Vocal production learning in the pale spear-nosed bat, Phyllostomus discolor

Abstract

Vocal production learning (VPL), or the ability to modify vocalizations through the imitation of sounds, is a rare trait in the animal kingdom. While humans are exceptional vocal learners, few other mammalian species share this trait. Owing to their singular ecology and lifestyle, bats are highly specialized for the precise emission and reception of acoustic signals. This specialization makes them ideal candidates for the study of vocal learning, and several bat species have previously shown evidence supportive of vocal learning. Here we use a sophisticated automated set-up and a contingency training paradigm to explore the vocal learning capacity of pale spear-nosed bats. We show that these bats are capable of directional change of the fundamental frequency of their calls according to an auditory target. With this study, we further highlight the importance of bats for the study of vocal learning and provide evidence for the VPL capacity of the pale spear-nosed bat.

Acoustic allometry and vocal learning in mammals

“…intra-sexual [57] fo [58] non-significant body mass-peak frequency relationship across species [59] yes [25,58,60] Saccopteryx bilineata (greater sac-winged bat)…”

Vocal plasticity in harbour seal pups

“…The present experiment setting was not designed to induce imitative behaviour or a specific vocalisation change (for example by rewarding a specific vocal parameter shift [26, 47, 48]). Instead, our playback triggered a spontaneous and volitional vocal response.…”

“…The present experiment setting was not designed to induce imitative behaviour or a specific vocalisation change (for example by rewarding a specific vocal parameter shift [26,47,48]). In humans vocal learning requires control, mediated by the laryngeal motor cortex, over multiple phonatory structures linked to both the source and the filter [90].…”

“…Few studies have demonstrated the capacity of fine F0 modulation [42, 43], sometimes coinciding with vocal imitation (elephants: [44, 45]). Some bats are capable of vocal imitation [46] and pale spear-nosed bats ( Phyllostomus discolor) can be trained to shift their F0 downwards [47, 48]. Birds increase their F0s in urban environments due to low frequency traffic noise [49].…”

Do Bats Have the Necessary Prerequisites for Symbolic Communication?

“…Imitating new signals is one form of vocal production learning (VPL), modifying existing signals based on social influences is another ( Janik and Slater, 1997 , 2000 ). VPL via social modification has been shown for social calls ( Rousettus aegyptiacus : Prat et al, 2015 , 2017 ; Genzel et al, 2019 ; Saccopteryx bilineata : Knörnschild et al, 2012 ; Phyllostomus discolor : Esser and Schmidt, 1989 ; Esser, 1998 ; Lattenkamp et al, 2020 ; P. hastatus : Boughman, 1998 ) and echolocation calls ( Rhinolophus ferrumequinum : Jones and Ransome, 1993 ; Hipposideros terasensis : Hiryu et al, 2006 ). In addition to VPL, vocal usage learning has been demonstrated by training temporarily isolated bats to vocalize in order to trigger a food reward ( P. discolor : Lattenkamp et al, 2018 ).…”