Monster Monday—A Real-Life Cookie Monster
January 11, 2016
While sharks are among the most feared of all sea creatures, you might think a small fish called the cookie-cutter shark sounds harmless enough—until you see its teeth! These fearless sharks attack much larger prey with a fiendish “hit-and-run” technique. The cookie-cutter shark, which has the scientific name of Isistius plutodus, locks onto its prey with its pointy upper teeth and spins its body so the lower teeth carve out a perfectly circular plug of flesh. The victim is left with a shallow cookie-shaped hole in the side of its body, wondering what just happened, while the shark beats a hasty retreat.
For years, scientists who examined the odd teeth of the cookie-cutter were not certain how the predatory fish fed. The tiny shark, only about 2 feet (60 centimeters) in length, has an upper jaw full of 30 to 40 straight, needlelike teeth. The teeth in the lower jaw are much larger, with a broad, triangular shape. Relative to its body size, the cookie-cutter has the largest teeth of all sharks. Rarely had scientists seen such a mismatched pair of jaw and teeth in a single animal. Eventually, scientists realized the small sharks were behind the mysterious reports by fishermen of odd, perfectly circular wounds occasionally found on such large fish as marlin and tuna, as well as on some seals and whales. The cookie-cutter’s lower teeth are all connected to each other at the base to form a continuous sawlike edge that is perfect for carving chunks of flesh off prey.
Scientists believe the cookie-cutter shark may lure victims into close range by using light-producing organs, called photophores, located on the lower part of the body. When the prey approaches to investigate the strange lights, perhaps in search of its own meal, the shark attacks. Some scientists, however, think that cookie-cutter sharks use this bioluminescence for protection. Seen from below, the glowing shark blends in with the moonlight above, becoming almost invisible.
As frightening as the cookie-cutter shark seems, it does not pose much threat to humans. Throughout the world, the sharks dwell in the deep oceans, below 3,300 feet (1,000 meters), during the day. They only come closer to the surface at night to feed. Because humans rarely swim in the oceans at night, there is not much possibility of encountering the cookie-cutter. There are, however, a few reports of nighttime swimmers who have been attacked by cookie-cutter sharks, with the circular wounds to prove it. These aggressive sharks are known to strike at any large prey in search of a quick meal. There are even reports of this shark leaving its distinctive bite marks on the hull covering of a U.S. Navy submarine!