both high- and low-ranking males have the capacity to remain silent during
copulation, these data indicate the ability to withhold information about
mating. Although such lies of omission are associated with reduced aggression, they are also associated with increased costs due to the fact that silent
males obtain fewer opportunities to mate than do vocal males. It would be
interesting to follow up this work with studies in captivity that explore more
carefully the mechanisms underlying mating decisions and whether females
copy the mating preferences of others. Thus, one could set up a situation in
which one female watched a male copulate and vocalize with female A and
a second male copulate and remain silent with female B. Given a choice,
which male will the observer female select? On Cayo Santiago, some
females cycle in and out of estrous several times during the mating season.
Sometimes females mate with the same male on each cycle, and sometimes
they mate with different males. When females switch males, it would be
interesting to determine whether they switched from a silent to a vocal
male. Such studies would help our understanding of why rhesus monkeys
sometimes choose to vocalize when they mate and sometimes choose to
remain silent.
4. Summary and Conclusions
In this paper, we have argued that the study of the proximate mechanisms
underlying vocal behavior, both physiological and cognitive, is a necessary
part of the study of the evolution of communication and in particular for
analyzing honesty in communication. In the first section, we surveyed basic
principles of vocal production in terrestrial vertebrates and the morphological diversity of their production systems. We then provided some examples of the interactions between acoustics and anatomy that can enforce
honesty or subvert it. In the second section, we examined the evidence for
cognitive mechanisms that allow animals to produce deceptive calls as well
as “retaliatory” perceptual mechanisms that allow perceivers to accurately
identify and ignore (and in some cases even punish) the deceivers. Both
vocal-production mechanisms and cognitive mechanisms controlling vocalization play a crucial role in determining what is possible or impossible in
a particular species’ communication system. A better understanding of
these mechanisms can lead to rich insights into the evolution of acoustic
communication.
For the reader already interested in mechanism, the chapter also provided
illustrations of the value of an ultimate evolutionary viewpoint. An evolutionary perspective proves valuable both for identifying functional problems that are solved by communicators and for using phylogenies and the
comparative method as tools to identify and understand widespread selective pressures and functional constraints. The species we observe today are
the outcome of a long, dynamic process of coevolution and interaction.
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W.T. Fitch and M.D. Hauser
copulation, these data indicate the ability to withhold information about
mating. Although such lies of omission are associated with reduced aggression, they are also associated with increased costs due to the fact that silent
males obtain fewer opportunities to mate than do vocal males. It would be
interesting to follow up this work with studies in captivity that explore more
carefully the mechanisms underlying mating decisions and whether females
copy the mating preferences of others. Thus, one could set up a situation in
which one female watched a male copulate and vocalize with female A and
a second male copulate and remain silent with female B. Given a choice,
which male will the observer female select? On Cayo Santiago, some
females cycle in and out of estrous several times during the mating season.
Sometimes females mate with the same male on each cycle, and sometimes
they mate with different males. When females switch males, it would be
interesting to determine whether they switched from a silent to a vocal
male. Such studies would help our understanding of why rhesus monkeys
sometimes choose to vocalize when they mate and sometimes choose to
remain silent.
4. Summary and Conclusions
In this paper, we have argued that the study of the proximate mechanisms
underlying vocal behavior, both physiological and cognitive, is a necessary
part of the study of the evolution of communication and in particular for
analyzing honesty in communication. In the first section, we surveyed basic
principles of vocal production in terrestrial vertebrates and the morphological diversity of their production systems. We then provided some examples of the interactions between acoustics and anatomy that can enforce
honesty or subvert it. In the second section, we examined the evidence for
cognitive mechanisms that allow animals to produce deceptive calls as well
as “retaliatory” perceptual mechanisms that allow perceivers to accurately
identify and ignore (and in some cases even punish) the deceivers. Both
vocal-production mechanisms and cognitive mechanisms controlling vocalization play a crucial role in determining what is possible or impossible in
a particular species’ communication system. A better understanding of
these mechanisms can lead to rich insights into the evolution of acoustic
communication.
For the reader already interested in mechanism, the chapter also provided
illustrations of the value of an ultimate evolutionary viewpoint. An evolutionary perspective proves valuable both for identifying functional problems that are solved by communicators and for using phylogenies and the
comparative method as tools to identify and understand widespread selective pressures and functional constraints. The species we observe today are
the outcome of a long, dynamic process of coevolution and interaction.
124
W.T. Fitch and M.D. Hauser