Suffixation influences receivers' behaviour in non-human primates

Abstract

Compared to humans, non-human primates have very little control over their vocal production. Nonetheless, some primates produce various call combinations, which may partially offset their lack of acoustic flexibility. A relevant example is male Campbell's monkeys (Cercopithecus campbelli), which give one call type ('Krak') to leopards, while the suffixed version of the same call stem ('Krak-oo') is given to unspecific danger. To test whether recipients attend to this suffixation pattern, we carried out a playback experiment in which we broadcast naturally and artificially modified suffixed and unsuffixed 'Krak' calls of male Campbell's monkeys to 42 wild groups of Diana monkeys (Cercopithecus diana diana). The two species form mixed-species groups and respond to each other's vocalizations. We analysed the vocal response of male and female Diana monkeys and overall found significantly stronger vocal responses to unsuffixed (leopard) than suffixed (unspecific danger) calls. Although the acoustic structure of the 'Krak' stem of the calls has some additional effects, subject responses were mainly determined by the presence or the absence of the suffix. This study indicates that suffixation is an evolved function in primate communication in contexts where adaptive responses are particularly important.

Meaningful call combinations and compositional processing in the southern pied babbler

“…To rule out alternative explanations associated with the saliency of the stimulus (two vs. one call type) or priming effects (any call type preceding recruitment calls generates the same response), we implemented an additional important control condition, where we artificially replaced the alert call of a mobbing sequence with another acoustically distinct broadband babbler vocalization: the foraging "chuck" call (chuck recruitment sequence) (Supporting Information) (24,32,33). Finally, in line with previous studies (12,13), to ensure that the key dimension for receivers was the combination of information and not any urgency-based acoustic variation encoded across the structure, as an additional control, artificial mobbing sequences were constructed from the independent calls and played back (Supporting Information and Table S1) (13,32). Our playbacks revealed differences in group attentiveness responses to the four playback conditions determined by the proportion of the group that became vigilant (treatment: χ 2 = 53.5; P < 0.01; n = 64; 16 groups) ( Fig.…”

“…Male Campbell's monkeys (Cercopithecus campbelli), for example, produce predator-specific alarm calls that can be affixed with an acoustic modifier (8,11). The affix acts to alter the "meaning" of the alarm calls in a predictable way, transforming them into general disturbance calls (8,11,12). Similarly, male putty-nosed monkeys (Cercopithecus nictitans) combine two predator-specific alarm calls into a higher-order sequence (9,13).…”

The origins of gestures and language: history, current advances and proposed theories

“…Second, protogrammar rules that reflect similarities with grammatical principles of human language (morphology and syntax) have been identified in primate vocal communication, namely morpho‐syntax shown by sound units which may be merged to form complex (suffixed) calls (e.g. Crockford & Boesch, ; Candiotti, Zuberbühler & Lemasson, ; Coye et al ., , ; Coye, Zuberbühler & Lemasson, ) or calls that can be combined into vocal sequences with a context‐dependent predictable concatenation pattern allowing animals to refine or enrich the information conveyed [e.g. Clarke, Reichard & Zuberbühler, ; Arnold & Zuberbühler, ; Ouattara, Lemasson & Zuberbühler, ; see also Collier et al ., for a review concerning the combinatorial structure of human and animal vocal systems].…”

Syntax manipulation changes perception of mobbing call sequences across passerine species

“…In animals, vocalizations involve a far less complex level of organization than human language. Although more and more evidence for syntax is becoming available for some birds and mammals (Coye, Ouattara, Zuberbühler, & Lemasson, ; Ouattara, Lemasson, & Zuberbühler, ), the ability of species to use compositional syntax (or compositionality; see Suzuki, Griesser, & Wheatcroft, ) is still debated (Bolhuis, Beckers, Huybregts, Berwick, & Everaert, ; Petkov & Jarvis, ; Petkov & Wilson, ; Suzuki, Wheatcroft, & Griesser, ). More recently, three studies have examined this issue by studying mobbing calls produced by the Japanese tit, Parus minor , and the southern pied babbler, Turdoides bicolor (Engesser, Ridley, & Townsend, ; Suzuki, Wheatcroft, & Griesser, , ).…”