Selective encoding of conspecific signals in a noisy habitat
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1
Karl-Franzens University Graz, Zoology, Austria
In a habitat with multiple sound-producing species, such like the nocturnal tropical rainforest, conspecific signals sometimes overlap in the time and frequency domain with heterospecific signals, which challenges the detection of relevant signals and their discrimination from irrelevant noise by receivers.
We studied this problem in two tropical katydid species of the genus Mecopoda where males of one species produce chirps in regular intervals of 2 s (species “S” named after Sismondo 1990), whereas the other produces long-lasting continuous trills with a rather similar frequency spectrum (3-95 kHz). We investigated the neuronal basis of detecting conspecific signals in the chirping species during simultaneous playbacks of either natural nocturnal habitat noise or varying levels of the calling song of the trilling species.
We monitored the activity of TN-1, an afferent auditory interneuron known for its reliable chirp responses from previous studies [1]. Conspecific chirps are reliably represented as bursts of AP´s in this neuron even at a signal-to-noise-ratio of 0 dB (background noise or the trilling song broadcast at the same amplitude as the chirp, 65 dB SPL). Although TN-1 responses gradually declined with increasing levels of the song of the trilling species, TN-1 still discharged with 2 APs/chirp at a S/N ratio of -5 dB. Interestingly, rainforest background noise or the song of the trilling species alone hardly ever elicited a response, except after stimulus onset. Modifying either the frequency content of the chirp or the species-specific temporal pattern in the amplitude modulation of the syllable sequence within the chirp resulted in a reduced TN-1 response during simultaneous playback of the trilling song. Therefore, the selective response of TN-1 to conspecific signals appears to depend on differences in temporal structure and frequency content of conspecific signals and natural maskers.
Acknowledgements
Research was funded by the Austrian Science Fund (FWF): P21808-B09.
References
[1] Siegert, M. E., Römer, H., Hashim, R. and Hartbauer, M. (2011) Neuronal correlates of a preference for leading signals in the synchronizing bushcricket Mecopoda elongata (Orthoptera, Tettigoniidae). Journal of the Experimental Biology, 214:3924–3934.
Keywords:
acoustic communication,
bushcricket,
habituation,
Noise,
Signal detection,
TN-1
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Poster Presentation (see alternatives below as well)
Topic:
Sensory: Audition
Citation:
Hartbauer
M,
Siegert
ME and
Römer
H
(2012). Selective encoding of conspecific signals in a noisy habitat.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00095
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Received:
20 Apr 2012;
Published Online:
07 Jul 2012.
*
Correspondence:
Dr. Manfred Hartbauer, Karl-Franzens University Graz, Zoology, Graz, Styria, 8010, Austria, manfred.hartbauer@uni-graz.at