Monday, July 1, 2013

Eavesdropping on a Silent Symphony

This morning I heard things that no one else on earth has ever heard. Would you like a listen?

Micah Fletcher at Hinkson Creek in Columbia, Missouri
Credit: Rex Cocroft
I woke up at 6:30 on a Sunday morning, grabbed a bite to eat and headed over to the greenhouse to get my equipment. I was on a mission to record some music. But this is no ordinary music.

As the morning rolled on, the wind was picking up. Time was of the essence; I needed to get to that grass before the late morning breeze ruined all hopes of success.
Vibration recording setup 
with phono cartridge on a tripod (left),
 DI box and headphones (center),
 and recorder (right) 
Credit: Micah Fletcher

Finally, I waded through some brush, scrambled down the creek bank and came upon a lush patch of tall green grass on the edge of Hinkson Creek. I opened my pack and started to assemble my mobile studio. It’s a modest, homemade setup: a phono cartridge like what you’d find on a vinyl record player, a DI box that you might use to help record an electric guitar, and a simple recording device similar to the classic tape recorder except with a memory card instead of a cassette.

Careful not to disturb the rest of the vegetation or step too heavily on the surrounding rocky soil, I put my headphones on, gently (oh, so gently) placed the needle of the phono cartridge against a blade of grass, turned up the volume and listened.

You see, I was listening in on a silent symphony. Hundreds of insects call this patch of grass home, and most of them have something to say. Yet unlike songbirds, they don't produce signals that the human ear can detect. 

Instead, they rely on vibrational communication. They tap, drum, and shake the stems or leaves they are on to signal to other insects. As I showcased in a previous post, “We’re Jammin,’” this often-overlooked and little-overheard method of communication can be even more complex than the more well known auditory calls of other insects.

Like any good science, my eavesdropping had a purpose, a goal. I was searching for a specific insect species. 
Leafhoppers on maize.
Perhaps  my evasive signaler
looks something like these guys.

Months earlier, my lab had recorded this individual without identifying the species, but we ended up using the recording in a research paper so we want to back track and find the bug again so we can be as specific as possible.

No, this is not some alien transmission spelling the dimise of the human race. Nor are you having a flashback to the days of dialup internet.  This is an insect singing "We've come too far to give up who we are, so let's raise the bar and our cups to the stars," on a blade of grass.

Yet like any good science, things didn't go exactly as I'd planned; I opened doors to more questions than I answered. I never found the mystery insect, but between the cacophonous rubbing and bumping of grass blades in the breeze, I heard an ant scuttling within millimeters of my phono cartridge needle, I heard this signal from some unknown bug, and this mysterious droning signal. You and I are some of the first people to hear these particular insects.
Phono cartidge attached to
a blade of grass
Credit: Micah Fletcher

Aside from the ant (who in technical terminology was just making "noise"and not "signaling"), I did not see any of the creatures that were producing these diverse vibrations. They are so small and the grass is so intertwined that it is extremely difficult, sometimes impossible, to tell who is talking unless somebody moves. 

Keep in mind that I can't reach into the grass and clear away blades to get a closer look; that would only cause a deafening crash of leaves that would silence my frightened anonymous signalers.

Part of what makes us human is our unending curiosity about the unknown. Throughout our history we've been fascinated by the stars, other humans and big charismatic animals around us. But take that curiosity one step further, look down at where you're stepping and you'll witness plants talking to other plantsplants recruiting help from insectsinsects manipulating plants into building homes, and insects using plants to transmit vibrations to other insects. THAT'S what's really mind blowing.

So if you have some headphones, or some decent speakers and quiet room, take a moment to close your eyes. Imagine you're just a few millimeters tall, clinging to a blade of grass along the edge of Hinkson Creek. If your sense of touch was finely tuned, you'd hear this: a secret silent symphony in the alien world that lies right under our noses.

A spectrogram of the final linked recording. Can you pick out the different signals as you listen?