little attention to questions of honest or deceitful information transfer
(Hinde 1981). To the extent that information is transferred, it was often
implicitly assumed to be in both parties’ interests that the information be
accurate. However, the red deer example illustrates the weakness of this
assumption. What prevents every harem holder from roaring at very high
rates and thus repelling all comers without regard to his fighting ability?
Such a deceitful mutant would be spared the costs of fighting, and his genes
should spread rapidly through the population (Dawkins and Krebs 1978).
This in turn would generate strong selection for “skeptical” males who
ignored roaring altogether (Clutton-Brock and Albon 1979; Hinde 1981;
Krebs and Dawkins 1984). Thus, theory predicts that selection resulting
from receiver skepticism would eliminate the potential benefits of dishonest signaling. The only communication systems that would be stable in the
long run (an “evolutionarily stable strategy,” or ESS) are those in which
honesty is ensured by some mechanism. This search for such honest ESSs
in animal communication has been a major preoccupation of the field for
more than a decade.
The best-known mechanism by which honesty in communication could
be ensured was proposed by Zahavi (1975). Although initially repudiated
by many researchers (e.g., Maynard Smith 1976), Zahavi’s “handicap principle” received support from a mathematical model developed by Grafen
(1990) and has now become widely cited as a possible source of honesty in
communication. The handicap principle proposes that only heritable signals
that bear a high cost (the “handicap”), thereby reducing their bearer’s
fitness, can be stably honest. Of course, all signals bear some cost
(Bradbury and Vehrencamp 1998), so this statement alone has little
explanatory value. In Grafen’s (1990) analysis, a “handicap” signal of male
quality must be more expensive for low-quality males to perform than for
high-quality males. Although there has been growing agreement that Zahavian handicaps may play a role in the evolution of honest signaling, a more
recent paper by Siller (1998) exposes important flaws in the Grafen (1990)
model and again casts some doubt on the basic logic of the handicap principle. In particular, Siller (1998) demonstrates that there is no guarantee of
a single ESS under Grafen’s model conditions and opens up the possibility
of multiple coexisting ESSs. More generally, if there are mechanisms that
allow honest communication without a handicap, these less expensive alternatives should be favored over handicap signals, which can impose an arbitrarily high cost on their creators.
Again, the roaring of red deer illustrates the point. Harem-holding males
rarely feed during the rutting period and lose up to 20% of their body
weight. Toward the end of this exhausting period, male fighting ability drops
rapidly, with harem holders tending to tolerate rival males and lose fights
with males they had previously beaten.This decline occurs at different times
for different individuals but in each case is associated with a drastic reduction in roaring rates (Clutton-Brock and Albon 1979). This suggests that
66
W.T. Fitch and M.D. Hauser
(Hinde 1981). To the extent that information is transferred, it was often
implicitly assumed to be in both parties’ interests that the information be
accurate. However, the red deer example illustrates the weakness of this
assumption. What prevents every harem holder from roaring at very high
rates and thus repelling all comers without regard to his fighting ability?
Such a deceitful mutant would be spared the costs of fighting, and his genes
should spread rapidly through the population (Dawkins and Krebs 1978).
This in turn would generate strong selection for “skeptical” males who
ignored roaring altogether (Clutton-Brock and Albon 1979; Hinde 1981;
Krebs and Dawkins 1984). Thus, theory predicts that selection resulting
from receiver skepticism would eliminate the potential benefits of dishonest signaling. The only communication systems that would be stable in the
long run (an “evolutionarily stable strategy,” or ESS) are those in which
honesty is ensured by some mechanism. This search for such honest ESSs
in animal communication has been a major preoccupation of the field for
more than a decade.
The best-known mechanism by which honesty in communication could
be ensured was proposed by Zahavi (1975). Although initially repudiated
by many researchers (e.g., Maynard Smith 1976), Zahavi’s “handicap principle” received support from a mathematical model developed by Grafen
(1990) and has now become widely cited as a possible source of honesty in
communication. The handicap principle proposes that only heritable signals
that bear a high cost (the “handicap”), thereby reducing their bearer’s
fitness, can be stably honest. Of course, all signals bear some cost
(Bradbury and Vehrencamp 1998), so this statement alone has little
explanatory value. In Grafen’s (1990) analysis, a “handicap” signal of male
quality must be more expensive for low-quality males to perform than for
high-quality males. Although there has been growing agreement that Zahavian handicaps may play a role in the evolution of honest signaling, a more
recent paper by Siller (1998) exposes important flaws in the Grafen (1990)
model and again casts some doubt on the basic logic of the handicap principle. In particular, Siller (1998) demonstrates that there is no guarantee of
a single ESS under Grafen’s model conditions and opens up the possibility
of multiple coexisting ESSs. More generally, if there are mechanisms that
allow honest communication without a handicap, these less expensive alternatives should be favored over handicap signals, which can impose an arbitrarily high cost on their creators.
Again, the roaring of red deer illustrates the point. Harem-holding males
rarely feed during the rutting period and lose up to 20% of their body
weight. Toward the end of this exhausting period, male fighting ability drops
rapidly, with harem holders tending to tolerate rival males and lose fights
with males they had previously beaten.This decline occurs at different times
for different individuals but in each case is associated with a drastic reduction in roaring rates (Clutton-Brock and Albon 1979). This suggests that
66
W.T. Fitch and M.D. Hauser