Md. Hauser et P. Marler, FOOD-ASSOCIATED CALLS IN RHESUS MACAQUES (MACACA-MULATTA) .2. COSTS AND BENEFITS OF CALL PRODUCTION AND SUPPRESSION, Behavioral ecology, 4(3), 1993, pp. 206-212
In field experiments, free-ranging rhesus macaques (Macaca mulatta) ga
ve food-associated calls in 45% of the trials in which they were prese
nted with food, either monkey chow or coconut; they did not call in co
ntrol trials when sticks were presented. Consistent with prior natural
istic observations, adult females called in a higher proportion of tri
als than adult males. Coconut, one of the most highly preferred food i
tems in the diet, elicited different call types and a higher rate of c
alling from ''discoverers'' than did chow. The call types produced to
coconut (warbles, harmonic arches, and chirps) were primarily those th
at, under nonexperimental conditions, were associated with relatively
rare and preferred foods. In contrast, coos and grunts were primarily
produced in response to chow. The relative hunger level of the discove
rer had no significant effect on the call type produced but did affect
the rate of call production; discoverers called at higher rates when
they were hungry. Upon hearing food-associated calls, individuals with
in the vicinity of the discovery responded by rapidly approaching the
caller. A larger number of individuals approached when discoverers cal
led than when they did not. Discoverers who failed to call received si
gnificantly more aggression from group members and, in the case of fem
ales, actually consumed less food than discoverers who called. The pro
bability of receiving aggression did not appear to be associated with
the discoverer's dominance rank. Results suggest that food-associated
calls are ''honest'' signals reflecting food possession. Those who fai
l to signal and are caught with food are apparently punished.