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Comparative studies of animal communication systems are particularly important for understanding the origins and evolution of core features of human language like syntax and dialects. Recent studies have begun to develop bats as models for investigating shared traits with human language, given the complex social vocalizations of the former. Our previous research revealed that bat social calls contained almost 20 syllable types and the occurrence of these syllable types in the call sequences followed certain permutation rules. However, the differences in these patterns between populations remain unclear. Here, we examined the syntactic patterns of social calls in greater horseshoe bats, Rhinolophus ferrumequinum , from three geographically distant populations in China. The aggressive calls and behaviours during agonistic interactions of 26 bats were analysed to examine the consistency and variation between two aggression levels and across three populations. Common types of syllables, transitions and sequence patterns were found in all three populations. However, there were significant differences in the occurrence frequencies of shared syllable types, transition types and sequence types. Further, more noisy and composite syllables occurred when aggression was high than when it was low. There were also more transitions between noisy syllables and more repetitions in calls in a high aggression than in a low aggression context. The universal syntactic patterns and differences in social vocalizations of bats across different populations are of interest for fields of animal communication and language evolution. • Shared acoustic elements and patterns existed in social calls across populations. • Occurrence frequencies of vocalization types were different between populations. • High aggression calls were more noisy and complex than low aggression calls. [ABSTRACT FROM AUTHOR]

Echolocating bats observe their surroundings through continuous vocalization and echoreception. Sounds from nearby conspecifics may have a similar spectrum and high intensity. Bats emitting frequency-modulated (FM) echolocation calls avoid conspecific jamming sounds by altering their call frequency jamming avoidance response (JAR). Bats emitting constant frequency (CF)-FM can use other strategies to avoid jamming due to the different functions of the two acoustic components. In this study, seven Rhinolophus sinicus bats were used to conduct sound detection in both single individuals and pairs. We studied how these bats adjust the terminal FM (tFM) component of their calls when flying with conspecifics, and we tested whether acoustic adjustments are made to avoid jamming. Echolocation calls had shorter durations, reduced pulse intervals and higher tFM peak frequency and terminal frequency in the presence of conspecifics. The frequency differences of the tFM component between two bats did not increase in paired flights compared to their baseline difference, and the magnitude of spectral adjustments was independent of the baseline separations between bats. These results suggest that these bats do not use a JAR strategy to mitigate interference in the tFM component of calls. The call adjustments of CF-FM bats are more likely to be attention behaviours rather than being used for avoiding acoustic interference. Bats differentiate their own echoes and pulses from those of conspecifics through their respective acoustic signatures. • Spectral terminal FM adjustments in CF-FM bats do not assist jamming avoidance. • Call adjustments of bats in groups are more likely to be attention behaviours. • Bats identify their own calls from those of conspecifics via acoustic signatures. [ABSTRACT FROM AUTHOR]

Temperature and relative humidity are important environmental factors that greatly affect sound-mediated activities in animals. However, little is known about how changes in temperature and humidity affect animal vocal systems. Echolocating bats perceive their surroundings through acoustic signals. In this study, we investigated the effects of temperature and humidity changes on the audiovocal control system, Doppler shift compensation (DSC), in echolocating bats, Hipposideros armiger. Results revealed that the DSC system was more precise under higher temperature and humidity conditions, while the frequency of calls and echoes decreased under higher temperatures. Atmospheric attenuation and body temperature increased with increasing experimental temperature and humidity conditions. Our results suggest that atmospheric attenuation and body temperature significantly affect DSC precision (DSC P) and the specialized narrow-frequency band of the auditory system (reference frequency). Owing to the small differences in sound attenuation between experimental groups, we speculate that the changes in attenuation were not sufficient to induce changes in DSC P. We propose that DSC performance may change concomitantly with frequency adjustment and may be passively affected by body temperature regulation. Our study shows how changes in the weather can affect animal vocal control systems and fitness. • Doppler shift compensation is more precise at higher temperatures and humidity. • It may be affected by call frequency and body temperature changes. • Call frequency is affected by both body temperature and atmospheric attenuation. • The latter drives bats' call frequency changes when a physiological effect also exists. [ABSTRACT FROM AUTHOR]

Frequently, individuals of one species respond to alarm calls produced by another species. This form of interspecies communication can be critical for survival. How animals recognize and respond to heterospecific alarm calls is, however, still poorly understood. This is especially true for bats, which are highly vocal and possess a specialized auditory system. We hypothesized that, among bat species, acoustic similarity between heterospecific and conspecific alarm calls is a key factor that underlies call recognition. However, this ability could also be acquired via associative learning from prior exposure or result from phylogenetic relatedness among caller and receiver species, as shown by others. Here we focused on distress calls of bats as representing a certain type of alarm call. To test our hypothesis, we recorded distress calls of 11 bat species from four families at five different sites. We broadcast the recorded calls to three of these species (Rhinolophus sinicus , Myotis badius and Myotis laniger). For all three species, neither prior exposure (familiarity) nor phylogenetic relatedness explained the variation in the response strength, as measured by echolocation vocalizations of receiver species in response to playback of heterospecific distress calls. In contrast, acoustic similarity, especially in peak frequency, between conspecific and heterospecific distress calls, was positively correlated with response strength in the receiver species. Thus, our findings emphasize that, at least among bats, acoustic similarity is a key factor allowing recognition of heterospecific alarm calls. It remains unclear whether evolutionary, genetic and/or neurophysiological mechanisms entrain an individual to respond selectively to a specific acoustic feature. Highlights • We investigated recognition of heterospecific distress calls in bats. • The recognition of heterospecific distress calls is an unlearned behaviour. • Acoustic similarity elicits responses to heterospecific distress calls. • Peak frequency plays a key role in the response to heterospecific distress calls. [ABSTRACT FROM AUTHOR]