Campbell's Monkeys Use Affixation to Alter Call Meaning

Abstract

Human language has evolved on a biological substrate with phylogenetic roots deep in the primate lineage. Here, we describe a functional analogy to a common morphological process in human speech, affixation, in the alarm calls of free-ranging adult Campbell's monkeys (Cercopithecus campbelli campbelli). We found that male alarm calls are composed of an acoustically variable stem, which can be followed by an acoustically invariable suffix. Using long-term observations and predator simulation experiments, we show that suffixation in this species functions to broaden the calls' meaning by transforming a highly specific eagle alarm to a general arboreal disturbance call or by transforming a highly specific leopard alarm call to a general alert call. We concluded that, when referring to specific external events, non-human primates can generate meaningful acoustic variation during call production that is functionally equivalent to suffixation in human language.

Context-related call combinations in female Diana monkeys

“…When compared to previous studies in closely related species, the combinatorial system of social calls in Diana monkeys showed some parallels with the affixation system in Campbell's monkeys (Ouattara 2009a), although a number of important differences were also present. Specifically, there was no evidence that Diana monkeys' combinations of social calls carried strong semantic content relating to specific events, such as a falling tree, the approach of a neighbouring group (Ouattara et al 2009b) or a signal for group progression (Arnold and Zuberbühler 2006).…”

“…Data were collected between 07:30 and 17:00 h GMT. Every 30 min, a scan sample (Altmann 1974) was taken on a number of variables that, according to previous studies, had the potential to influence the monkeys' vocal behaviour (Ouattara et al 2009a). Specifically, we scored the location of the group within its territory (using a map and a grid system), the degree of group scattering, the group's main activity, general luminosity and the presence of a neighbouring Diana monkey group (Table 1).…”

“…For example, male putty-nosed monkeys (C. nictitans) combine two types of loud calls into sequences that reliably predict forthcoming group progression (Arnold and Zuberbühler 2008). Similarly, male Campbell's monkeys (C. campbelli) transform highly specific alarm calls into general alert calls by an affixation mechanism (Ouattara et al 2009a) and concatenate individual calls into sequences that are context-specific and related to external events (Ouattara et al 2009b). However, a largely unaddressed question is whether close-range social calls in primates show similar or even increased flexibility in terms of acoustic properties and sequential structure, as hypothesised by Lemasson and Hausberger (2011).…”

Vocal repertoire of free‐ranging adult golden snub‐nosed monkeys (Rhinopithecus roxellana)

“…The level of gradedness or discreteness is likely to be varied among different call types depending on their specific functions (Bouchet et al, 2013; Lemasson & Hausberger, 2011). In C. campbelli , for example, male alarm call types appear to be discrete, whereas female contact call types exhibit a high degree of variation (Lemasson & Hausberger, 2011; Ouattara, Lemasson, & Zuberbühler, 2009). …”

Le langage n’est pas le propre de l’homme, « parole » de singes !

“…Nous étudions, depuis une dizaine d'années, le comportement vocal de la mone de Campbell, à la fois en captivité (centre de primatologie de l'université de Rennes 1) et dans la nature ( (Figure 1) [8]. Alors que Krak et Hok encodent un message d'alarme sur la perception d'un prédateur, respectivement « léopard » et « aigle », l'ajout du suffixe « oo » généralise le message en « danger provenant du sol » (Krakoo) ou « de la canopée » (Hokoo).…”