Alien-like cookiecutter sharks terrorize animals of all sizes

The cookie cutter shark is known for eating large, cookie-shaped pieces of whales and sharks that are larger than them, but a new study has shown that they can terrorize all animals.
These green-eyed, alien-like sharks can grow to as long as 20 inches (50 cm) in length. Live Science reported that these strange creatures can use their pointed teeth for great white sharks up to 10 times their size. They are also known to eat chunks of human flesh.

Scientists often observed cookiecutter markings in larger animals, and assumed that this was what sharks primarily ate. A new study of shark specimens has revealed that these sharks eat animals at the bottom end of the food chain, giving them an unique role in the ocean ecosystem.

Aaron Carlisle (assistant professor at the School of Marine Science and Policy, University of Delaware) stated in a statement that "they feed on everything from white sharks and orcas to the largest, toughest predators like white sharks and orcas, all the way down to the smallest critters." "There are very few animals that can do this."

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According to the study, cookiecutter sharks (Isistius Brasiliensis), live in tropical and subtropical water and can reach depths of over 4,920 feet (1.500 meters). Cookiecutter sharks are often seen near the surface during the night when they hunt larger prey in higher oceans.

By studying 14 sharks taken from Hawaii by the Monterey Bay Aquarium, the researchers confirmed that these sharks prefer larger fish in the upper ocean. Although the sharks had very little food in their stomachs, the researchers were able to determine what they had eaten by examining the chemical composition of the tissues. The team also tested for environmental DNA (eDNA), which is the presence of DNA that has been left behind, even if there isn't any tissue available to study.

Carlisle stated that environmental DNA is a powerful and popular tool. It works on the principle that if an animal swims in the ocean, it will be shedding DNA in that water. You can take a water sample, filter it out and extract the DNA from all of the species that were in that water mass. We did that with their stomach contents.

Image 1 of 3 A preserved cookiecutter Shark on display at the Girls in Ocean Science Conference in California in 2016. (Image credit to MediaNews Group/Orange County Register via Getty Images/Contributor). Image 2 of 3. (Image credit to Pally/Alamy Stock Photo). Image 3 of 3. A side profile of the head of a cookiecutter Shark. Image credit: FLHC26/Alamy Stock Photo

Researchers discovered that cookiecutter sharks eat a lot of smaller species at lower depths. This includes crustaceans and small fish like members of the genuses Ariomma or Cololabis. These prey might be small enough to swallow whole by sharks. The study revealed that sharks ate less than 10% of large animals from the oceans.

These findings shed light onto the behaviour of this mysterious ocean creature. The study revealed that the shark sample was very small and came from a restricted geographic area. It is therefore unclear if this feeding trend is consistent across the global cookiecutter shark range.

The findings were published by the team in Scientific Reports on June 3.

Original publication on Live Science