Masculine wolf spiders (Schizocosa stridulans) that improvise intricate dance moves are big winners in mating play, courting females with breathtaking tap routines. Now, new research has found that the more complex the dance, the more likely spiders are to find love.
The study’s researchers found that improvised steps benefited the spiders, which live in humid, mostly forested areas around the world. The ability to master an intricate movement has not been associated with size or strength in men, but for women it may indicate that the man possesses a certain athleticism and grace.
“Women aren’t necessarily looking for the tallest man, the loudest man, or the strongest man,” says study co-author Eileen Hebets, a biologist at the University of Nebraska-Lincoln (UNL). said in a statement. “But maybe they’re looking for a guy who’s really athletic and can coordinate all these different signals into one display.”
feel the noise
S. stridulans are brownish-grey spiders that can reach a body length of 35 millimeters. But behind that drab coloring hides a flashy and flamboyant performer, with mating dances in which males tap their front legs and vibrate their bellies. Females sense these vibrations and decide whether to let the suitor close enough to mate.
New UNL graduate student Noori Choi, a student of Hebets, wondered what exactly females found so fascinating about the mates they eventually chose. He analyzed one of Hebet’s experiments, in which mate-ready female spiders were placed in a soundproof chamber, each with an enamored male. The researchers placed the spiders on thin filter paper that easily transmits vibrations and monitored them with cameras and a laser to detect every last quiver and twitch caused by the male’s dance.
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Of 44 hopeful males, nine spiders were deemed acceptable by the female testers. The spiders that successfully mated also had the most complex dances, Choi found.
Get into a groove
Choi analyzed the complexity of the spider dances using computational analysis used to quantify the complexity of patterns in data signals that are part of the process of data compression. These methods have never been applied to arachnid vibrations before. Previously, Hebets says, scientists have looked at the characteristics of a spider’s dance individually, just focusing on factors like vibration alone, or they’ve looked at very basic interactions, like that between visual cues and vibrations.
“Now we’ve gotten to the point, with some really talented people with quantitative skills, of finding computational ways to look at how all of these things might interact and how the whole package might matter in a way we never would have understood, whether we only looked at components A, B or C,” Hebets said.
Males danced with more complexity for heavier females, which are desirable mates because they are likely capable of carrying and caring for large broods of spiders, the researchers found. Successful males also increased their dance complexity over the course of courtship—dances can last up to 45 minutes—which may indicate that the females were expressing interest in some way.
“If you’re talking about spiders,” Hebets said, “I think that’s something that people don’t appreciate; that signalers are aware of the receivers, they’re aware of their surroundings and adapt accordingly.”
The complexity of these spiders’ movements is analogous to a person dancing to a syncopated beat, increasing the tempo, or otherwise making unpredictable artistic decisions. These movements did not correlate with spider size or a male’s ability to produce loud vibrations, the researchers reported May 18 in the journal biology letters (opens in new tab). Instead, the important traits appeared to be related to strength and dexterity, the researchers said.
Or maybe these men just stood out from the crowd by abandoning pre-planned choreographies and thinking spontaneously.
“There are many studies that show that animals prefer novelty in some ways,” Hebets said. In the case of wolf spiders in love, “the males who are constantly changing things up” might be the best way to attract — and keep — females’ attention,” she added.
Originally published on Live Science.
https://www.livescience.com/male-wolf-spiders-complex-dances Male spiders drum out mesmerizing syncopated beats to woo mates