National Geographic, Popular Science, and Scientific American, and her personal spotlight stories have been featured on the Discovery Channel and Oprah’s O Magazine.