Spiders are keeping loud noises out by using their webs in strange way

We all dust away cobwebs, but the structures serve a vital purpose for spiders to filter out loud ambient vibrations in urban environments, a new study published in the Current Biology journal has found.

Surrounding noises like construction or traffic are quietened by the spiderwebs so the arachnids can hear signals that are key to their survival.

Biologists at the University of Nebraska–Lincoln worked on this research, the first to show a species' response to man-made noise and how they've adapted to hear the necessary sound vibrations.

In the study, researchers Brandi Pessman and Eileen Hebets were able to prove that funnel-weaving spiders respond to surrounding noise by changing the way silk webs relay the vibrations, which act like external sensory extensions.

A key finding from the experiments was that a web communicates vibrations differently according to whether the spider that created the web came from a rural or urban area.

“One of the most interesting things that we found is that urban and rural spiders are reacting differently when they’re put into a noisy environment," said Pessman, a postdoctoral researcher in biological sciences and the lead author of the paper.

“This means that spiders with different experiences with noise – whether they themselves experienced it or their mothers passed it down to them across generations – respond differently.”

The experiment

iStockphoto by Getty Images

Over 60 Funnel-weaving spiders, also known as Agelenopsis pennsylvanica, from Lincoln, Nebraska, were used for this study, as this species heavily depends on vibratory signals to receive information.

Once in the lab, they then spun webs over four nights inside controlled environments - one quiet and one noisy. After this, the researchers then conducted test vibrations with the webs to see how the energy moved in each of the structures that were created in different conditions.

But what did they find? As a result of soundproofing their webs, fewer vibrations were transmitted to the city spiders - that's in order for them to be able to hear their prey while also not being overwhelmed by all the other noises that typically occur in urban environments.

Meanwhile, webs created by rural spiders were more sensitive to noise - similar to when you turn up the TV volume to hear better when everyone around you is talking.

“Rural spiders are not used to as much noise in their environment,” Pessman said. “When they suddenly get a lot of noise, they might try to ‘turn up’ the volume in their webs or amplify what’s coming in to better hear certain signals above the noise.”

What's next?

Now that we know how spiders are adapting their webs to noise, researchers will be looking to see the ways in which spiders are able to do this, such as changing the silk tension, altering the location or number of anchor points, or shaping to filter or boost particular frequencies.

Furthermore, videos of the webs being built will also help researchers understand the construction methods.

"This study really highlights the role of receivers in overcoming environmental noise,” said Hebets, professor of biological sciences at UNL.

“It opens up entirely new avenues of research. For example, are receivers placing themselves at certain locations in the environment where signals are going to receive less attenuation or overlap of noise?”

Elsewhere, scientists find 'giant' dinosaur spider fossil in Australia, and a Tarantula species spins sperm webs while wearing pink booties.

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