Context-related call combinations in female Diana monkeys

Abstract

Non-human primates possess species-specific repertoires of acoustically distinct call types that can be found in adults in predictable ways. Evidence for vocal flexibility is generally rare and typically restricted to acoustic variants within the main call types or sequential production of multiple calls. So far, evidence for context-specific call sequences has been mainly in relation to external disturbances, particularly predation. In this study, we investigated extensively the vocal behaviour of free-ranging and individually identified Diana monkeys in non-predatory contexts. We found that adult females produced four vocal structures alone ('H', 'L', 'R' and 'A' calls, the latter consisting of two subtypes) or combined in non-random ways ('HA', 'LA' and 'RA' call combinations) in relation to ongoing behaviour or external events. Specifically, the concatenation of an introductory call with the most frequently emitted and contextually neutral 'A' call seems to function as a contextual refiner of this potential individual identifier. Our results demonstrate that some non-human primates are able to increase the effective size of their small vocal repertoire not only by varying the acoustic structure of basic call types but also by combining them into more complex structures. We have demonstrated this phenomenon for a category of vocalisations with a purely social function and discuss the implications of these findings for evolutionary theories of primate vocal communication.

Formal monkey linguistics

“…Following Candiotti et al (2012), they show that the social calls of Diana monkey females arguably include complex calls as well. First, some of the calls are produced in what Candiotti et al (2012) term merged association; this means that there is no discernible pause between the two calls. Thus in addition to individual calls L, H, R, A, the repertoire contains 2-call units LA, HA, and RA.…”

Semantic communication in birds: evidence from field research over the past two decades

“…For example, puttynosed monkeys (Cercopithecus nictitans) produce the acoustically discrete loud calls ''pyow'' and ''hack'' in a range of contexts, but combine the two calls when instigating group movements Zuberbu¨hler 2006a, 2008). Similarly, some other Old World monkeys (Cercopithecinae) (Ouattara et al 2009;Candiotti et al 2012), New World monkeys (Pitheciidae) (Ca¨sar et al 2013), and apes (Hominidae) (Crockford and Boesch 2005;Zuberbu¨hler 2009, 2011) can combine different types of calls into a variety of sequences and use these combinations in different environmental contexts, such as the discovery of food sources or encounters with predators.…”

Formal monkey linguistics: The debate

“…The male Campbell's root + suffix (-oo) structure is a 1-merge system, with the constraint that -oo does not occur on its own. Diana female social calls might be another instantiation of this system (Veselinović et al 2014;Candiotti et al 2012;Coye et al 2016). The jury is still out concerning the status of Colobus snort-roar sequences.…”

“…Notably, in Campbell's monkeys the suffix -oo can be added to two roots, krak and hok (see Ouattara et al 2009a;Kuhn et al 2014 for recent discussion); and it is plausible that it modifies the meaning of the root in the same way in both cases (on one theory, R-oo indicates that one should be in the same attentional state as if R had been uttered -hence a broader meaning; on a competing theory, R-oo indicates that there is a weak threat of the type that licenses R -hence a narrower meaning). In Diana monkeys, the A-call has root uses, but it also arguably serves to form the complex calls LA, HA, and RA, which are targeted as units by the operation of repetition, thus yielding LA LA LA LA (Veselinović et al 2014;Candiotti et al 2012; see also Coye et al 2016 for field experiments with artificial playbacks, showing that the A suffix provides information about caller identity while the first part of LA and RA complex calls provides information about the social and physical context. 7 )…”