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The energetics of singing in noise - metabolic and respiratory costs of increasing song amplitude [abstract]

Zollinger, S A, Goller, F & Brumm, H (2012). The energetics of singing in noise - metabolic and respiratory costs of increasing song amplitude [abstract]. Bioacoustics, Volume 21 (1): 85



In an increasingly noisy world, animals that rely on acoustic communication are faced with additional challenges in trying to make their signals heard. One response to a rise in background noise is to make your signal louder. However, increasing vocal amplitude to higher and higher levels may incur costs and is likely subject to physiological or anatomic constraints. Previous studies in three different songbird species suggest that the metabolic cost of song is fairly small relative to resting metabolic rate (requiring an 1.7 – 3.4 - fold increase). Another study found that when subsyringeal air sac pressure was experimentally reduced, song amplitude decreased. This suggests that singing louder may require greater subsyringeal pressure, and potentially greater respiratory muscle activity and/or greater volume of air than that needed to produce a quieter signal of equal duration. Here we examine the potential costs of increasing song amplitude in zebra finches (Taeniopygia guttata) singing in environments with different background noise levels. For each 4 dB increase in background noise amplitude, birds significantly increased their song amplitude. To test whether these amplitude increases required associated increases in metabolic energy or subglottal air sac pressure, we measured oxygen consumption, subsyringeal air sac pressure and song bout duration. We recorded oxygen consumption by training birds to sing while wearing small, lightweight respirometry helmets. Preliminary results suggest that oxygen consumption per motif may increase with increasing amplitude, but within-bird variability for metabolic rate, respiratory patterns and song duration in different noise conditions was high.