By Douglas Main
Cookiecutter sharks aren't very neighborly. Like most sharks (or any marine animal, for that matter), cookiecutters roam the ocean looking for food. But unlike typical meat eaters, these sharks don't kill their prey — they just take a bite and move on.
And for the first time, scientists have found evidence that these small sharks even go after one of the world's most fearsome predators, the great white shark. Great whites are about 10 times the size of a cookiecutter shark.
Divers in a shark tank off of Guadalupe Island, which is about 150 miles (240 kilometers) west of Mexico's Baja California peninsula, took a photograph of a great white sporting a fresh bite from a cookiecutter, as documented in a study published recently in the journal Pacific Science. It's the first photographic evidence of such a bite, said study author Yannis Papastamatiou, a marine biologist at the Florida Museum of Natural History.
"Animals at the top of the food chain can still get attacked by things a lot smaller than them," Papastamatiou told OurAmazingPlanet.
Cookiecutter sharks leave a very distinctive scar when they bite; their specialized jaw allows them to "scoop out a hemispherical plug of flesh from their prey," according to the study. The sharks' name comes from the uniformity of the bite, which looks "like you took a cookie cutter to some dough," Papastamatiou said. "'Ice-cream-scoop shark' would be technically more accurate, but it doesn't have quite the same ring to it."
The sharks have been known to prey on a wide variety of marine animals, including swordfish, whales, orcas and even a human swimmer — and now, great white sharks. "This really shows there's no marine predator that can't be attacked by this little shark, which is impressive," he said. Scientists don't think bites from the cookiecutters can seriously harm these large predators.
The cookiecutter shark (Isistius brasiliensis) can grow up to 20 inches (50 centimeters) long, while great whites can reach lengths of nearly 20 feet (6 meters), according to the International Union for Conservation of Nature. Cookiecutter sharks range throughout the world in tropical and subtropical waters. They often dive during the day and come near the surface at night. One specimen was caught at a depth of 9,840 feet (3,000 meters), Papastamatiou said.
But how wise is it to attack large predator 10 times your size? There's almost no evidence of how often the cookiecutter's bold strategy fails, Papastamatiou said. However, researchers found one cookiecutter shark in the stomach of a large bluefin tuna, suggesting the tactic isn't foolproof.