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Frogs Communicate with Ultrasound

March 16, 2006

A Chinese frog has made a successful pitch to join an exclusive club—it’s the latest addition to the range of animals known to communicate by ultrasound. Membership of the group had previously included only bats, marine mammals and some rodents.

Joining them now is the concave-eared torrent frog (Amolops tormotus). The creature’s croak contains both audible and ultrasonic components, which allow their calls to be heard against the babbling background of the streams where they live.

Albert Feng and colleagues recorded the croaks, split them into their constituent frequencies, and tested other frogs’ responses to them. They found that males produce answering croaks in response to both the audible and the ultrasonic components of the calls. Furthermore, acoustic playback experiments in the frogs’ natural habitat and electrophysiological brain recordings confirmed the ultrasonic hearing capacity of Amolops tormotus and of a related species facing similar environmental constraints.

As they report in the 03 16 06 Nature, this is the first example of such a tactic from outside the mammalian class, meaning that the trick has evolved more than once in different animal groups.

Abstract © 2006 Nature (slightly modified)

“Ultrasonic communication in frogs,” Albert S. Feng, Peter M. Narins, Chun-He Xu, Wen-Yu Lin, Zu-Lin Yu, Qiang Qiu, Zhi-Min Xu, Jun-Xian Shen, Nature, March 16, 2006

Albert Feng, University of Illinois, Urbana

Below: a two-note call of Amolops tormotus.
Sound spectrogram (top panel), waveform (bottom panel), and instantaneous amplitude spectra (inset, taken at the point indicated by the arrow-head).

The background noise up to 20 kHz is due to the rushing water in the Tau Hua Creek, Anhui Province, China.

Amalops Spectrogram

Part a, Figure 1, “Old World frog and bird vocalizations contain prominent ultrasonic harmonics,” Peter M. Narins, Albert S. Feng, Wenyu Lin, Hans-Ulrich Schnitzler, Annette Denzinger, Roderick A. Suthers, Chunhe Xu,
J. Acoust. Soc. Am. 115 (2), February 2004