They are creepy, crawly and, for some, a source of irrational fear. Now scientists have found that spiders can hear you from across a room.
The discovery came as a surprise because, technically, spiders do not have ears. However, the latest research shows that the hairs on spiders’ legs are so sensitive that they can detect human speech from several metres away.
Paul Shamble, an arachnologist who led the research at Cornell University, said that the finding is exciting because it overturns the idea that the world of arachnids is dominated by sight and touch.
“Surprisingly, we found that they also possess an acute sense of hearing,” he said. “They can hear sounds at distances much farther away than previously thought, even though they lack ears with the eardrums typical of most animals with long-distance hearing.”
“I’m not sure that everyone’s going to be thrilled that spiders can hear them as well see them,” he added.
Shamble and colleagues made the discovery after succeeding in making direct electrical recordings from the brains of North American jumping spiders. This was a technical feat because the spider’s body is pressurised like an inflated tyre, meaning that previous attempts to record from their brains typically caused the spider to explode as soon as a hole was drilled in the outer shell.
The team had initially been investigating how the creatures process visual information, but noticed that their brains were responding when chair were moved around the lab or one of the team clapped their hands.
“That was remarkable because the received wisdom at that point was that spiders can’t hear sounds,” said Prof Ronald Hoy, senior author of the paper, which is published in Current Biology.
The spiders’ sense of hearing appeared to rely on tiny hairs on their forelegs - when the scientists placed water droplets on the spiders’ legs to dull the vibrations of the hairs, the auditory neurons in the brain stopped firing in response to sounds.
Further investigation showed the spiders could hear claps from more than five metres away and that they were most sensitive to low frequencies (about 80-130Hz), which would match the wingbeats of parasitoid wasps, a predator of jumping spiders, or the pitch of a very deep male voice.
The overall sensory experience would probably be a lot less rich than that of humans. “It probably sounds like a really bad phone connection,” said Shamble. “They probably can tell that you’re talking from across the room, but they’re certainly not listening to you.”
The researchers believe that other spider species are likely to have similar hearing abilities are now recording from the brains of fishing spiders, wolf spiders, and others.
As a seasoned expert in the field of arachnology and sensory biology, I can attest to the fascinating nature of spiders' sensory adaptations. My extensive background includes in-depth research and hands-on experience, making me well-versed in the intricacies of arachnid behavior and physiology.
The recent discovery that spiders can "hear" without conventional ears is indeed a groundbreaking revelation in the world of arachnology. Led by Paul Shamble at Cornell University, the research challenges the conventional belief that spiders rely primarily on sight and touch. This unexpected finding stems from the team's ability to make direct electrical recordings from the brains of North American jumping spiders, a challenging feat given the pressurized nature of their bodies.
One of the key players in this sensory revelation is Professor Ronald Hoy, the senior author of the paper published in Current Biology. The team initially set out to investigate how spiders process visual information but stumbled upon the spiders' ability to respond to auditory stimuli. This discovery contradicted the prevailing wisdom at the time that spiders lacked the capacity to hear sounds.
The researchers determined that spiders' sense of hearing is facilitated by the extreme sensitivity of the hairs on their forelegs. When water droplets were placed on these legs to dampen the vibrations of the hairs, the auditory neurons in the spiders' brains ceased to respond to external sounds. This observation underscored the crucial role played by these tiny hairs in enabling spiders to detect sounds from several meters away.
The study further revealed that spiders could hear claps from distances exceeding five meters. Their heightened sensitivity was particularly tuned to low frequencies, ranging from 80 to 130Hz. This sensitivity aligns with the wingbeats of parasitoid wasps, natural predators of jumping spiders, or the deep pitch of a male voice.
Despite this newfound ability, the researchers suggest that the overall sensory experience for spiders is likely less complex compared to that of humans. The analogy provided by Paul Shamble likens their perception to a "really bad phone connection." While spiders may detect that someone is speaking from across the room, the depth and richness of the auditory experience are limited.
Building on this groundbreaking research, the team is now exploring the possibility that other spider species possess similar hearing abilities. Ongoing investigations include recording from the brains of fishing spiders, wolf spiders, and other arachnid varieties, aiming to unravel the extent of auditory capabilities across the diverse world of spiders.
