Cookiecutter Shark

The Cookiecutter Shark is a small but highly specialized deep-sea shark in family Dalatiidae, notable for its unusual parasitic feeding strategy of gouging round plugs of flesh from much larger marine animals including whales, dolphins, large fish, and other sharks. Despite its small adult size of roughly 40-56 centimeters, it uses a combination of bioluminescence and powerful jaws to lure and bite prey far larger than itself. It inhabits deep tropical and subtropical waters worldwide. The species is currently assessed as Least Concern given its wide distribution and lack of direct commercial fishing interest.

• Small, cigar-shaped, cylindrical body, uniformly dark brown to gray with a soft, gelatinous feel
• Distinctive dark collar-like band encircling the throat region, contrasting with a bioluminescent pale underside
• Large, round eyes adapted for low light
• Small, underslung mouth with large, triangular, interlocking lower teeth used to gouge circular wounds
• Short, rounded dorsal and pectoral fins set far back on the body Its small cigar-shaped body, dark throat collar, and characteristic round parasitic bite wounds left on much larger prey make it unmistakable, despite rarely being seen alive.

Cookiecutter Sharks are found in deep tropical and subtropical waters worldwide, generally in open ocean far from shore, undertaking a daily vertical migration from depths of up to 3,700 meters during the day to near-surface waters at night. This migration follows the deep scattering layer of prey and allows access to larger prey species that come close to the surface after dark. Their range spans all major ocean basins between roughly 20 to 30 degrees latitude on either side of the equator, and they are rarely encountered by humans given their deep daytime habitat.

Cookiecutter Sharks employ a distinctive parasitic feeding strategy, using a glowing bioluminescent underside to lure predators or attract passing large animals, then attaching to the skin with suction from their lips and rotating to excise a round, cookie-shaped plug of flesh using their specialized lower teeth. Prey targeted includes whales, dolphins, large sharks, tunas, and even submarine equipment and cables. They migrate vertically each day, rising toward the surface at night to feed and hunt in darker deep water during daylight. Reproduction is presumed ovoviviparous, though details remain poorly documented.