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.
Credit: http://bit.ly/12h5Smc 

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.

Here's what I was looking for. 

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 plants, plants recruiting help from insects, insects 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?

We're Jammin'

Aircraft and treehoppers communicate and surprisingly similar ways.

As I write this, I am several thousand feet above the Great Plains on my way to Seattle. In Kansas City, before we took off we were reminded that voice phone calls, AM/FM radio, Bluetooth, and all other methods remote communication are prohibited during flight. If I were to try to make a phone call, it could interrupt or ‘jam’ communications in the cockpit and put the flight in danger.

Imagine you are the pilot of a plane. Ordinarily, you’d be given coordinates, a route to follow and a schedule to guide your flight. Easy.

But this is no ordinary flight. This is a race, a mission that could mean death for all your passengers if you fail to land before you run out of fuel.

The only problem is, every airport has just one runway and only one plane can land at each one. If all the planes in the air make it to the airports before you do your passengers are toast. No problem though, if you know where you’re going you’re good to go, right?

Oh wait, did I say there was only one problem? I forgot a bit of important information.

You don’t have a schedule. You don’t have any coordinates. You don’t have a flight plan. You don’t even know where you’re going; you just know you need to get to an airport before your competitors. All you have is an FM radio and a password that will give you access to hints about the locations of nearby airports.

All other planes have the same passcode, a sort of key, and if any one of you gets near enough to an airport to transmit the full code, the air controllers at vacant airports will relay a bit of information about their location.

As I cross over the Rockies and we hit a bit of turbulence, lets shift gears for a second.

You’re not a frantic pilot navigating high above the clouds anymore; you are a little black insect (barely an 8^th of an inch long) called a treehopper, on a plant somewhere in the underbrush of mid-Missouri. Relieving, eh? Don’t get too comfortable.

Turns out you’re competing in a desperate race too. You need to find a female before other males mate with them all. But you don’t know where all these girls are. Luckily you’re equipped with an advertisement signal that lets females know you’re nearby and looking for some fun.

Ok, let’s zoom out and pan up about 10,000 feet to our frightened pilot again. Everything hinges on his ability to transmit his passcode effectively and use the info the airports send you from the ground.

Like any other password, this code is pretty specific. If you don’t transmit it  correctly, or if there’s any interference, airports won’t recognize it and you’re still flying blind. Being the clever pilot you are, you’ve found a way to use this to your advantage. You see, in this race all planes use the same radio frequency, so you can listen in other planes activities and disrupt or ‘jam’ their signals when they try to communicate with air controllers on the ground.

But you’ve got even more tricks up your sleeves. Jamming others isn’t always the best choice. Remember that you can listen in on what other pilots are saying to the ground and vice versa. Eavesdropping on these exchanges allows you to get the same directional information as you would if you were the one signaling to the females—I mean airport. 

Alright awesome, looks like you’ve outwitted all the other pilots in the air, you clever dog you. Yeah, I’m not fooling you anymore, you know what’s coming; there’s another catch.

You’re not the only crafty pilot out there, others have figured out the same trick and they’re jamming your transmission too!

Up in the big sky, my flight has almost made it across the Big Sky State, the turbulence seems to have cleared up, the incredibly persistent man in front of me has FINALLY given up on that damn crossword puzzle and my mind turns back to treehoppers.

Treehoppers communicate neither with radio waves as our airplane pilot does, nor with sound waves as their obnoxious relatives cicadas do. Instead, they use special drum-like organs to vibrate the stem they are on. This means they can all be thought of as communicating on the same ‘channel.’ So just like our pilot, our male treehopper can eavesdrop on his rivals and their airport—I mean females.

Since treehoppers must be still and silent to sense of male and female signals, both jamming and eavesdropping cost them some time, the most precious commodity in this race to mate. So as a male treehopper, you’ve got some decisions to make. Should you commit yourself to disrupting other males’ signals? Or perhaps just signal to females, ignoring other males? Or should you sneak around, never signaling but using the information from females’ responses to other males? Should you stop to jam or just keep moving, getting ahead in the race while your enemy gets free hints?

Those are the questions that my lab is trying to answer. What influences these complex choices in these tiny insects with pin-sized brains?

Whatever they’re doing, it seems to be working. Males find females. Some are better than others. The strategies that work get passed on to future generations of treehoppers and the bad tactics disappear. In age when information makes the money flow, science move, military regimes rise and fall, makes the world go round, understanding data and communication is not just important; it’s inseparable from every aspect of modern human society. Understanding how nature solves such seemingly artificial situations is truly enlightening.

Alright, enough musing. We’re flying past Mt. Rainier, a solid mountain erupting out of a sea of vaporous cloud mountains, and the pilot says I need to turn off my laptop and the music I’ve been jammin’ to.
           

Hey, I’m not mad though, I’m just thankful we found our airport ok.