@article {52528,
	title = {Eavesdropping avoidance and sound propagation: the acoustic structure of soft song},
	journal = {Animal Behaviour},
	volume = {134},
	year = {2017},
	month = {Jan-12-2017},
	pages = {113 - 121},
	abstract = {Many species use low-amplitude (soft) song during close range interactions with conspecifics, such as in aggressive encounters or courtship displays. It has been suggested that soft song is adapted to limit eavesdropping by conspecifics or predators through reduced signal transmission range. If so, other structural features of soft song, besides amplitude, should be adapted to reduce transmission. The soft songs of white-throated thrushes, Turdus assimilis, have properties expected to lower transmission, such as higher frequency and broader bandwidth relative to broadcast songs. We compared the transmission properties of broadcast and soft syllables using a sound propagation field experiment. When played at the same amplitude as broadcast song, soft song showed greater excess attenuation and blur ratios and lower signal-to-noise ratios. Lowering the frequency of soft syllables recovered similar transmission properties as those of broadcast syllables. Further analysis of spectral traits showed that excess attenuation values were mainly affected by minimum frequency and peak frequency, while blur ratio variation was predominantly affected by bandwidth, and signal-to-noise ratios were predicted by bandwidth and peak frequency. Additionally, soft song had more frequency overlap with background noise than broadcast song. These results support the eavesdropping hypothesis: aspects of the acoustic structure of soft signals in addition to low amplitude seem to have been shaped by selection to reduce transmission and avoid eavesdroppers.},
	keywords = {communication range, signal design, song mode, sound degradation, sound transmission, Turdus, whispered communication},
	issn = {00033472},
	doi = {10.1016/j.anbehav.2017.10.008},
	url = {http://linkinghub.elsevier.com/retrieve/pii/S0003347217303329},
	author = {Vargas-Castro, Luis E. and Sandoval, Luis and Searcy, William A.}
}
@article {50498,
	title = {To seek or speak? Dual function of an acoustic signal limits its versatility in communication},
	journal = {Animal Behaviour},
	volume = {127},
	year = {2017},
	month = {Jan-05-2017},
	pages = {135 - 152},
	abstract = {<p>The perception of different attributes of conspecifics is an integral part of intraspecific communication. It can facilitate the recognition of interaction partners or the assessment of potential mates. Acoustic signals can encode fine-scaled information through the interplay of acoustic variability and specificity. A reliable vocal signature is both unique within a class and variable between classes. Therefore, acoustic complexity might be associated with the number of classes to be discriminated. We investigated the assumption that limitations to signal design may affect the communicative functionality of a signal. To do so, we chose a signal with potentially dual functionality which may therefore display such limitations. In bats, echolocation is used primarily for foraging and orientation but there is increasing support for its additional role in communication. An acoustic analysis of echolocation pulses of the bat Rhinolophus clivosus confirmed sex and individual vocal signatures in echolocation pulses. A habituation\&ndash;dishabituation playback experiment suggested that bats perceived these signatures because listening bats clearly discriminated between the sexes (two classes) and between individuals (representatives of a multiclass category), although to different degrees. The simple acoustic structure of these vocalizations provides sufficient specificity for sex discrimination but has limitations for individual discrimination because pulse parameters of individuals increasingly overlapped with increasing group size. We conclude that selection for the primary function of echolocation restricts the acoustic space available for communication. However, we frequently observed echolocation pulses with conspicuous structural modifications. Statistical analyses revealed that these vocalizations yielded increased individual distinctiveness. Such added systematic variation may indicate a communicative function and perhaps a signalling intent of the emitter, although the latter has yet to be tested. The findings suggest that the required specificity for effective communication could be obtained through modification of echolocation variants when adaptations for orientation and foraging constrain the evolution of complex communication signatures.</p>
},
	keywords = {acoustic communication, bats, co-option, constraints, eavesdropping, echolocation, habituation{\textendash}dishabituation playback, individual and sex discrimination, signal design, vocal signatures},
	issn = {00033472},
	doi = {10.1016/j.anbehav.2017.03.005},
	url = {http://linkinghub.elsevier.com/retrieve/pii/S0003347217300775},
	author = {Anna Bastian and David Steve Jacobs}
}
@article {47320,
	title = {To seek or speak? Dual function of an acoustic signal limits its versatility in communication},
	journal = {Animal Behaviour},
	volume = {127},
	year = {2017},
	month = {Jan-05-2017},
	pages = {135 - 152},
	abstract = {<p>The perception of different attributes of conspecifics is an integral part of intraspecific communication. It can facilitate the recognition of interaction partners or the assessment of potential mates. Acoustic signals can encode fine-scaled information through the interplay of acoustic variability and specificity. A reliable vocal signature is both unique within a class and variable between classes. Therefore, acoustic complexity might be associated with the number of classes to be discriminated. We investigated the assumption that limitations to signal design may affect the communicative functionality of a signal. To do so, we chose a signal with potentially dual functionality which may therefore display such limitations. In bats, echolocation is used primarily for foraging and orientation but there is increasing support for its additional role in communication. An acoustic analysis of echolocation pulses of the bat Rhinolophus clivosus confirmed sex and individual vocal signatures in echolocation pulses. A habituation\&ndash;dishabituation playback experiment suggested that bats perceived these signatures because listening bats clearly discriminated between the sexes (two classes) and between individuals (representatives of a multiclass category), although to different degrees. The simple acoustic structure of these vocalizations provides sufficient specificity for sex discrimination but has limitations for individual discrimination because pulse parameters of individuals increasingly overlapped with increasing group size. We conclude that selection for the primary function of echolocation restricts the acoustic space available for communication. However, we frequently observed echolocation pulses with conspicuous structural modifications. Statistical analyses revealed that these vocalizations yielded increased individual distinctiveness. Such added systematic variation may indicate a communicative function and perhaps a signalling intent of the emitter, although the latter has yet to be tested. The findings suggest that the required specificity for effective communication could be obtained through modification of echolocation variants when adaptations for orientation and foraging constrain the evolution of complex communication signatures.</p>
},
	keywords = {acoustic communication, bats, co-option, constraints, eavesdropping, echolocation, habituation{\textendash}dishabituation playback, individual and sex discrimination, signal design, vocal signatures},
	issn = {00033472},
	doi = {10.1016/j.anbehav.2017.03.005},
	url = {http://linkinghub.elsevier.com/retrieve/pii/S0003347217300775},
	author = {Anna Bastian and David Steve Jacobs}
}
