Abstract
Vocal learning, the substrate of human language acquisition, has rarely been described in other mammals. Often, group-specific vocal dialects in wild populations provide the main evidence for vocal learning. While social learning is often the most plausible explanation for these intergroup differences, it is usually impossible to exclude other driving factors, such as genetic or ecological backgrounds. Here, we show the formation of dialects through social vocal learning in fruit bats under controlled conditions. We raised 3 groups of pups in conditions mimicking their natural roosts. Namely, pups could hear their mothers' vocalizations but were also exposed to a manipulation playback. The vocalizations in the 3 playbacks mainly differed in their fundamental frequency. From the age of approximately 6 months and onwards, the pups demonstrated distinct dialects, where each group was biased towards its playback. We demonstrate the emergence of dialects through social learning in a mammalian model in a tightly controlled environment. Unlike in the extensively studied case of songbirds where specific tutors are imitated, we demonstrate that bats do not only learn their vocalizations directly from their mothers, but that they are actually influenced by the sounds of the entire crowd. This process, which we term “crowd vocal learning,” might be relevant to many other social animals such as cetaceans and pinnipeds.
Highlights
Vocal learning, the ability to learn to produce vocalizations by hearing, is essential in human language acquisition, but only a few other mammals appear to possess this capability [1,2,3,4,5,6,7,8]
The recognition of vocal dialects among different populations can open a window on the vocal learning abilities of animals, but such findings in the wild may reflect genetic or ecological differences between groups rather than the learning of group-specific vocal behavior
Some indications for the existence of vocal learning in nonhuman animals arise from the observation of group-specific vocal dialects in wild populations [9,10,11]
Summary
The ability to learn to produce vocalizations by hearing, is essential in human language acquisition, but only a few other mammals appear to possess this capability [1,2,3,4,5,6,7,8]. Some indications for the existence of vocal learning in nonhuman animals arise from the observation of group-specific vocal dialects in wild populations [9,10,11]. Geographic variations in vocalizations of these 2 species were observed [15,16], though genetic and environmental factors were not excluded as possible contributors to these apparent dialects. In another bat species (Saccopteryx bilineata) that is an important model for vocal learning, pups have been shown to learn territorial songs from adult male tutors [17] and to engage in vocal babbling behavior [18]. We have previously shown that this process involves vocal learning [19]
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