Animal of the Week: The cookiecutter shark (Isistius brasiliensis) is somewhat less friendly than its name may make it sound, and also significantly smaller.
Also known by the only-slightly-scarier name of “cigar shark”, the cookiecutter shark tends to be around 42–56 cm when fully-grown, and likes to live near islands.
It gets its name from its annoying habit of using its mouth to gouge holes in the sides of larger animals, like a cookie cutter. Of course, it sometimes gets it wrong, and has been known to leave marks on submarines, as well as people.
Luckily, it’s rarely encountered by humans, since it likes to stay pretty deep in the ocean, and there have only been a handful of attacks on humans by cookiecutter sharks—so they’re one less thing to worry about next time you go to the beach.
It moves up towards the surface at night, and descends back into the depths of the ocean in the daytime, so you might want to be slightly more careful if you fancy a midnight swim, but only if it’s a very deep midnight swim.
Compared to its shark cousins, this parasite isn’t particularly menacing—presumably the reason it doesn’t bother to attend family reunions any more—but it can leave some unsightly holes in its victims, averaging 5 cm across and 7 cm deep. I expect the victims need that like they need a hole in the head…