Cookie cutter sharks (Isistius brasiliensis) may be small (reaching under two feet in length), but they pack a hefty bite, as a swimmer found out to his cost.
Cookie cutter sharks are so named because of their feeding habit of gouging out round plugs of flesh from larger animals, somewhat in the manner of a cookie cutter.
The sharks, known from tropical and warm temperate oceans worldwide, typically feed by biting chunks out of larger marine mammals and fishes, as well as consuming entire squid.
Their love of biting chunks out of larger entities is not restricted to living organisms; the fearless sharks also display a penchant for taking bites out of US Navy submarines, oceanographic equipment and telecommunication cables.
Although reports of attacks on humans have been reported, they have remained unsubstantiated until Randy Honebrink and colleagues documented one in a paper to be published in a forthcoming issue of the journal Pacific Science.
Swimmer Mike Spalding was attempting to swim the Alenuihaha Channel between the Hawaiian islands of Hawaii and Maui in March 2009, when he was bitten in the lower chest and left calf by one or more Cookie cutter sharks.
The incident occurred soon after the vessels (a powered boat and a kayak) escorting Spalding turned on their lights. The lights attracted squid, which in turn probably attracted Cookie cutter sharks to the scene, resulting in the bites.
Spalding was taken to a hospital, where his wounds, one of which measured about 10cm/4" inches in diameter, had to be treated with skin grafts.
Although the bites can be fearsome, Cookie cutter sharks feed near the surface only at night, so daytime swimmers have little to fear.
The authors of the study advocate taking special care when swimming at night in tropical seas near lights, during periods of bright moonlight, or in the presence of bioluminescent organisms.
For more information, see the paper: Honebrink, R, R Buch, P Galpin and GH Burgess (2011) First documented attack on a live human by a cookiecutter shark (Squaliformes, Dalatiidae: Isistius sp.). Pacific Science.
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