otherwise benefit if no one discovers them. However, like the other studies,
research on rhesus monkey food calls fails to address the long-term consequences of withholding information. For example, when silent peripheral
males are caught at a food source, how does their silence affect the odds of
joining a social group? If an estrous female finds a silent male at a food
source, is she less likely to initiate or accept a sexual consortship with him?
Are males less likely to withhold information about food in the presence of
an estrous female as opposed to a nonestrous female? Are males more likely
to remain quiet when no one is around or when an adult male is nearby?
One last example illustrates that lies of omission are possible outside the
contexts of food and alarm and provides suggestive evidence of more longterm costs and benefits of deception. Like many other primates (Hauser
1996), rhesus monkeys produce distinctive vocalizations during copulation
(Hauser 1993). These copulation screams are among the loudest calls in the
repertoire, are acoustically different from all other call types, and are highly
distinctive by individual. Thus, when a rhesus monkey gives a copulation
call, listeners know what the caller is doing and who he is. Focal animal
samples of 47 adult males and 59 estrous females during the mating season
indicated that males were more likely to call during copulation when the
number of estrous females was high than when it was low. Thus, males often
copulated in silence. Interestingly, silent males generally produced the facial
expressions that accompany the copulation call, suggesting that they can
inhibit the vocalization but not the facial gesture. When the data are divided
according to male dominance rank, high-ranking males called more often
than expected, low-ranking males called less often than expected, and
middle-ranking males called at the average rate.
To assess the consequences of calling as opposed to withholding information about mating behavior, we carried out analyses of the relationship
between mating success and call frequency. Results showed that for a given
female, the male who obtained the most copulations was a male who called
during copulation. Moreover, calling males copulated more overall than did
silent males. Thus, there may be a long-term cost to withholding information, at least in terms of behavioral measures of mating success. The benefits obtained from calling were, however, associated with costs. Analyses
revealed a statistically significant, positive relationship between the number
of copulation calls produced and the number of aggressive attacks received.
Withholding information about mating is therefore associated with lower
benefits than calling but is also associated with lower costs. It would seem
that the benefits of increased mating opportunities outweigh the costs of
intrasexual competition.
Thus, studies of rhesus copulation calls also satisfy the conditions for lies
of omission and provide suggestive evidence for punishment. Copulation
calls are strictly associated with the context of mating, and males often
produce such calls when they copulate. Given that males were more likely
to remain silent when competition for estrous females was high, and that
3. Unpacking “Honesty”
123
research on rhesus monkey food calls fails to address the long-term consequences of withholding information. For example, when silent peripheral
males are caught at a food source, how does their silence affect the odds of
joining a social group? If an estrous female finds a silent male at a food
source, is she less likely to initiate or accept a sexual consortship with him?
Are males less likely to withhold information about food in the presence of
an estrous female as opposed to a nonestrous female? Are males more likely
to remain quiet when no one is around or when an adult male is nearby?
One last example illustrates that lies of omission are possible outside the
contexts of food and alarm and provides suggestive evidence of more longterm costs and benefits of deception. Like many other primates (Hauser
1996), rhesus monkeys produce distinctive vocalizations during copulation
(Hauser 1993). These copulation screams are among the loudest calls in the
repertoire, are acoustically different from all other call types, and are highly
distinctive by individual. Thus, when a rhesus monkey gives a copulation
call, listeners know what the caller is doing and who he is. Focal animal
samples of 47 adult males and 59 estrous females during the mating season
indicated that males were more likely to call during copulation when the
number of estrous females was high than when it was low. Thus, males often
copulated in silence. Interestingly, silent males generally produced the facial
expressions that accompany the copulation call, suggesting that they can
inhibit the vocalization but not the facial gesture. When the data are divided
according to male dominance rank, high-ranking males called more often
than expected, low-ranking males called less often than expected, and
middle-ranking males called at the average rate.
To assess the consequences of calling as opposed to withholding information about mating behavior, we carried out analyses of the relationship
between mating success and call frequency. Results showed that for a given
female, the male who obtained the most copulations was a male who called
during copulation. Moreover, calling males copulated more overall than did
silent males. Thus, there may be a long-term cost to withholding information, at least in terms of behavioral measures of mating success. The benefits obtained from calling were, however, associated with costs. Analyses
revealed a statistically significant, positive relationship between the number
of copulation calls produced and the number of aggressive attacks received.
Withholding information about mating is therefore associated with lower
benefits than calling but is also associated with lower costs. It would seem
that the benefits of increased mating opportunities outweigh the costs of
intrasexual competition.
Thus, studies of rhesus copulation calls also satisfy the conditions for lies
of omission and provide suggestive evidence for punishment. Copulation
calls are strictly associated with the context of mating, and males often
produce such calls when they copulate. Given that males were more likely
to remain silent when competition for estrous females was high, and that
3. Unpacking “Honesty”
123