Responsiveness to conspecific distress calls is influenced by day-roost proximity in bats (Saccopteryx bilineata).

Maria Eckenweber,Mirjam Knörnschild

doi:10.1098/rsos.160151

Abstract

Distress calls signal extreme physical distress, e.g. being caught by a predator. In many bat species, distress calls attract conspecifics. Because bats often occupy perennial day-roosts, they might adapt their responsiveness according to the social relevance in which distress calls are broadcast. Specifically, we hypothesized that conspecific distress calls broadcast within or in proximity to the day-roost would elicit a stronger responsiveness than distress calls broadcast at a foraging site. We analysed the distress calls and conducted playback experiments with the greater sac-winged bat, Saccopteryx bilineata, which occupies perennial day-roosts with a stable social group composition. S. bilineata reacted significantly differently depending on the playback's location. Bats were attracted to distress call playbacks within the day-roost and in proximity to it, but showed no obvious response to distress call playbacks at a foraging site. Hence, the bats adapted their responsiveness towards distress calls depending on the social relevance in which distress calls were broadcast. Distress calls within or in proximity to the day-roost are probably perceived as a greater threat and thus have a higher behavioural relevance than distress calls at foraging sites, either because bats want to assess the predation risk or because they engage in mobbing behaviour.

Highlights

Distress calls appear in the vocal repertoire of different taxa and are defined as vocalization given in situations of extreme distress, like being caught by a predator or in a trap [1]
We found three different categories of distress calls in S. bilineata
The majority of S. bilineata distress calls are low frequency, and have noisy components and a large bandwidth, making distress calls audible for conspecifics and various hearing predators such as primates, coatis, raptors and toucans

Summary

Introduction

Distress calls appear in the vocal repertoire of different taxa and are defined as vocalization given in situations of extreme distress, like being caught by a predator or in a trap [1]. Distress calls have a similar acoustic design across taxa Primates; [3]: rodents; [4]: deer; [5]: bats; [6]: frogs). They can be generally described as low-frequency 2 calls, often with noisy parts and a large bandwidth, making them audible over a larger distance [2,7,8]. Distress calls are only produced under the physical stress of an actual attack (and are sometimes called fear screams), whereas alarm calls or alert calls are used to warn conspecifics prior to an attack [9]

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Conclusion