Hot topics in animal bioacoustics

Abstract

Discoveries in the amphibian flipper of the animal bioacoustics community include Alejandro Purgue’s discovery that North American Bullfrogs emit 90% of the power of their calls from their eardrums, and only 10% from their vocal sacs has perhaps been the most original and surprising result of this decade. Peter Narins, Ted Lewis, and Blinda McClelland have shown that males of the endemic Madagascar tree frog have hyperextended their vocal repertoire to least 28 different calls. From the bat wing, von Helversen and von Helversen report that a bat-pollinated vine directs echolocating pollinators to its flowers by means of an acoustic guide. Valentine and Moss report on specializations in the bat superior colliculus for acoustic orientation by sonar. Three groups have new findings regarding temporary threshold shift (TTS) in marine mammals. Schusterman and Kastak observed a very small shift after broadband noise of over 20-min duration in a sea lion. Au and Nachtigall observed a 12-dB shift using one-octave noise of 179 dB, that is, 1 μPa in a bottlenose dolphin. Carder, Finneran, Ridgway, Schlundt and co-workers have produced TTS of 6 to 18 dB using 1-s tones of 192 to 202 dB in white whales and dolphins.