Fishing Isn’t Just for the Birds

When we talk about spiders' diets, we think of helpless insects ensnared in carefully spun webs. But larger spiders have a much more varied diet. They can eat small birds, baby rodents, lizards, frogs, and even fish. Scientists have known for sometime that spiders in the Florida wetlands have a predilection for small native fish species, but they had no idea that there were so many species of eight-legged pescatarians all over the world.

Martin Nyffeler, a biologist from the University of Basel in Switzerland, found that eighteen water-dwelling spiders species from five spider families, including fishing and nursery web spiders, go fishing. Most of these spiders regularly eat fish twice the size of their torsos—a lot like a person eating a whole pot-bellied pig. And here's the real surprise, these semi-aquatic species can be found on every continent, except Antarctica.

One interesting aspect of the study: spiders catch fish differently than they catch insects. Instead of spinning a web, they anchor their bodies to something—a rock or plant—and lie in wait. Hovering gently on the water's surface, waiting for an unsuspecting fish to swim below. When a fish swims close, they dive down and inject the fish with neurotoxins and enzymes that, as with insects, kill the fish and liquefy its innards. Then, it's feast time. The spider retreats to dry land to use its jaws and pedipalps to eat, or more accurately, drink the fishy soup.

The research suggests that fish probably provide important nutritional value to a spider's diet, but it's not yet clear what the actual benefits spiders reap from this aquatic treat. But even though we don't know why spiders nosh on fish, watching them hunt is itself a treat.

[video:216616|caption:Get a close up look at one spider catching a fish]