Communication Theories - Soundscape Ecology: Principles, Patterns, Methods and Applications - page 99

In the communication process, the male-female song recognition seems an
important element influencing the way resources are shared within the pair, assur-
ing food and predatory avoidance.
The capacity to evaluate the distance at which a potential competitor is during a
precise moment is essential to save energy in territorial defense and in antipredatory
behavior. Ranging is defined as the ensemble of mechanisms that an individual
enacts to evaluate the distance to another individual. Several pieces of evidence
have confirmed the diffusion of this capacity among vocal animals, although
amplitude fluctuation, reverberation, blurring, attenuation, and signal-to-noise
ratio may reduce the efficiency of ranging procedure.
Among the communication strategies adopted by species the distress call repre-
sent a way to inform conspecifics and heterospecifics on the presence of a potential
predator. To be efficient these calls must warn other species about the menace and
at the same time to not inform predators about the location of the emitter.
Acoustic signals are used in several groups of species, humans included, to find
resources, to avoid predators, and to find or adapt locations for reproduction. In
other terms the acoustic cues are used in the orienting processing.
In the analysis of the complexity of the acoustic communication codes, the
acoustic codes specifically represent an interesting perspective of analysis. Codes
in biology are numerous and well documented. Every acoustic message is the result
of a sequence of elementary parts whose syntax represents a message. Acoustic
codes operate at intraspecific level but also at interspecific level, improving the
efficiency of communicative behavior. Code sequence may have a so robust
structure that despite the loss of a relevant part of the codes the message is not
degraded. An example of this aspect is represented by the acoustic structure of
blackcap song, where experimentally it has been verified that only when the
frequency modulation was suppressed or the number of syllables strongly reduced
was there a cessation of male reply to the playback.
Improving the efficacy of a signal is important to reduce the loss of energy and
on the other hand to optimize the information contained in the signal. The efficiency
of a signal largely depends on internal design and the capacity of an emitter to
separate the signal from the background noise.
A central principle in the communication theory states that biological signals are
honest: this means for an acoustic signal such as a song that the complexity of the
repertoire and all the secondary associated characters are expressions of natural
selection. Thus, the theory of honest signals becomes a cornerstone in the ecology
of acoustic communication. There are several types of evidence that confirm this
hypothesis for many animals.
Dialects, which are local variations of acoustic performance, are an important
aspect of adaptation to local conditions and represent the initial stages of future
acoustic divergence.
To reduce interspecific competition, birds and frogs can use acoustic partitioning
that consists of changing the time at which to start an acoustic performance in the
presence of other concurrent singers. This process allows species to share the same
sonic context, reducing the risk of interspecific masking or having equivocal
acoustic signals.