Men spider wolves (Schizocosis stridulance), who improvise complex dance moves, are big winners in the mating game, courting females with routine action that stops the show. Now a new study finds that the more complex the dance, the more likely spiders are to find love.
Researchers have found that improvised steps benefit spiders that live in humid, mostly forested areas around the world. The ability to overcome a complex gait is not related to size or strength in men, but may suggest to women that the man has a certain athleticism and grace.
“Women are not necessarily looking for the biggest man or the noisiest man or the strongest man,” said 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 man who’s really athletic and can coordinate all these different signals in one display.”
Feel the noise
S. stridulans are brownish-gray spiders that can grow up to 1.4 inches (35 millimeters) in body length. But behind this gray color hides a screaming and bright performer, with mating dances that involve men patting their front legs and vibrating their bellies. The females sense these vibrations and decide whether to let the suitor get close enough to mate.
Former UNL PhD student Nuri Choi, a Hebets student, wondered what exactly women found so intriguing about their partners that they eventually chose. He analyzed one of Hebbets’ experiments in which ready-to-mate female spiders were placed in a soundproof chamber with a male in love at once. 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 flicker and tremor caused by the man’s dance.
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Of the 44 hopeful males, nine spiders were considered acceptable by the test females. The spiders that mated successfully had the most sophisticated dances, Choi found.
Entering the groove
Choi analyzed the complexity of spider dances with computer analysis, which was used to quantify the complexity of models in data signals as part of the data compression process. These methods have never before been applied to arachnid vibrations. Previously, Hebbets said, scientists looked at the characteristics of spider dance individually, focusing only on factors such as vibration, or looking at many basic interactions, such as those between visual cues and vibration.
“Right now, with some really talented people who have quantitative skills, come up with computational ways to look at how all these things can interact and how the whole package can be important in ways we would never know if you just we are looking at components A, B or C, “Hebets said.
Males danced more sophisticatedly for heavier females who are desirable mates because they are likely to be able to tolerate and care for large spider bites, the researchers found. Successful men also increased their dance complexity as courtship continued – dancing can last up to 45 minutes – which may indicate that women are expressing their interest in some way.
“When you talk about spiders,” Hebbets said, “I think that’s something people are reluctant to appreciate; that signaling devices pay attention to receivers, pay attention to their environment and adapt accordingly “
The complexity of the movements of these spiders is equivalent to a person dancing to a syncopated rhythm, changing the tempo or otherwise making unpredictable artistic choices. These movements do not correlate with the size of the spider or the ability of the man to produce strong vibrations, the researchers said on May 18 in the journal Biological letters (opens in a new tab). Instead, important qualities seem to be related to energy and skill, the researchers said.
Or maybe these men just stood out from the crowd, abandoning pre-planned choreography and thinking on their feet.
“There are a lot of studies that show that animals prefer novelties, in a sense,” Hebets said. In the case of wolf spiders in love, “men who are constantly changing things” may be the best way to get – and hold – women’s attention, she added.
Originally published in Live Science.