Bornean Frogs: Feelin' Ultrasonic

Apr 29 2009 Published by under Natural Sciences

So we b0rked the blog last night, but the wearing of sackcloth and ashes and the libations we have placed on the altar of the Overlords have gotten it fixed! I am eternally grateful.
And now, on to the science. Let's all feel supersonic together:

(oh yeah, Sci went there. Let's all be moody and wear our fake Beatles' glasses together, shall we)
Now let us all pause for a moment and be glad that there is no species that uses Oasis songs as its mating calls. Ok, there was a brief period in the 90's where the human species almost fell, but we hoisted ourselves back up again.
No, I can't think of any species that uses "Supersonic". But there ARE lots of species that use ULTRASONIC. Until now, interestingly, those species of animals using ultrasonic communication didn't include frogs, really. Until now. Arch et al. "Pure ultrasonic communication in an endemic Bornean Frog." PLoS ONE, 2009.

What you're looking at up there is Hula cavitympanum, the Bornean frog. This little guy is pretty unique. Along with only one other species of frog, it's among the only known amphibians to communicate with ultrasonic frequencies, and it appears to be the only frog that does so exclusively.
First of all, what IS ultrasonic? In reality, the term "ultrasonic" is a bit of a misnomer, or rather, it only applies to humans. The range of sound that humans can hear is between around 20Hz and 20kHz.
This is actually a pretty small range, many mammals can hear much higher frequencies, and animals which echolocate can hear up to 100kHz! So what's "ultrasonic" to us is barely interesting to a dog, let alone a bat.
Interestingly, while many mammals have finely tuned ears, most other vertebrates don't. Birds generally only hear up to 12kHz, and reptiles, amphibians, and fish are thought to be limited to 5kHz, which is a little bit higher than the highest note on a piano (4.1kHz).
Not only that, although many animals can HEAR in the ultrasonic, most don't communicate there. Bats are known to, as well as whales and some rodents. So a frog which could not only HEAR in the ultrasonic, but COMMUNICATE there, is a big event.
bornean frog2.jpg And here's the big event. The authors recorded the sounds of Bornean frogs, and got ultrasound in the waves. They then played the vocalizations BACK to another group of frogs, but carefully took OUT any normal range noise (they make chirps in the normal range too), to see if the frogs would respond to just ultrasonic sound. Sure enough, a call and response began, with the frogs chirping back at the ultrasonic signal, proving that the frogs can both hear and respond to ultrasonic sounds, and communicate in the ultrasonic range.
The researchers tested everything. They looked at the signals being passed in the auditory midbrain, as well as the vibrations of the frog's inner ear as it heard the sounds. They determined that, though the frogs could hear in a pretty good range, up to 40kHzm, and that they were most sensitive at ranges above human hearing, from 20-40kHz.
bornean frog3.jpg
So why is this a big deal? Well, it's the first time anything other than a mammal has been shown to hear AND communicate in the ultrasonic range. These guys are higher pitched than any other known frog. Ultrasonic does have limitations (doesn't carry very far through air), but is more energy efficient, and could help the frogs retain more energy for other things. And if they've got it, who knows how many other frogs could communicate ultrasonically, and we just weren't listening to the supersonic sounds?
Arch, V., Grafe, T., Gridi-Papp, M., & Narins, P. (2009). Pure Ultrasonic Communication in an Endemic Bornean Frog PLoS ONE, 4 (4) DOI: 10.1371/journal.pone.0005413

2 responses so far

  • JohnnieCanuck says:

    listening to the supersonic sounds

    I see what you did there. I'm almost certain it was irony and not error.
    Cool discovery.

  • Autodydactyl says:

    These findings could have implications with respect to current methods of surveying amphibians; typically organizations like Frogwatch encourage surveys based on calling activity. Data is gathered by individuals listening for calls. If frog calls can be made outside the human range of hearing, then data collected might be inaccurate. It may be necessary to do call surveys with recording devices that pick up ultrasound in order to identify species that call in a variety of ranges.

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