National Geographic News
A photo of a fishing spider with fish prey.

A fishing spider in French Guiana clutches its prey.

PHOTOGRAPH BY INGO ARNDT, NATURE PICTURE LIBRARY/CORBIS

Katie Langin

National Geographic

Published June 18, 2014

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," said Marie 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."

How It's Done

Fish-eating spiders live in freshwater environments like ponds and wetlands, where they hunt for meals on foot instead of using a web. Some can even swim, dive, and walk on the water's surface (see video below).

Footage of fishing spiders stalking and eating their prey.

 

These semiaquatic spiders "anchor their hind legs to a stone or a plant, with their front legs resting on the surface of the water," the authors write. Then the arachnids wait to ambush their prey. The slightest ripple in the water, or anything that touches the spiders' outstretched legs, can trigger an attack.

That's because fish-eating spiders are generalist predators—they'll go for nearly anything that moves. Most of the time, that means their meals are insects that have fallen into the water. But occasionally they purposely attack larger animals like fish.

And they're well equipped to eat them, with mouths that can pierce flesh. They use those mighty maws to inject a lethal venom packed with powerful neurotoxins—chemicals that attack the nervous system—into their fish prey.

When the fish is dead, the spiders haul it to dry ground and administer chemicals that liquify its body tissues, making the meal easier to eat. (Related: "Male Spiders Self-Sacrifice, Lose Genitals.")

Outsize Accomplishment

In the animal world, the average predator is 42 times larger than the prey it's trying to subdue. Some fish-eating spiders, however, are actually smaller than their prey. (Watch videos of spiders catching bats, frogs, and mice.)

The authors speculate, for instance, that a giant fishing spider—weighing in at 7 grams (0.4 ounces)—would be capable of catching a 30-gram (1 ounce) fish.

Such supersize food sources could be critically important for females in the process of producing eggs, or for spiders that don't have access to enough insect meals.

One thing is for sure: It's more bad news for little fish.

Follow Katie Langin on Twitter.

8 comments
Mark River
Mark River

I've seen spiders on the edge of sandbars on the lower Mississippi River. They were probably fishing

Ludo Gone Fishin
Ludo Gone Fishin

Incredible, nature is awesome and fairly dangerous sometimes.

Thomas Cassar
Thomas Cassar

Arthropods never cease to amaze me with their astounding strategies for survival. A truly great article.

Share

Feed the World

  • How to Feed Our Growing Planet

    How to Feed Our Growing Planet

    National Geographic explores how we can feed the growing population without overwhelming the planet in our food series.

See blogs, stories, photos, and news »

Latest From Nat Geo

See more photos »

Shop Our Space Collection

  • Be the First to Own <i>Cosmos: A Spacetime Odyssey</i>

    Be the First to Own Cosmos: A Spacetime Odyssey

    The updated companion book to Carl Sagan's Cosmos, featuring a new forward by Neil deGrasse Tyson is now available. Proceeds support our mission programs, which protect species, habitats, and cultures.

Shop Now »