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Study: Spiders eavesdrop to gain edge on sexual competition

"This discovery has completely changed our way of thinking about this little spider," said researcher George Uetz.

By Brooks Hays

CINCINNATI, Aug. 4 (UPI) -- Spiders make pretty good spies. According to new research, male spiders regularly eavesdrop on their sexual rivals in order gain a competitive edge.

The new study, published in the journal Animal Behaviour, shows that spiders are able to recognize and learn the visual cues that land their competitors a mate.

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A group of scientists -- from Alma College, The Ohio State University at Newark and the University of Cincinnati -- were able to confirm this unique phenomenon by raising a group of male wolf spiders in isolation, and then attempting to teach them the subtleties of the species' mating rituals.

In the wild, wolf spiders know a female is ready to reproduce when she puts out a perfume-like pheromone. Males begin the mating process by coaxing the female to breed with a series of leg-taps.

When shown a series of videos revealing spider leg-tapping in action, the captive wolf spiders were able to pick up the technique in just four days.

Having witnessed the ritual performed in the presence of a female spider, the specimens soon began attempting courtship on their own.

"This discovery has completely changed our way of thinking about this little spider," researcher George Uetz, a professor of biological sciences University of Cincinnati, said in a press release. "We thought because they were invertebrates with a tiny brain, everything about them is genetically regulated in a hardwired nervous system."

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"Over the years, we've found there's a lot more to the story," Uetz explained. "Males learn to associate the courtship behavior of other males with female cues and they can make this leap. It's a complex set of behaviors for a tiny little brain. Not only do they learn from visual cues but also from vibration cues."

Uetz says that eavesdropping is common in nature, but is a behavior one expects to see in birds, fish and mammals -- not usually invertebrates. More and more, however, scientists are realizing they've underestimated the spider.

Scientists say that eavesdropping on the right spider and learning the right dance can be a matter of life or death. Males that don't replicate the proper leg-tapping rhythm are at risk of being devoured by their would-be mate. Even when males flirt properly, they're not necessarily safe. Researchers say about 12 percent of males are eaten post-coitus.

"Courting in response to other males' signals is not without risks to the eavesdroppers," said researcher David Clark, a professor of biology at Alma College. "The conspicuous courtship signals intended for females may also make males more visible to predators, like toads or birds searching for their next meal."

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