Characteristic And Geographic Variation Of Social Vocalizations Of FM Bats

Studies reveal significant influence of the characteristic of communication calls and behavioral plasticity on the motivation of animal vocalizations, which provide the ethological evidence on expression of emotions in animals. Many bat species live in dark environments and produce complicated social vocalization to facilitate social interactions, and thus bats are well suited for investigating vocal diversity as well as behavioral plasticity. Recent researches on communication calls mainly focused on CF and CF-FM bats, and studies combining behavioral and acoustic analyses of social calls are relatively lacking in FM bats which individuals interact frequently, so communication calls may play a more important role in maintaining the social stability.This research selected the representative FM bats—the greater tube-nosed bats(Murina leucogaster) and the fishing bat(Myotis pilosus) to perform simultaneous recording of vocalizations and social behavior, and revealed the spectral characteristics, vocal diversity and behavioral motivation, as well as tested the function of echolocation pulses emitted during foraging in social communication and. At the same time, aggressive behavior as the common behavioral context was used to illustrate the variation of bat aggressive signals from the individual and population level in detail. The main contents were as follows:1. Recording of vocalization and social behavior in Murina leucogaster reveals this bat species has a rich communication repertoire comprising 12 simple syllables(2 NB syllables,2CF syllables and 8 FM syllables) and 5 composites with harmonics in the ultrasonic range.The fundamental frequencies of vocalizations ranged from 17.09 to 107.20 k Hz and durations from 1.36 to 185.50 ms.2. The data suggest that structurally simpler components can be recombined within behaviorally meaningful and multifunctional contexts, such as: flight, contact, distress,aggressive, approach, mating or grooming contexts, indicating behavioral plasticity of communication calls. Spectral characteristics, such as noisy, low frequency calls(most of which include the NB element) and of tonal, high frequency calls(most of which include l DFM) can reveal animal vocal motivation, which support Morton’s motivation-structure hypothesis.3. Two echolocation-like syllable types exist in Murina leucogaster. l DFM: The whole spectrogram shifted downward to lower frequency space and the average peak frequency of the fundamental was 45.72 k Hz; c DFM: The spectrogram resembled a vertically flipped check mark and the average start frequency of the fundamental was 152.02 ± 10.73 k Hz.Behavioral observation revealed the presence of modified components of echolocation pulses embedded within communication calls and might falicate social function.4. Behavioral and acoustic recording was performed in macro-geographic range(including all mainland lineages: Yangtze Plain, Sichuan Basin as well as North and South of China) from five populations(Fangshan in Beijing, Lu’an in Anhui, Dazhou and Mianyang in Sichuan and Yongzhou in Hunan). We found the fishing bat, Myotis pilosus, mainly produced three types of aggressive calls with tonal and noisy burst elements: AFM simple monosyllabic call(a), NB-DFM simple monosyllabic call(b) and NB-DFM simple multisyllabic call(c).5. The results of Nested analysis of variance(Nested ANOVA), Multi factor analysis of variance(MNOVA) and Discriminant function analysis(DFA) revealed that there existed the significant differences(all P < 0.05) of spectrotemporal parameters of aggressive calls in individual level. This result indicates that these calls contain sufficient variation to encode an individual, which may allow bats for individual discrimination or recognization. No significant differences were detected across the five geographic populations in acoustic parameter of each call type with the exception of duration of AFM simple monosyllabic call(F4, 39 = 4.27,P = 0.0068). These results show that aggressive calls of this bat species tend to evolutionary similarity.