Distress Calls of a Fast-Flying Bat (Molossus molossus) Provoke Inspection Flights but Not Cooperative Mobbing

Abstract

Many birds and mammals produce distress calls when captured. Bats often approach speakers playing conspecific distress calls, which has led to the hypothesis that bat distress calls promote cooperative mobbing. An alternative explanation is that approaching bats are selfishly assessing predation risk. Previous playback studies on bat distress calls involved species with highly maneuverable flight, capable of making close passes and tight circles around speakers, which can look like mobbing. We broadcast distress calls recorded from the velvety free-tailed bat, Molossus molossus, a fast-flying aerial-hawker with relatively poor maneuverability. Based on their flight behavior, we predicted that, in response to distress call playbacks, M. molossus would make individual passing inspection flights but would not approach in groups or approach within a meter of the distress call source. By recording responses via ultrasonic recording and infrared video, we found that M. molossus, and to a lesser extent Saccopteryx bilineata, made more flight passes during distress call playbacks compared to noise. However, only the more maneuverable S. bilineata made close approaches to the speaker, and we found no evidence of mobbing in groups. Instead, our findings are consistent with the hypothesis that single bats approached distress calls simply to investigate the situation. These results suggest that approaches by bats to distress calls should not suffice as clear evidence for mobbing.

Asymmetric Response to Heterotypic Distress Calls in the Lizard Liolaemus chiliensis

“…), or a learning process (Conover ; Griffin ; Carter et al. ), although there is no independent evidence of such behavior in Liolaemus .…”

“…The opportunity for prey individuals to reduce their own predation risk by responding to the alert message of distress calls would be a strong selective pressure for the evolution of eavesdropping on heterospecific calls (Carter et al. ; Magrath et al. ).…”

“…; Carter et al. ), and these can vary ontogenetically (Martins & Haddad ), individually (Franzen & Glaw ; Lingle et al. ), or geographically (Sicuro et al.…”

Vocal sequences suppress spiking in the bat auditory cortex while evoking concomitant steady-state local field potentials

“…When under duress or when in the presence of danger, most vertebrate species produce sounds that (among other functions) serve to advertise the ongoing discomfort situation. Calls uttered in distress circumstances are known as “distress calls”, “alarm calls”, or “screams”234567891011, and they have profound effects in the listeners’ physiology and behaviour, such as boosting gene expression, elevating heart-rate, activating the neuroendocrine axis, and evoking exploratory and mobbing behaviours in conspecifics5679101213141516171819202122.…”

Does Interspecific Eavesdropping Promote Aerial Aggregations in European Pipistrelle Bats During Autumn?

“…; Carter et al. ), or that the broadcast of social calls increases capturing success at mist nets (Hill & Greenaway ; Goiti et al. ; Loeb & Britzke ; Hill et al.…”