Fish-Eating Spiders Can Catch Prey 5 Times Their Size

[Arosa Hya]

A fishing spider in French Guiana clutches its prey.

PHOTOGRAPH BY INGO ARNDT, NATURE PICTURE LIBRARY/CORBIS


It isn't easy being a little fish. Predators dart at them underwater. Humans try to snare them with hooks. And other species—more than we'd thought, it turns out—can pounce on them from above.




According to a new study, spiders in 8 of the world's 109 arachnid families can catch and consume small fish. Some of them can even subdue fish five times heavier than they are.

These arachnids are nearly everywhere. The study, published June 18 in the journal PLOS ONE, says fish-eating spiders can be found on every continent except Antarctica. They're especially prevalent in warm, oxygen-depleted bodies of water like the wetlands of Florida, where fish are more likely to come to the surface in search of oxygen-rich water.

At least 18 species have now been observed catching fish, including six-spotted fishing spiders (Dolomedes triton) in the United States, pond wolf spiders (Pardosa peudoannulata) in India, and great raft spiders(Dolomedes plantarius) in the United Kingdom.

These findings were pieced together by Martin Nyffeler at the University of Basel, Switzerland, and Bradley Pusey at the University of Western Australia in Albany. The two biologists first searched for published reports and Internet posts documenting spiders eating fish. What they found—89 records in total, half of which hadn't been published in the scientific literature previously—allowed them to paint a more complete picture of this unusual behavior.

"Fish predation by spiders has always been seen as a bit of an oddity," saidMarie Herberstein, an expert on spider behavior at Macquarie University in Sydney, Australia, who was not involved in the study. "But the review makes a compelling argument that it is widespread, both taxonomically as well as geographically. This was certainly a surprise."