In-flight social calls: a primer for biologists and managers studying echolocation

Abstract

Recent technological advances have permitted collection of immense data sets through automated recordings that are primarily aimed at capturing bat echolocation. Analyses of echolocation calls are used to identify species, relative abundance, and some aspects of behaviour, such as foraging or commuting. Here we propose that social calls recorded in flight are also valuable tools for understanding bat ecology and behaviour. First, we examine how and why the acoustic structure of social calls differ from echolocation. Differences in form make social calls often, but not always, easy to identify. We then use a case study on in-flight song in Brazilian free-tailed bat (Tadarida brasiliensis (I. Geoffroy, 1824)) to show that what may appear as echolocation may instead be predominantly used for social communication. Next, we review three basic functions of in-flight social calls, including examples of each, and develop a framework for testing these alternative functions using automated recordings. In a second case study, we use automated recordings of the endangered Florida bonneted bat (Eumops floridanus (G.M. Allen, 1932)) to illustrate how behavioural information can be gleaned by examining patterns of social call production. Finally, we discuss why and how social calls provide novel information that can be crucial for conservation and management efforts.