Making noise in a noisy environment

A friend sends news of the dilemma that the USAF F 22's flying over Baghdad have their electronic sensors swamped by the electronic smog generated by the city (1.29.07 Aviation Week & Space Technology) - which reminds me of a clever group of frogs faced with a similiar problem. Here is the worrying bit - they are Chinese frogs.

Torrent frogs have adapted to living in the sound rich environment of waterfalls and splashing water. They have no apparent eardrums, - the reason is that (Nature March 16th 2006 (subscription - BBC ) they have very thin, delicate eardrums and connecting bones deep in their skull to detect ultrasound. Recessed ears shorten the path between eardrums and the ear, enabling the transmission of ultrasound to the ears.

Kraig Adler, a bilogist from Cornell University was surveying Chinese amphibians and told Albert S. Feng, a professor of molecular and integrative physiology at the University of Illinois at Urbana-Champaign of these strange singing frogs.

Feng and colleagues have now conducted field studies of male Amolops tormotus that inhabits Huangshan Hot Springs, Anhui Province a popular scenic mountainous area, full of noisy waterfalls and wildlife west of Shanghai.

The human ear can experience sound up to 20 kilohertz and the frogs could generate sound up to 28 kilohertz. Under observation and prompted by generated ultrasonic burts it was evident that the frogs were responding and communicating. Analysis of 12 hours of tapes of audible calls from 21 males found no two calls to be identical either between animals or within an individual's repertoire. Also, the recordings chronicle the first known ultrasonic noises from frogs.

“Nature has a way of evolving mechanisms to facilitate communication in very adverse situations,” Feng said. “One of the ways is to shift the frequencies beyond the spectrum of the background noise. Mammals such as bats, whales and dolphins do this, and use ultrasound for their sonar system and communication. Frogs were never taken into consideration for being able to do this.” ... simply no-one had ever bothered to look before.

Apparently, according to Professor Tim Halliday of the Department of Biological Sciences at The Open University, UK, some frogs in similiar noisy sites have solved communication another way

"At least two other frog species, one from Borneo, the other from South America, rather than calling to attract females and deter rival males, they use visual displays, waving their brightly coloured feet." Borneo tree hole frogs - less than 1 inch long (Nat Geog.) like Metaphrynella sundana tune their calls to be amplified by the megaphone like hollows they live in to carry further and louder. Male frogs increased the volume of mating calls by 10 to 15 decibels by leveraging the resonant frequency of their hole.

Bloody men - always trying to attract attention.