Should I stay or should I go? Initiation of joint travel in mother–infant dyads of two chimpanzee communities in the wild

Abstract

It is well established that great apes communicate via intentionally produced, elaborate and flexible gestural means. Yet relatively little is known about the most fundamental steps into this communicative endeavour—communicative exchanges of mother–infant dyads and gestural acquisition; perhaps because the majority of studies concerned captive groups and single communities in the wild only. Here, we report the first systematic, quantitative comparison of communicative interactions of mother–infant dyads in two communities of wild chimpanzees by focusing on a single communicative function: initiation of carries for joint travel. Over 156 days of observation, we recorded 442 actions, 599 cases of intentional gesture production, 51 multi-modal combinations and 80 vocalisations in the Kanyawara community, Kibale National Park, Uganda, and the Taï South community, Taï National Park, Côte d’Ivoire. Our results showed that (1) mothers and infants differed concerning the signal frequency and modality employed to initiate joint travel, (2) concordance rates of mothers’ gestural production were relatively low within but also between communities, (3) infant communicative development is characterised by a shift from mainly vocal to gestural means, and (4) chimpanzee mothers adjusted their signals to the communicative level of their infants. Since neither genetic channelling nor ontogenetic ritualization explains our results satisfactorily, we propose a revised theory of gestural acquisition, social negotiation, in which gestures are the output of social shaping, shared understanding and mutual construction in real time by both interactants.Electronic supplementary materialThe online version of this article (doi:10.1007/s10071-015-0948-z) contains supplementary material, which is available to authorized users.

Play-solicitation gestures in chimpanzees in the wild: flexible adjustment to social circumstances and individual matrices

“…It is, however, not clear whether the hand-clasp qualifies as gesture, since its communicative function is still debated [82] and it might simply act as a stabilizing tool. Our findings provide further support for the social negotiation hypothesis proposed by Fröhlich et al [36] which postulates that gestures originate from the exchange of social behaviours resulting in a mutual recognition that (i) certain behaviours can be used communicatively, (ii) carry distinct meaning linked to particular social contexts, and (iii) are produced to achieve distinct goals. However, further fine-grained analyses of great ape gestural production are necessary to reveal the form of gestures in relation to age, context and social partner.…”

“…If an asymptote was reached (i.e. no further gesture types were observed), we concluded that we had observed the individual's full repertoire for the communicative function of play solicitation [36]. …”

“…Moreover, there has been a strong bias towards studies on play signalling conducted on captive individuals [23,25,35]. Systematic, quantitative comparisons in natural environments taking into account within-species variability, that is including several communities, are still severely under-represented in research on great ape communication (however, see [36,37]).…”

“…We particularly focused on the single communicative function of play initiation only, since keeping the behavioural outcome (i.e. social play) constant enabled us to investigate gestures with the same meaning [36,38,39]. To allow for generalization of between- and within-individual comparison, behavioural data were collected in two distinct field periods per study site across two consecutive years.…”

“…To answer this question, we investigated whether the age and sex of signallers had an effect on the production of audible, tactile and visual gesturing (for categories, see [21]). Since it has been shown that young chimpanzees undergo a developmental shift from actions and tactile to visual [36,41] and audible gestural communication [40], we expected higher frequencies of audible and visual gestures with increasing age. In addition, studies on primates and some other mammal species revealed pronounced sex differences in play behaviour, showing that males engage in more play-fighting and play more vigorously than females (see for a review [42]).…”