Sharks Use Manta Rays as Back Scratchers

Galapagos sharks have an itch problem. They've also figured out a solution: use a manta ray as a living, very reluctant loofah.

Researchers documented it at three sites near Mexico's Revillagigedo archipelago over fourteen months, from late 2024 into early 2026, watching sharks press and drag themselves along both surfaces of manta rays. They weren't random about it. Snout and gill areas are prime sea lice territory, and the sharks went directly for those spots, which is how researchers ruled out aggression and landed on "using this ray as a loofah."

The mantas were not fully on board. Juvenile sharks got mild tolerance, a shuffle and not much more. Adult sharks triggered full flight mode: the mantas rolled backward and tried to escape what looked like a potential bite.

All of this happened at or near established cleaning stations, suggesting sharks may opportunistically use mantas as alternative cleaning substrates. Researchers note the behavior may signal real behavioral plasticity in sharks, though it raises concern about costs to the mantas, particularly if ectoparasites or pathogens transfer in the process.

How sharks discovered the trick remains unclear. One researcher wonders whether smaller fish scratching themselves on sharks gave them the idea. Another suspects an individual simply tried it, found it worked and kept going.

The ocean has an entire economy of animals scratching each other. Sharks just cut out the middlefish.

Read the full story at Scientific American, June 16, 2026

Hot Take: Every apex predator secretly has a weird little need it can't handle alone, and there is something deeply comforting about that. The most alarming thing in this story is that the ocean has sea lice.