Selfish or altruistic? An analysis of alarm call function in wild capuchin monkeys, Cebus apella nigritus

Abstract

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Production and perception of situationally variable alarm calls in wild tufted capuchin monkeys (Cebus apella nigritus)

“…First, the 220 initial calls given should be the most likely to reflect the callerÕs perceived risk (see Blumstein & 221 Armitage 1997). Second, because alarm calling among tufted capuchins tends to attract 222 conspecific mobbers (Wheeler 2008) who often begin to call once they have detected the 223 predator model, calls given after this initial period could not always be easily assigned to a 224 particular individual. Only those call bouts that did not overlap with calls from other group 225 members and which were of sufficiently high quality (e.g., with low background noise) were 226 used to determine how many calls were given over the first 10 seconds.…”

“…The types of calls given to raptor models were recorded on 13 occasions, to ocelot models on 35 336 occasions, and to snake models on 34 occasions (see Wheeler 2008 for discussion of detections 337 which did not result in a vocal response). When considering only one reaction per individual, the 338 call type or series produced in response to a model was better explained by stimulus category 339 (i.e., raptor, felid, or snake; multinomial logistic regression: N=32, χ 2 =35.51, df=6, p<0.0001) 340 than by risk-urgency (same logistic regression: χ 2 =2.54, df=6, p=0.863; Fig.…”

“…To test whether responses to the calls are stimulus independent, playbacks of 122 the call types elicited by the predator models were conducted. these snakes certainly pose a mortal threat to capuchins that approach too closely, the monkeys 146 are likely too large to be preyed upon by these species (see Wheeler 2008). 147…”

Monkeys crying wolf? Tufted capuchin monkeys use anti-predator calls to usurp resources from conspecifics

“…A Fisher's exact test was used to test whether subordinate individuals were more likely to produce RRDAs than dominants. The six highest ranking individuals (as determined through analysis of dyadic agonistic interactions; see Wheeler 2008 for additional details), including the group's four adult males and the two highest ranking adult females, were placed in the 'dominant' category as these are the only individuals who were able to effectively exclude more subordinate individuals (18 of which were sampled) from accessing the platforms (personal observation). For this test, each individual was scored on the basis of whether it was observed to give an RRDA at least once during any of the first 20 experiments in which it was a focal animal.…”

“…Anti-predator signals have long been challenging to explain because of the danger that the signaller imparts on itself in an apparent attempt to warn others of impending danger. While numerous hypotheses potentially explain how an individual who has detected a predator can benefit directly or indirectly by eliciting antipredator behaviour in conspecifics (see the reviews by Hauser 1996;Wheeler 2008), individuals could also use alarm calls in the absence of a predator to distract signal receivers and take advantage of the momentary diversion of attention. Cases such as this wherein individuals produce a signal outside its 'normal' context in order to distract listeners is a form of what has been termed tactical or functional deception (Whiten & Byrne 1988;Hauser 1996Hauser , 1997.…”