The name "cookiecutter shark" refers
to its feeding habit of gouging round plugs, like a cookie cutter, out of larger animals. Marks made by cookiecutter sharks have been found on a wide variety of marine mammals and fishes, as well as on submarines, undersea cables, and even human bodies. A school of these fierce, 12 in long fish with blunt snouts once attacked an underwater photographer on an open ocean dive. It also consumes whole smaller prey such as squid.
Cookiecutter sharks can hover in the water column and likely rely on stealth to capture more active prey. They are bioluminescent underneath, except for a dark collar near the chin, The predator, swimming below the cookiecutter, only sees the small collar. Thinking it has found dinner it speeds in for the kill. But when it gets to the would-be snack....twist and scoop! The tables have been turned and the ex-predator becomes the cookiecutter’s prey. Now that’s sneaky.
The shark first secures itself to its prey by using its flabby suction lips ensure a tight seal. It then bites, using its narrow upper teeth as anchors while its lower teeth slices into the prey. It's lower teeth are bigger compared to it's body size than any other shark. Finally, the shark twists and rotates its body to complete a circular cut, aided by the initial forward momentum and subsequent struggles of its prey. The bites don't kill their hosts, they live to return for countless visits .
The action of the lower teeth may also be assisted by back-and-forth vibrations of the jaw, a mechanism akin to that of an electric carving knife. This shark's ability to create strong suction into its mouth is likely also of utility in capturing smaller prey such as squid.
The prevalence of these attacks can be high; off Hawaii, nearly every adult spinner dolphin bears scars from this species.
The cookiecutter shark regularly replaces its teeth like other sharks, but sheds its lower teeth in entire rows rather than one at a time. The old sets of teeth are swallowed, so that the shark can recycle the calcium content.
The intrinsic green luminescence of the cookiecutter shark is the strongest known of any shark, and has been reported to persist for three hours after it has been taken out of water.
One of the earliest accounts of the wounds left by the cookiecutter shark on various animals is in ancient Samoan legend, which held that atu (skipjack tuna) entering Palauli Bay would leave behind pieces of their flesh as a sacrifice to Tautunu, the community chief.