Karen Hopkins: This is Scientific American’s 60 Second Science. I’m Karen Hopkins.
Some things are SO adorable, we say they’re cute as a bug’s ear. Of course, insects don’t have ears. But a new study shows that orb-weaving spiders can use their webs to detect sounds. the findings unfold in the Proceedings of the National Academy of Sciences.
RonHoy: Any animal that makes sounds probably has an ear.
Hopkins: rum today studies neurobiology and behavior at Cornell University in Ithaca.
Hears: …from tiny crickets and flies that are even smaller than crickets, to humans of course.
Ron Miles: It is also quite interesting that many animals do not have eardrums. But they still listen.
Hopkins: that’s rum miles.
Miles: The two Rons, here.
Hopkins: Ron Mileswho has been collaborating with Ron Hears for 30 years, he’s an engineer at Binghamton University…
Miles: …an hour’s drive from Cornell.
Hopkins: Bugs that lack eardrums receive audio input with very fine hairs.
Miles: If you look at spiders and insects, they are covered in hair.
Hopkins: Because these little rustling filaments can float freely in the breeze, they are excellent at detecting the air currents that make up sound waves.
Miles: Since we knew that so many animals like small insects and spiders have hairs that can sense sound… we wondered how they would make something that could sense sound the way some of these little animals do.
Hopkins: One possibility arose during an afternoon walk.
Miles: My graduate student, Jian Zhou, was walking in our campus nature reserve one day and noticed that when the wind is blowing, if you look at a spider web, it moves with the wind. And he thought that maybe a fine cobweb or spider silk could act as a sound sensor.
Hopkins: To find out, the researchers persuaded a spider to give them some silk…
Miles: …and we played sound on a tiny strand of spider silk and found that when the silk is very thin, it moves with the air in a sound field surprisingly well…over a wide range of frequencies, from 1Hz to 50khz. So we knew that spider silk was some kind of ideal and perfect sound sensor.
Hopkins: That was eye-opening for the researchers… but does it tickle spiders?
Miles: So we set out to try to find out if spiders could actually hear sound using their web. And this was a difficult question to answer.
Hopkins: For one thing, they had to find a way to get an entire spider web into the special soundproof chamber in the basement of the lab building.
Miles: You know, spider webs are very delicate. You can’t go out into the woods and find a spider web, grab it and take it home. It is attached to things. And it is not easy to get it intact.
Hopkins: Especially the ones made by industrious orb weavers… spiders like the title character in Charlotte’s Web.
Hears: We are talking about a pretty spectacular website. It’s this wheel-shaped network that’s around upstate New York… if you walk through any field, you’re going to go through one or see one and avoid it because they’re big. It can become as large as a yard or a meter wide.
Hopkins: So Jian Zhou and his fellow student Junpeng Lai came up with a way to customize the nets to size.
Miles: What they did was they made a little wooden frame… about the size of a decent sized picture frame… and they put this frame on the windows of our building.
Hopkins: The lights in the building attracted insects… and the insects attracted spiders.
Miles: So… the spiders built their webs on the frames. Then in the morning my students would go and pick up the frames and basically kidnap the spiders and take them and put the frame in the… chamber intact.
Hopkins: Now, how can you tell if a spider web works like a spider hearing aid? One way is to monitor the spider’s brain.
Hears: My lab, the neurophysiologists, did some recordings of the sensory system of the nervous system that showed that you do indeed get an acoustic response in the nerves to sound… coming from a speaker a little over a meter away.
Hopkins: But even more revealing was how the spiders acted.
Hears: To very loud sounds, you might get a loud response…the spider would flatten or crouch. But he really is ducking. that is indicative [to a biologist] of an alarm response.
Hopkins: And when serenaded with sounds that are maybe 10 decibels or 100 times softer…
Hears: Without changing his body posture or making any other movements, he could simply lift his two front legs out of the net.
Hopkins: That leg lift, says Hoy…
Hears: …it’s a spidery way of maybe putting in two more sensors to see what’s coming. We do not know yet. But that response to a very mild stimulus could simply be the spider’s reaction to, “I know there’s something out there, I heard it, but I need more information.” So… that’s essentially the proof that was needed to show that spiders can hear sound.
Hopkins: This stringy approach to acoustics could one day change the way we make microphones…and take webcast to a whole new level.
For Scientific American’s 60 Second Science, I’m Karen Hopkin.
[The above text is a transcript of this podcast.]