The study leaves a few key questions unanswered. That suggests this might be a communication style that's reserved for talking to females, but they don't know yet. When researchers just played the vibration sound, only females responded. Males could only make the vibrations when standing on paper, and females could only receive the signal when standing on paper. They found that the surface is key to the male's "purring" game. Using a special device, they were also able to convert the vibrations to audible sound, so here's what the direct vibrations themselves would sound like to us if we could hear them: In the lab, Sweger and Uetz recorded male spiders making the vibrations and sounds on different surfaces: paper, which can vibrate, and granite, which can't vibrate. When the sound waves hit those leaves, they vibrate, and the female picks up on the vibrations. That the sound of the vibrating leaf travels to other leaves where females stand. To the human ear, the sound of the vibrating leaf sounds like a low purr, quieter than a cricket: They rub the two limbs together to generate vibrations that hit nearby leaves. One has a rough tip, while the other is shaped for scraping. The spiders have specialized arm-like appendages called pedipalps, one on each side of the mouth.
That made them an intriguing group for Sweger and his advisor George Uetz to study. Other wolf spiders are known to produce vibrations to communicate, but those vibrations don't come with audible sounds. It's a bit of a roundabout way to flirt, but it could help researchers discern why some organisms communicate through sound, while others use vibrations. "They're courting on dead leaves, and that leaf itself is what's resulting in the airborne sound," Alexander Sweger, a biology grad student at the University of Cincinnati, told Live Science. Instead of using an organ to produce a sound, like crickets or katydids, the spiders vibrate inanimate objects around them. Leaves serve as a sort of telephone line or radio wave through which the spiders call females, and they're essential to the wold spider communication system, as researchers reported May 20 at the Acoustic Society of America's annual meeting in Pittsburgh. If it hits leaves near a female spider, causing them to vibrate, she can pick up on the vibrations.įor this to work, male and female spiders need to be on a good surface that can vibrate. The vibrating leave produces a low "purring" sound audible to humans, and that sound travels. Male spiders actually produce vibrations, which hit surrounding dried leaves and cause them to vibrate. Instead, the sounds are part of an elaborate communication system that male spiders use to woo females. However, wolf spiders don't have ears themselves - at least in the traditional sense. The right kind of "purr" makes a female wolf spider go weak at the joints.īiologists have known for awhile that wolf spiders ( Gladicosa gulosa) can make sounds that humans can hear, explains Laura Geggel for Live Science.
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