George Uetz is a behavioral ecologist and is interested in questions about both the proximate and ultimate mechanisms involved in animal communication and social behavior. The focus of his research is the behavioral ecology of spiders – in particular, the sensory ecology of multimodal communication, species recognition and mate choice in wolf spiders (Lycosidae). My research has been supported by the National Science Foundation and has been featured in print and electronic media around the world.
“Musical” probably isn’t the first word to come to most people’s minds when they think of spiders. And it’s true; as spiders don’t usually make airborne sounds. But it turns out there’s one type of wolf spider that’s a much better “singer” than many people realize. In fact, Gladicosa gulosa has a means of sound production that could provide insight into the evolution of sound-based communication.
This particular wolf spider has been called the “purring spider” for its unique courtship sound. When a male spider courts a female, he’ll use a special part of his body – legs called pedipalps – to create a vibration on the surface where he’s perched – such as a leaf. As Gladicosa vibrations are more powerful than other species, this results in an audible “purring” sound.
But it’s not necessarily the sound that attracts the females; it’s the vibration. Even though spiders can’t hear in the way we do, they are very good at detecting vibration. There are special sensory organs in their legs that allow them to “hear” vibration. So when a female on a different leaf picks up a vibration that’s being transmitted through the air, she knows there’s a potential mate nearby.
My student Alex Sweger and I tested this in the lab and found that this spider version of a serenade is very dependent on the surface where the spiders stand. Sturdier substances such as wood or rock won’t vibrate as well as a leaf or a piece of paper, so little – if any – sound is made. In a way, the leaves function almost like a loudspeaker and a microphone for courting spiders, sending and receiving airborne signals.
Most spiders use their ability to sense vibration as a survival skill – to find prey or avoid predators. But we’re studying how wolf spiders have adapted that into a means of communicating with their own kind.