A Tiny Shark Bit a Perfect Circle Into a Great White's Head and Scientists Are Thrilled

The Ocean's Most Surprising Bully

It sounds like something out of a science fiction film: a 16-foot apex predator, one of the most feared animals on Earth, swimming around with a perfectly circular hole punched into the top of its head. But this is no mystery — and the culprit is far smaller than you'd expect. The California White Shark Project shared a video of a 16-foot female great white shark with an unusual scar on the top of her head. As she swims toward the camera, a perfect circle becomes visible — almost like a dolphin's blowhole — revealing the telltale plug of missing flesh left by a cookiecutter shark.

The cookiecutter shark is a specialized predator that uses a fused bottom row of teeth to scoop out a circle-shaped chunk of flesh. Unlike typical meat eaters, cookiecutters don't kill their prey — they just take a bite and move on. And apparently, no target is too intimidating. Great whites are about ten times the size of a cookiecutter shark. None of that seems to matter to the cookiecutter.

Scars as a Scientific Road Map

By reviewing more than 2,500 video clips of over 500 individual white sharks filmed between 1987 and 2022 in central California, a team of scientists led by Dr. Scot D. Anderson of the California White Shark Project developed a classification system for different types of wounds. The resulting study was published in the journal Frontiers in Marine Science in 2025.

Each scar was placed into one of five major categories based on its shape, depth, location, and other visual cues: injuries from other sharks, prey interactions, environmental contact, parasites, or human-related damage. "The scars and wounds seen on the sharks tell us about their interactions with each other, their environment, their prey and humans," explained Scot Anderson, Senior Researcher at the California White Shark Project and co-author of the study. Think of it as a biography written directly onto the animal's skin.

Wounds from boat propellers are characterized by evenly spaced parallel cuts along the body, while wounds from large squid are characterized by rows of circular scars which taper in diameter, consistent with large tentacles. Other types of scars might indicate boat strikes, defense wounds, or scrapes from rocks — and some can even reveal if the sharks have been mating. Females might carry "light impressions" from bites on their heads and pectoral fins from a mating encounter.

What a Cookie-Cutter Bite Reveals About Migration

The circular wound on this great white isn't just a curiosity — it's a geographic clue. "Cookiecutter wounds can tell us the white sharks get these marks during the 'offshore phase' of their migration, as that is when they overlap habitat with cookiecutter sharks," said Anderson. In other words, that strange hole on the shark's head is essentially a stamp in her passport, proof of where she's been.

White shark mating remains a mystery, but if researchers see fresh hold bites and cookiecutter marks healing at similar rates on the same individuals, it suggests both occurred around the same time and place — likely during the sharks' open ocean migrations. Future studies can capitalize on both the rate of healing and the new categorization scheme to identify when, where, and how various scars occurred, informing further understanding of their life history.

Reading the Scars to Protect the Species

The California White Shark Project conducts research on white sharks off the California coast to enable scientific discovery, inform policy, and conservation measures. The new scar classification system gives that mission a powerful new tool. Every wound catalogued is another data point that can help distinguish natural predation from human-caused harm — a distinction that matters enormously for conservation.

Understanding the scars on great white sharks can help with conservation efforts. By identifying threats such as boat strikes and fishing gear entanglement, conservationists can implement strategies to protect these vulnerable creatures. The ocean keeps most of its secrets. But written across the bodies of its greatest predators, in circles and crescents and parallel lines, is a record of everything they've survived — and scientists are finally learning how to read it.