Jumping spiders can hear sounds from as far as 10 feet away. Photo by Gil Menda and the Hoy lab
ITHACA, N.Y., Oct. 13 (UPI) -- Spiders don't hear like mammals do, but they can sense vibrations through the air. Until now, scientists thought arachnids could only sense vibrations from a couple of inches away.
New research proves a jumping spider's aural range extends several feet. It's likely other spiders can perceive vibrations from considerable distances, too.
"The sensory world of the tiny jumping spider was thought to be dominated by sight and tactile touch," researcher Paul Shamble said in a news release. "Surprisingly, we found that they also possess an acute sense of hearing. 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."
Shamble and research partner Gil Menda discovered the surprisingly large aural range by accident while working in Ron Hoy's lab at Cornell University. Shamble and Menda were perfecting a new method for measuring the jumping spider's brain activity during visual processing.
One day, when Menda dragged a chair across the lab floor, creating a squeaking noise, researchers heard a series popping sounds emanating from their newly developed brain sensor. They had programmed their device to make sound effects when the spider's neurons fired. The sound of the chair had excited a deep portion of the jumping spider's brain.
"We started discussing the details about how spiders can only hear things close by and, to demonstrate, Paul clapped his hands close to the spider and the neuron fired, as expected," Menda explained. "He then backed up a bit and clapped again, and again the neuron fired."
Further testing showed jumping spiders are best able to hear frequencies similar to those created by the beating wings of parasitoid wasp enemies. Sounds from as far away as 10 feet excited the auditory neurons in the spider's brain. Researchers were also able to stimulate the same neurons by touching the hairs on the spider's legs.
"We found that when we shook single sensory hairs back and forth -- these are the same hairs that are known to respond to sounds originating close to the animal -- we also got responses," Shamble said. "This suggests that these hairs are how spiders are registering far-away sounds."
The researchers published their findings in the journal Current Biology.