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Planet Earth

The Hagfish's Special Trick for Warding Off Predators: Thick, Sticky Mucus

A shark can't eat you if it's gagging on slime.


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Sharks are superb predators, but even they are no match for the animal kingdom’s most disgusting yet effective defense: the gag-inducing slime of the hagfish.

Hagfish are elusive deep-sea creatures that have mucus-secreting glands positioned all over their long, writhing bodies. Last fall marine ecologist Vincent Zintzen of the Museum of New Zealand Te Papa Tongarewa published a study describing the first-ever observations of hagfish exploiting those glands to ward off predators. He analyzed 500 hours of video from cameras placed in deep waters off the New Zealand coast and found 14 encounters between hagfish and fierce hunters like the seal shark and the conger eel. In every case the hagfish emerged unharmed while the predators fled the scene, gagging on the irritating slime that rapidly expands in seawater and clogs the gills. “It was striking how effective this defense mechanism was,” Zintzen says.

The videos also reveal that at least one species of hagfish can go on the attack. Zintzen watched, mesmerized, as a hagfish chased a six-inch-long fish into a burrow, twisted its body into a knot for leverage, and slowly pulled the fish out—perhaps with the aid of a little slime. “They are fantastic animals,” Zintzen says. “But most probably you need to be a scientist—and a somewhat strange one—to love them.”

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