1. Introduction
When autumn arrives in northern Europe, female red deer (Cervus elaphus
L.) begin to congregate. The mating season has begun. They are soon joined
by males, who have spent the previous ten months in preparation, feeding
and sparring. Some of the males herd females into groups, or “harems,”
which they vigorously defend against other males. A prominent component
of this defense is roaring, a powerful, low-pitched groaning sound made
only by males and primarily by harem holders. Why do males produce these
sounds, and what effect do they have on listeners? Early observers (Darling
1937) suggested that the roars intimidated rivals and repelled intruders
without the need for a dangerous fight. However, selection should favor
opponents who are not so easily intimidated and base their behavior solely
on a balanced assessment of their chances of winning a fight and inheriting
the herd (Maynard Smith and Price 1973). In a classic paper, Clutton-Brock
and Albon (1979) showed that roaring provides a source of information relevant to this decision: roaring rates of individual males are highly correlated with their fighting ability and thus provide an accurate indication of
the males’ ability to repel intruders. They also demonstrated, in a series of
playback experiments, that rival males attend to this information, responding preferentially to high roar rates and ignoring the roars of young, small
males. Red deer roaring has since become a classic example of “truth in
advertising” in an animal vocalization.
“Honest signaling” in animal communication refers to signals that
provide accurate information to perceivers either about the quality or properties of the signaler itself (e.g., advertisement calls) or about something in
the environment (e.g., alarm calls). The degree to which animal signals are
honest in this sense has been a perennially provocative problem and has
generated significant theoretical advances, along with some empirical work,
in the last few decades. Early workers in ethology were primarily interested
in the historical evolutionary origins of particular communicative displays
(e.g., via “ritualization” of intention movements; Cullen 1966) and devoted
65
3
Unpacking “Honesty”: Vertebrate
Vocal Production and the Evolution
of Acoustic Signals
W. Tecumseh Fitch and Marc D. Hauser
When autumn arrives in northern Europe, female red deer (Cervus elaphus
L.) begin to congregate. The mating season has begun. They are soon joined
by males, who have spent the previous ten months in preparation, feeding
and sparring. Some of the males herd females into groups, or “harems,”
which they vigorously defend against other males. A prominent component
of this defense is roaring, a powerful, low-pitched groaning sound made
only by males and primarily by harem holders. Why do males produce these
sounds, and what effect do they have on listeners? Early observers (Darling
1937) suggested that the roars intimidated rivals and repelled intruders
without the need for a dangerous fight. However, selection should favor
opponents who are not so easily intimidated and base their behavior solely
on a balanced assessment of their chances of winning a fight and inheriting
the herd (Maynard Smith and Price 1973). In a classic paper, Clutton-Brock
and Albon (1979) showed that roaring provides a source of information relevant to this decision: roaring rates of individual males are highly correlated with their fighting ability and thus provide an accurate indication of
the males’ ability to repel intruders. They also demonstrated, in a series of
playback experiments, that rival males attend to this information, responding preferentially to high roar rates and ignoring the roars of young, small
males. Red deer roaring has since become a classic example of “truth in
advertising” in an animal vocalization.
“Honest signaling” in animal communication refers to signals that
provide accurate information to perceivers either about the quality or properties of the signaler itself (e.g., advertisement calls) or about something in
the environment (e.g., alarm calls). The degree to which animal signals are
honest in this sense has been a perennially provocative problem and has
generated significant theoretical advances, along with some empirical work,
in the last few decades. Early workers in ethology were primarily interested
in the historical evolutionary origins of particular communicative displays
(e.g., via “ritualization” of intention movements; Cullen 1966) and devoted
65
3
Unpacking “Honesty”: Vertebrate
Vocal Production and the Evolution
of Acoustic Signals
W. Tecumseh Fitch and Marc D. Hauser