Behaviour, biology and evolution of vocal learning in bats

Abstract

The comparative approach can provide insight into the evolution of human speech, language and social communication by studying relevant traits in animal systems. Bats are emerging as a model system with great potential to shed light on these processes given their learned vocalizations, close social interactions, and mammalian brains and physiology. A recent framework outlined the multiple levels of investigation needed to understand vocal learning across a broad range of non-human species, including cetaceans, pinnipeds, elephants, birds and bats. Here, we apply this framework to the current state-of-the-art in bat research. This encompasses our understanding of the abilities bats have displayed for vocal learning, what is known about the timing and social structure needed for such learning, and current knowledge about the prevalence of the trait across the order. It also addresses the biology (vocal tract morphology, neurobiology and genetics) and evolution of this trait. We conclude by highlighting some key questions that should be answered to advance our understanding of the biological encoding and evolution of speech and spoken communication. This article is part of the theme issue 'What can animal communication teach us about human language?'

Keywords: Chiroptera; FoxP2; language; neurobiology; speech; vocal production learning.

Figure 1.

Framework for studying vocal learning [4]. Left panels identify overarching questions at each level and the associated fields of the study. Right panels indicate some key questions within each field that are a priority to address in bats. (Online version in colour.)

Figure 2.

Evidence for bat vocal learning mapped to the bat family tree. Behavioural studies relevant for vocal learning (table 1) have been categorized as ‘consistent with vocal learning’ (found within eight families) or ‘direct evidence for vocal learning’ (found within five of those families). ‘Consistent with vocal learning’ = adult call similarity, geographical variation, group differences. ‘Direct evidence for vocal learning’ = adult call convergence, adult call shift, juvenile call convergence, juvenile call shift or juvenile-adult similarity. Tree adapted from Teeling et al. [56]. (Online version in colour.)