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...e provides new evidence for vocal behavioural plasticity, and further reveals how behavioural plasticity together with evolutionary adaptations can minimize the detrimental effects of ambient noise on communication. 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.Animal communication signals enroute from sender to receiver are often subject to interference. For example, loud ambient noise for acoustic signals, or murky media for visual signals, can reduce the ability of receivers to detect those signals, a phenomenon known as ‘masking’ (Klump 1996). Signals that minimize masking in their respective habitats have generally been favoured over evolutionary time because of their greater efficacy (Ryan & Cummings 2005). In the acoustic realm, signal frequency and timing features evolve to minimize habitat-specific degradation (acoustic adaptation hypothesis; Morton 1975; Wiley 1991). Masking interference from other vocalizing animals provides another source of selection on vocal behaviour. In chorus settings, taxa as diverse as frogs, cicadas and birds reduce masking interference by partitioning their signals in time and structure among spec...

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... on previous discussions of signal evolution by Wiley (1983, 1994, 2000a) suggesting that choosy females should favor the evolution of male signals that are highly stereotyped and redundant. These predictions are based on signal detection theory, as it applies to intersexual communication during mate choice. 2. Mate choice as a signal detection problem In the study of animal communication, signal detection theory is most often applied to communication in noisy environments, such as in situations where signals degrade during transmission (Wiley & Richards, 1982) or are masked by other stimuli (Klump, 1996; Wollerman & Wiley, 2002; Slabbekoorn, 2004; Luther & Wiley, 2009). All forms of communication occur in the presence of some form of background noise (Wiley, 2006). However, this model can also be applied effectively to communication during mate choice, as the difficulties faced by male signalers are largely the same (Wiley, 1994, 2000a). In both cases, there is a less than certain probability that a receiver will respond favorably to a male’s signal, in the former case because of environmental interference and in the latter case because of a female’s fastidiousness in choosing a mate. For di...

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...n the boxplot illustrating the effect of group composition on social vocalization levels (Fig. 3), the data suggests that humpback whale singletons, not involved in social interactions, vocalized at higher levels compared to other group compositions. This is clear in the 0 to 2000 m distance bin where we assume the effect of the distance bias is minimal. The source level of a vocal signal is a crucial parameter determining the active space for communication; higher level signals travel further and can be better detected by the receiver against the background of interfering sounds (reviewed in Klump, 1996). Killer whales have been found to switch from “longdistance” more intense vocal signals to “short-distance” less intense signals depending on the behavioral context (Miller, 2006). Similarly, lone humpback whales (singletons) may be using long-distance more intense vocalizations to signal (or broadcast) to other groups or whales in the area (inter-group signaling), while whales within a group could be using more short-distance less intense signals directed at other members within the group (intra-group signaling) or nearby groups. Interestingly, the minimum source level of vocalizations recor...

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...and to discriminate those sounds from behaviorally relevant sounds [32], [73], [74]. Spectral and temporal correlations within and between noise sources can further enhance signal detectability [71], =-=[75]-=-, [76]. Individual singers are localizable by other whales [37], [43], [77], and produce songs asynchronously [10], [78]. Thus, potentially interfering songs constitute acoustically and spatially sepa...

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...hick, which can detect at the same distance (7 m) a parental call 6 dB below the noise of the colony (Aubin & Jouventin 1998). Such detection levels have been found in some other species (reviewed in =-=Klump 1996-=-), but they were obtained in laboratory conditions using operant conditioning techniques with pure-tone signals masked with a continuous broad-band noise. Parameters Encoding Acoustic Identity The Adé...

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...8; Owings & Morton 1998). In temperate latitudes, the diversity of taxa is more restricted and sources of abiotic noise, like wind, rain and running water are likely to have a higher importance (e.g. =-=Klump 1996-=-). Vertebrates have developed strategies to overcome noise interference, thus facilitating the transmission of acoustic signals to potential receivers. Various vertebrates, including humans, increase ...

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... whysI found an effect for call duration, but not repetition rate. Noise in naturalsenvironments is rarely continuous and signallers can adapt by calling during gaps insthe temporal pattern of noise (=-=Klump 1996-=-). Smith and Bain (2002) found thatsbetween 1999 and 2001 boats accompanied whales for up to 10 hours a day, 7 days asweek and whales were not accompanied by boats in only 9% of encounters suggestings...

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...raints? Detection of signals in noise is a complex issue. The most detailed knowledge of the mechanisms involved comes from psychoacoustic experiments performed in controlled laboratory environments (=-=Klump 1996-=-). Few field studies have studied experimentally how signals of animals are detected amidst background noise in the natural environment. The capacity of the king penguin chick to recognize the parenta...

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...raints? Detection of signals in noise is a complex issue. The most detailed knowledge of the mechanisms involved comes from psychoacoustic experiments performed in controlled laboratory environments (=-=Klump 1996-=-). Few field studies have studied experimentally how signals of animals are detected amidst background noise in the natural environment. The capacity of the king penguin chick to recognize the parenta...

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...72/01/000000 + 00$35.00/0 2001 The Association for the Study of Animal Behaviour1 (Ehret & Gerhardt 1980; Bailey & Morris 1986; Gerhardt & Klump 1988; Brush & Narins 1989; Schwartz & Gerhardt 1989; =-=Klump 1996-=-; Wollerman 1999). The effect of background sound is particularly striking on females’ ability to detect any one individual male’s calls. Because of the difficulties of detection, a female can detect ...