Vocal convergence in a multi-level primate society: insights into the evolution of vocal learning

Abstract

The extent to which nonhuman primate vocalizations are amenable to modification through experience is relevant for understanding the substrate from which human speech evolved. We examined the vocal behaviour of Guinea baboons, Papio papio , ranging in the Niokolo Koba National Park in Senegal. Guinea baboons live in a multi-level society, with units nested within parties nested within gangs. We investigated whether the acoustic structure of grunts of 27 male baboons of two gangs varied with party/gang membership and genetic relatedness. Males in this species are philopatric, resulting in increased male relatedness within gangs and parties. Grunts of males that were members of the same social levels were more similar than those of males in different social levels ( N = 351 dyads for comparison within and between gangs, and N = 169 dyads within and between parties), but the effect sizes were small. Yet, acoustic similarity did not correlate with genetic relatedness, suggesting that higher amounts of social interactions rather than genetic relatedness promote the observed vocal convergence. We consider this convergence a result of sensory–motor integration and suggest this to be an implicit form of vocal learning shared with humans, in contrast to the goal-directed and intentional explicit form of vocal learning unique to human speech acquisition.

A cross-species framework to identify vocal learning abilities in mammals

“…Although recent work calls for careful adjustments in categorizing vocal learning abilities along a multidimensional space [ 12 ], we applied a conservative approach in our choice to characterize species as vocal learners. We excluded, for instance, cases of vocal convergence, seen in Guinea baboons [ 11 ] and chimpanzees [ 21 ], although these could be considered part of a broad vocal learning contiguum [ 12 ]. We, therefore, classified as vocal learners the species that belong to the four non-human mammalian clades for which vocal learning has been shown in the form of VPL.…”

“…Second, selective pressures may also have favoured the emergence of vocal learning abilities without necessarily affecting acoustic allometry relationships. For instance, Fischer et al [11] recently demonstrated that vocal convergence in Guinea baboons was dependent on the amount of social interactions between individuals, therefore showing that some implicit forms of vocal learning can likely originate from social factors, and that allometry scaling need not be affected for a species to exhibit vocal learning abilities. In addition to confirming other vocal convergence results in this clade [21], Fischer et al's study also reaffirms the need to consider vocal learning as a multidimensional space transcending the limitation of vocal learning to 'vocal production learning', even when the latter is thought of as a continuum [11,12].…”

Vocal production learning in mammals revisited

“…The main body of recent evidence for vocal flexibility in nonhuman primates comes from studies on vocal convergence within call types ( figure 1 ). Several studies reported greater acoustic similarities between closely associated animals that were not genetically related than between non-associates, including grey mouse lemurs ( Microcebus murinus ) [ 73 ], Campbell's monkeys ( Cercopithecus campbelli ) [ 74 ], Guinea baboons ( Papio papio ) [ 75 ] ( figure 2 c ) and chimpanzees ( Pan troglodytes ) [ 76 ]. To further investigate the process of convergence, studies have documented call characteristics before and after housing animals with previously unknown conspecifics.…”

“…Guinea baboons (Papio papio) [75] (figure 2c) and chimpanzees (Pan troglodytes) [76]. To further investigate the process of convergence, studies have documented call characteristics before and after housing animals with previously unknown conspecifics.…”

Localize Animal Sound Events Reliably (LASER): A New Software for Sound Localization in Zoos

“…Animal sounds can also be used as indicators of social relationships. For example, for some primate species, certain call types are known to correlate with social ranks within the group [12][13][14]. In terms of animal welfare, vocalizations can also be used as indicators.…”