Acoustic signals are important to the biology of animals, mediating crucial activities such as social interactions (communication) as well as orientation and foraging (echolocation). Many signals used in communication are vocal, which are especially important in nocturnal animals such as bats where social interactions occur in darkness. Despite this, little is known about the social calls and behaviours of echolocating bats. To better understand their social and acoustic behaviour, we compiled an ethogram and list of vocalisations for Geoffroy's horseshoe bat (Rhinolophus clivosus). We kept three non-contemporaneous and short-term captive groups to capture interactions and social calls using simultaneous video and audio recordings. The resultant ethogram was comprised of 40 unique types of behaviour, both social and non-social. Social calls (n = 255) were assigned to different call types by their frequency-time contour and categorised by their behaviours, situational categories and functional contexts (affiliative or agonistic). From the calls observed, four acoustically distinct call types were identified: (i) cascading/rising frequency-modulated (FM) calls (n = 26), (ii) oscillatory FM calls (n = 140), (iii) noisy screech calls (n = 68), and (iv) whistle calls (n = 21) (GLM: F30, 711 = 24.28, P < 0.001). Call types showed only weak associations with certain behaviours, situational categories or functional contexts. However, calls with specific acoustic attributes accompanied the behaviour of wing swat [discriminant function analysis (DFA) classification success: 76%; GLM: F20, 108 = 4.12, P < 0.001] and situational category of flight (DFA classification success: 82%; GLM: F20, 136 = 2.97, P < 0.001). An analysis of acoustic attributes across all call types showed weak associations with functional context (Affiliative DFA classification success: 6%). Only one acoustic parameter (peak frequency) had a slight significant difference between calls emitted during agonistic and affiliative interactions (GLM: F10, 73 = 2.30, P < 0.05; post-hoc unequal n: P = 0.044). In addition to the description of distinct call types, we provide evidence of transitional calls in this bat species in which a social call transitions seamlessly into an echolocation pulse. This study gives a first glimpse into the behaviours and social vocalisations produced by R. clivosus. Basic behavioural data such as these may facilitate the design of experiments that allow greater insight into the social organisation of bats.
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Vol. 20 • No. 2