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These Beetles are Making a New Kind of Sound

Tropisternus_blatchleyi_2_0.JPG
user Fredlyfish4, via Wikimedia Commons
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At some point, many of us have taken time to just sit down and listen to the birds sing. Ornithologists and avid listeners can usually identify birds just by their calls. MSU Biology professor Michael Flinn and former grad student Nissa Rudh are trying to ID something a little different.

The results look -and sound- quite like nothing you’ve heard before.

 

110405-000_Hydrophilid_Stridulation.mp3
This is the call of a beetle from the Hydrophilidae family, more specifically the Tropisternus genus. (Audio courtesy of Dr. Michael Flinn)

Flinn and Rudh are identifying beetles based solely on the sounds they make.

They’ve been out recording in several locations, most recently a pond in Hancock County.

Flinn says a short clip and a computer are all they need to know exactly what kind of specimen they’re looking at.

Using traditional methods, you’d have to dig out an identification guide and listen closely for specific features of that sound until you found a match.

“Basically what we’re able to do is narrow it down to a couple species or a species-specific call for each one," Flinn said.

They're using what looks like a regular microphone to record the calls, but it’s actually a specially designed hydrophone to pick up the slightest of sounds from a few meters away underwater.  

Rudh says certain beetles make these noises by rubbing a bumpy surface of their body.

“They make them for a disturbance call so if you pick them up - right now you could go out to the pond and find one of these and pick it up, and it would make these little scraping sounds," Rudh said.

"It’s almost like a little 'buzz buzz buzz'."

From there, a computer program processes the audio to narrowly identify the insect's species.

256px-Underwater-microphone_hg_1.jpg
Credit Hannes Grobe/Alfred Wegener Institute for Polar and Marine Research, Bremerhaven, Germany, via Wikimedia Commons
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This is a hydrophone. The bottom end is the receiver; it picks up vibrations underwater and converts them into a signal we can hear.

Rudh says the concept was fairly new.

“No one’s really done this before. It’s been done with birds and with grasshoppers and insects on the land. but it’s kind of new to an aquatic environment," Rudh said.

"People knew that insects made sounds underwater, but no one has been utilizing this."

The research started out small just a couple years ago.

“It started out with me just going into the swamps, the streams and the lakes trying to find anything that would make a noise," Rudh said.

From there, she took the research further.

After finding success recording in just a small Styrofoam bucket, the project ramped up to a water-filled cattle tank.

The research peaked with extensive testing at local ponds, where the sensitive hydrophones would work without too much interference.

Flinn says this new electronic method is much more efficient than the old school process of identification by hand. It also brings some environmental benefits.

“I would go out there with a big net and I would rake that net through the vegetation and through everything and I would dump it out in a pan and bring it back here, preserve it all and work through and identify everything," Flinn said.

"One interesting thing is, say for example, you had an endangered species or something like that. You don’t want to go out there and destroy its habitat looking for it."

Rudh and Flinn are currently working to get their research published, something they believe could fundamentally change how we look at insects both in our region and abroad.

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