Cookiecutter Shark

The cookiecutter shark uses its specialized suction-cup lips and heavily serrated lower teeth to carve out perfectly circular plugs of flesh from large marine animals like whales, dolphins, and sharks. It latches onto its prey, spins its body to cut through the tissue, and then swallows the chunk of meat. This parasitic feeding strategy leaves distinctive crater-like wounds on its victims.

The shark's ventral surface is covered in photophores that emit a pale blue glow, matching the downwelling light from the surface and making it invisible to predators looking up from below. However, it has a dark, un-illuminated collar around its neck that acts as a lure. Larger predatory fish mistake this dark patch for a small prey item, swimming close enough for the cookiecutter shark to take a bite out of them.

Cookiecutter sharks are deep-sea dwellers known for a behavior called diel vertical migration, meaning they spend the daylight hours at extreme depths, often down to 3,500 meters (over 11,000 feet). At night, they migrate up to shallower waters, usually around 85 to 300 meters deep, to feed. This brings them into contact with the larger marine mammals and fish they prey upon.

Attacks on humans are incredibly rare, but there are a few documented instances of cookiecutter sharks biting long-distance swimmers in deep ocean waters. These bites usually occur at night and result in deep, circular crater wounds that can be difficult to treat. However, because the shark is relatively small, usually under 50 centimeters long, it is not considered a lethal threat.