Isistius brasiliensis, known as the cookie cutter shark or cigar shark, is a small species of shark living in warm oceans around the world. These sharks only grow between 42-56cm (16.5-22in). They are famous for taking ferocious bites out of much larger animals, leaving round scars in the prey’s flesh. Despite their small size, these sharks are skilled predators (or parasites), specially adapted for hunting and vertical migration.
1. Cookie cutter sharks feed by latching onto larger animals and biting out a chunk of flesh
Cookie cutter sharks are small fish that prey on much larger ones. Cookie cutter sharks feed on sharks, dolphins, and even whales. But they don’t kill their prey. Instead, these sharks latch onto larger fish with their lips (which are like suction cups) and then bite a chunk out of the animal with their razor sharp teeth. Cookie cutter sharks earned their nickname because the bites they take out of prey look like cookies cut from dough. Before that, shark expert Stewart Springer called them “demon whale biters.” But this is not as adorable as cookie cutter.
The shark also feeds on smaller squids, fish, and crustaceans
The cookie cutter shark isn’t considered a typical parasite because it doesn’t just feed on larger hosts. Instead they are called facultative ectoparasites. Cookie cutter sharks also eat small squids, fish, and crustaceans. Although they are more famous for chewing chunks of flesh, they don’t depend on feeding off large animals like true parasites to survive.
2. The average cookie cutter shark bite is 2cm wide and 7cm deep
Cookie cutter sharks don’t kill their prey, but their bite definitely hurts! The average cookie cutter shark bite is 2cm wide and 7cm deep. On larger animals, the shark bites deep into the skin’s tissue, but doesn’t reach muscle or bone. Many dolphins swimming near Hawaii are covered in these bites. Large animals can survive multiple bites. But smaller ones, such as tuna, are more likely to die from the deep wound.
Cookie cutter sharks rarely attack humans
Cookie cutter sharks live in warm waters around islands like Hawaii. Even though people are always swimming or surfing where cookie cutters hunt, there have only been a few documented attacks on humans. The men were swimming in the waters between islands (called channels) when cookie cutter sharks bit them. However, none of the attacks were fatal, and the men were able to swim after being treated.
3. The cookie cutter shark has 30-37 teeth in the upper jaw and 21-31 teeth in the lower jaw
Cookie cutter sharks have between 51-68 teeth total. Their upper jaws have between 30-37 teeth. While their lower jaws have between 21-31 teeth. The teeth in the upper jaw are small and straight. These teeth are like hooks because the shark uses them to hold onto prey. The bottom teeth are large, triangular, and very sharp. While the top teeth keep a hold of prey, the bottom teeth are for taking a vicious bite.
All of the teeth on each half of the jaw are fused together
Unlike other sharks, cookie cutters don’t have individual teeth. Instead, the teeth in each part of the jaw are fused together. If you look at a cookie cutter shark’s jaw, you might think it only has one long tooth on each half of the jaw! But even though the teeth are fused at the base, they are still considered individuals.
4. The cookiecutter shark sheds entire rows of teeth at once
Since the teeth are all fused together, cookie cutter sharks don’t lose one tooth at a time. Instead, they regularly shed entire rows of teeth at a time. By the time a cookiecutter shark is 50cm (20in), it will have shed 15 sets of lower teeth. That’s between 435-465 teeth.
The shark swallows its bottom row of teeth, possibly for the calcium
When the cookie cutter shark sheds its teeth, it swallows the bottom row. Cookie cutters have very dense skeletons. And their strong jaws and skulls make their bites so powerful. So many scientists believe that cookie cutters swallow their teeth to absorb the calcium.
5. The underside of a cookie cutter shark is covered in small dots of light hide it from prey
Almost the entire underside of a cookie cutter shark is covered in tiny dots called photophores, that emit a greenish light. However, the light doesn’t help the shark stand out, it helps it blend in. Like camouflage, the light makes the shark blend in with its surroundings. This is called counter-illumination, and it helps protect the shark from predators and sneak up on prey. Cookie cutter sharks often swim in schools to increase this bioluminescent effect.
Cookie cutter sharks glow for three hours after being taken out of water
The shark doesn’t control its photophores. Instead, counter-illumination occurs naturally. Because of this, cookie cutters glow for three hours after they are killed or removed from the water. This phenomenon fascinated early zoologists so much that the shark’s genus name, Isistius, honors the ancient Egyptian goddess of light, Isis.
6. Cookie cutter sharks have dark “collars” around their throat to attack predators
Cookie cutter sharks have a dark patch of skin near their gills, around the top of their underside. It looks like a collar around what you can think of the shark’s throat. When cookiecutter sharks swim closer to the surface at night, their collars look like small fish. This attracts larger predators, such as dolphins, whales, and other sharks. When the large predator gets closer, it’s in for a nasty surprise. That fish is actually part of a cookie cutter shark, who turns the would-be predator into prey!
7. Cookie cutter sharks live 1000m below the ocean surface, but migrate upwards every night to hunt
Cookie cutters are deep water sharks. The sharks usually live 1000m (3280ft) below the ocean surface. Some have been found living as deep as 3500m (11482ft) below the surface. Every night, they migrate hundreds of meters closer to the ocean surface in order to hunt. Their unique collars and bioluminescence lure prey upwards. Because of the migration, cookie cutter sharks are better adapted to swimming vertically than horizontally.
8. Cookie cutter sharks have holes behind their eyes that keep them stable during migration
Cookie cutter sharks, like other sharks, have spiracles behind their eyes. Spiracles are holes that intake water that is expelled through the gills. Shark spiracles have a fake gill called a pseudobranch. Many experts believe that the pseudobranch also helps the shark regulate pressure. These sharks quickly migrate between different water pressures, so it is possible that the spiracle keeps the shark’s pressure stable.
9. These sharks are super agile thanks to one broad, symmetrical caudal fin
Cookie cutter sharks have caudal fins that are broad, symmetrical, and shaped like paddles. These caudal fins are why the shark is so agile. Even though they are not the best swimmers, cookie cutters can maneuver quickly around prey to take a bite. However, they do not have anal fins. Anal fins provide stability for sharks. So not having one could be why cookie cutter sharks aren’t as good swimmers.
10. Cookie cutter shark pups are born ready to hunt
Female cookie cutter sharks have two working uteri. Unlike humans, who only have one uterus. Male cookie cutters fertilize the eggs inside the female. The female then carries the eggs until they hatch inside her. It usually takes between 12-22 months for the eggs to hatch. After hatching, she gives birth to 6-12 pups, who are fully developed and ready to start hunting.
Don’t worry about cookie cutter sharks biting, unless you’re in an old submarine!
In the 1970s and 80s, mysterious attacks on the rubber domes and electrical cables of US Navy nuclear submarines were leaving the submarines blind and needing constant repairs. Although the Navy feared enemy attack, the culprit turned out to be hungry cookie cutter sharks! The Navy covered the rubber with fiberglass to prevent the sharks from eating it. While officers were annoyed, you can’t deny that it takes guts to eat a nuclear submarine!
How endangered is this animal?
The International Union for Conservation of Nature considers cookie cutter sharks of least concern. This means that the population is not threatened, and conservation efforts aren’t necessary. The shark is not fished commercially. It is very small and no one really wants to eat it. A few sharks are occasionally caught accidentally while companies are fishing for more valuable creatures. However, this is rare and not a serious threat to the species.
Cookiecutter shark - Wikipedia
Cookiecutter shark - Isistius brasiliensis — Shark Research Institute (sharks.org)
Smalltooth Cookiecutter Shark - The Australian Museum
ADW: Isistius brasiliensis: INFORMATION (animaldiversity.org)
Cookiecutter Shark (oceana.org)
This Tiny Shark Can Take Out Nuclear Submarines (businessinsider.com)
Cookiecutter Sharks ~ MarineBio Conservation Society
Also Known As
Cigar shark, Luminous shark
42–56 cm (16.5–22 in) in length
Atlantic, Southern Indian and Pacific Oceans
Open ocean (epipelagic to mesopelagic)
Squids, mesopelagic teleost fishes, crustaceans, sharks, and cetaceans
Lifespan of cookiecutter shark is unknown