For the longest time, scientists have thought that spiders only rely on vision and vibrations when detecting movement. A new study, however, proves this as false.
This isn't to say that spiders couldn't hear anything at all. They can, but are only able to pick up sound that's within three feet of their body, according to CS Monitor.
Spiders Using Specialized Sensory Hairs To Hear Noises
The previous assumption was because the arachnids lack eardrums. Thus, the notion has always been concerned with how spiders can hear long distant noises if they lack crucial hearing faculties.
"The standard textbooks say that spiders are acutely sensitive to airborne vibrations from nearby sources, sounds about a body length or a few cm away," Gil Menda of Cornell University said.
"We have discovered that jumping spiders can hear things from much farther away than this. Interestingly, it seems that in both cases, this 'hearing' is accomplished by sensory hairs."
While jumping spiders are the only arachnid species involved in the study, researchers believe that its kin is likely to have the same auditory range as they too possess these specialized sensory hairs. Biologist Nathan Morehouse is also wondering if this hearing is being combined with surface vibrations by the spiders to complement each other.
"Loud sounds will travel through air, but may also create vibrations in things like leaves on the ground," Morehouse explains. "So in natural environments, these animals might respond to both airborne and vibrational aspects of loud sounds in their environment."
Scientists Admit That The Arachnid Discovery Happened By Luck
This auditory discovery was apparently discovered by happenstance, according to Research Gate. Scientists Gil Menda and Paul Shamble were conducting neural recordings of jumping spiders' brain to better understand how the arachnid process visual information.
"One day, Gil was setting up one of these experiments and started recording from an area deeper in the brain than we usually focused on," says Shamble. "As he moved away from the spider, his chair squeaked across the floor of the lab."
The neural recordings, explained Shambles, uses speakers so that they can hear when neurons are firing. When it does it makes a distinct "pop" sound.
When Menda's chair scraped the floor, the neurons started popping. Fascinated, he did it again and the same result occurred.
"Paul clapped his hands close to the spider and the neuron fired, as expected. He then backed up a bit and clapped again, and again the neuron fired. Soon, we were standing outside the recording room, about 3-5 meters from the spider, laughing together, as the neuron continued to respond to our clapping," said Mandela.
The scientists are marveling at this find since the jumping spider was able to do this even with such a small brain. "This study is going to motivate a bunch of research into the sonic world of these animals which hasn't really been done before," Morehouse said.
