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What Bit This Great White Shark? A Cookie-Cutter

Great white shark with suspected cookie-cutter shark scars. Credit: G. del Villar/Pacific Science.

Every year, between August and December, great white sharks arrive at the western coast of Mexico, and people jump into the ocean to see them. Operators chum the waters to lure in the sharks, while divers enter in floating steel cages.

On 25 August 2010, one of these divers, Gerardo del Villar, saw a great white shark off Guadalupe Island with two odd wounds on its head. One was a crescent-shaped scar. The other was a round crater, still open and bloody. Both were just behind the corner of the young male’s fearsome mouth. Del Villar took photos of the animal and sent them to a team of scientists, including Yannis Papastamatiou from the Florida Museum of Natural History.

He had seen wounds like these before. “A wound from a hook should leave more of a hole and would not be as smooth,” he says.  Instead, Papastamatiou thinks that they were the bite-marks of another shark, just a sixth of the size—a cookie-cutter. “I dont know of any other animal that leaves a bite like that.”

Cookie-cutter shark, by the NOAA Observer Project

There are three species of cookie-cutter sharks, but only one that’s known to swim off Mexico – Isistius brasiliensis. It looks like a demonic cigar. It’s a small cat-sized animal with chocolate-coloured skin, a rounded snout, and large green eyes. Beneath the bizarre head, its lower jaw contains what looks like a saw—a row of huge, serrated teeth, all connected at their bases.

Cookie-cutter shark lower teeth, byKarsten Hartel, NOAA

When the cookie-cutter finds a victim, it latches on with its large fleshy lips and bites down with its saw blade. With twisting motions, it scoops out a chunk of flesh, leaving behind circular craters exactly like those that del Villar saw on the great white. These are serious injuries—the biggest craters ever recorded were 5 centimetres wide and 7 centimetres deep. (These chunks are conical, so the cookie-cutter metaphor isn’t quite right; “Ice cream scoop shark” or “watermelon baller shark” are more accurate, if less catchy.)

Shark want cookie

Papastamatiou cautions that we can’t be sure of what happened, but here are some plausible guesses. Cookie-cutters spend the daytime at depths of up to 3,500 metres, where no great whites venture. But they rise to the surface at night, and one of them may have encountered our poor shark during such an excursion.

Cookie-cutters glow. Their entire undersides give off a vivid, green light, except for a dark collar around their throats. Some scientists have suggested that they use this light to turn themselves into bait. The glow matches moonlight and starlight beaming down from above, rendering the sharks invisible to any predators looking up from below. That is, except for the dark collar, which resembles the silhouette of a fish. The predator comes in for a closer look, and the cookie-cutter attacks.

This is all speculation – no one has ever seen a cookie-cutter attack. We only have the scars to go on. But the luring hypothesis could explain why the great white was bitten near its mouth, rather than some less dangerous body part like a tail or underside. Maybe it tried to make a meal of the cookie-cutter and became a meal instead.

If this actually happened, it was probably a rare event. Divers off Guadalupe Island have amassed the largest catalogue of white shark photos, and many individuals have been seen year after year. None of these other individuals had similar wounds. The fact that the youngster had two might mean that the cookie-cutter launched an unsuccessful strike, leaving the crescent-shaped wound, before finally getting a proper mouthful.

Cookie-cutters vs. everything

French naturalists discovered the cookie-cutter in the early 19th century, but no one connected this bizarre creature to the weird craters found on large fish until the 1970s. For years, these wounds were a mystery. People wondered if they were caused by other predators, parasitic lice, lampreys with their round toothy suckers, or even bacterial infections.

The first breakthrough came in 1963, when a man called Donald Strasburg noticed that the cookie-cutter shark would shed its saw-like lower teeth as a single unit. By contrast, other sharks replace their teeth one at a time. In 1971, Everet Jones discovered small conical plugs of flesh in the stomachs of these sharks. He also noticed that their mobile tongues and large lips allow them to form a vacuum on a smooth surface. It became clear that this tiny animal was wounding some of the ocean’s mightiest residents.

Cookie-cutter shark bites on a Gray's beaked whale, by Avenue

The cookie-cutter has a distinguished track record of turning the tables on top predators. Its list of victims includes: killer whales; at least 48 other species of whale or dolphin; many types of shark; fur, leopard and elephant seals; dugongs; stingrays; and big bony fish like tuna and swordfish. (It’s a risky strategy that occasionally fails–one whole cookie-cutter was found in the stomach of a large tuna.)

Humans are fair game too. In 2004, a Japanese team found the shark’s distinctive circular scars have been found on the corpse of a 60-year-old woman who had likely drowned herself beforehand.  And in 2009, a cookie-cutter bit a man who was attempting the 30-mile swim between Hawaii and Maui at night. The shark carved a chunk out of his chest and calf. (Update: Al Dove interviewed the poor guy!)

The fearless cookie-cutters have even disabled the most dangerous ocean creature of all—the nuclear submarine. They attacked exposed soft areas including electrical cables and rubber sonar domes. In several cases, the attacks effectively blinded the subs, forcing them back to base for repairs. They later returned, fitted with fibreglass coverings.

Yet more bonus material: Here’s a recent video showing a dolphin with a nasty cookie-cutter injury. Hat-tip to Justin Gregg

Bonus: Here, from shark scientist David Shiffman, is some sage advice on how to avoid being bitten by a cookie-cutter shark:

Reference: Hoyos-Padilla, Papastamatiou, O’Sullivan & Lowe. 2013. Observation of an Attack by a Cookiecutter Shark (Isistius brasiliensis) on a White Shark (Carcharodon carcharias). Pacific Science http://dx.doi.org/10.2984/67.1.10

Hat-tip to Douglas Main for alerting me to this story.



24 thoughts on “What Bit This Great White Shark? A Cookie-Cutter

  1. I believe it was a squid or octopus because of the crater it left. The wound is to new to be a cookie cutter shark and besides the scar on the right of it is heald. So if it was a tentacle that was stuck on the side of the shark after it was ripped from the squids body that might be a possible different idea.

  2. @TsHojack – Squid and octopus suckers don’t do that. They don’t rip flesh. Some sperm whales have circular scars due to the tentacles of large squid, but those are thin rings, not huge gaping craters.

    The comment about it being too new doesn’t make sense – lots of cookie-cutter injuries look like that, including the dolphin in the video.

  3. Left scar is very similar to the scar made by the cookie-cutter shark. Right scar is probably by the cookie-cutter. We made close dissection of the cookie-cutter shark and discussed how they make such strange scars. If you are interested, see Shirai, S. and K. Nakaya (1992): Functional morphology of feeding apparatus of the cookie-cutter shark, Isistius brasiliensis. IN: Zoological Science, 9: 811-821. If you want, I can send you PDF of the paper.

  4. I am shocked at this “cookie cutter” shark. I have never heard of one before. Great. Another thing to be fearful of in the ocean!

  5. Sorry, Ed Young, but squid, specially the giant, have suckers with some nasty fang-like hooks that leave a wicked wounds.

  6. It was a Cookie-cutter shark. Those little critters have been known to latch themselves to and take bites out of submarines.

  7. Wow I never heard of a cookie-cutter shark before neither the fact that they leave such dangerous wounds. This is something new to me.

  8. As much as we know about the oceans only shows that there is much more to learn. And mere shifting of 1% of funds from the armament programs could be an enormous boost to the marine science – not to mention the boost in the resulting values. So why it is so difficult to see sense?

  9. I found some other pictures of the CCS online, including some “babies”, which made me think of the “Dobie-o-Matic”, contrived by Gary Larson for “The Far Side”.

    A “Cookie-Cutter Shark-o-Matic” launcher/gun was the inevitable result.

  10. “Don’t swim at night, over a deep sea trench, while being lit from above by boat-based floodlights.” …well that’s my favorite time to swim…what am I going to do now?

  11. I first learned about C-C from watching a cartoon show, Octonauts, with my 3-yr grandson that loves the show and one episode was “Cookie Cutter Sharks”. It was one of his favorites and on a recent visit we watched it over-and-over-and-over. It was interesting to hear and read about them from another source. An interesting aspect was that the episode dealt with the C-C damaging the underwater vehicle of the Octonauts, similar to the account on C-C damaging submarines.

  12. Based on what i’ve seen and heard from these i do think it was a CC. Not very animals would take on a great whit and those who would don’t leave holes like that. The CC might be small enough to slip past the great white without it noticing and take a bite off of it’s side. Also i agree with Seph, who the f#$@ swims 30 miles in the dark across the PACIFIC OCEAN!

  13. It was not the cookie cutter it was the infamous C. Megladon. They are still up to 100ft in length but they have evolved tiny mouths that have teeth protruding straight forward and individual muscles flex to make them close in the cone like shape.

    But wow that CC bite on that dolphin looked pretty nasty. I imagine that was quite painful. I bet that guy swimming the dark enjoyed his encounter with the new C. Megladon also.

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