Characteristics of Calls of Woolly Horseshoe Bat Rhinolophus luctus and Intermediate Horseshoe Bat R.affinis During Parturition
[Objectives]Acoustic signals play a crucial role in transmitting information and maintaining social stability in animals,especially in gregarious bats which are considered to occupy the ecological niche of the night sky and rely primarily on biological sonar for navigating in the dark.Acoustic signals mediate a variety of life history events in nocturnal bats,including reproduction,foraging,communication and spatial navigation.The parturition is a crucial part of animal reproductive activity,directly determining the survival of offspring and their female parent.There has been little research on the parturition behavior of wild animals,particularly the vocalizations during parturition.In the present study,we aim to document the social vocal repertoire of Rhinolophus luctus and R.affinis during parturition.[Methods]We caught the pregnant bats with mist net or hand net from a nursery colony in Nanyang,Henan Province.All bats were taken into a temporary laboratory near the roost,and then were given mealworms and water.Vocalizations were picked up with the ultrasonic acquisition system using a sample rate of 250 kHz at 16 bits/sample.The pregnant bat's behavior was monitored via an infrared camera.We measured 8 spectro-temporal parameters from the oscillogram and spectrogram to quantify syllable features(Table 1 and 2).Then multiple statistical analyses were conducted to map the acoustic boundaries of different syllables.[Results]A total of 89 syllables were obtained,among which 6 and 4 types were distinguished from the Woolly Horseshoe Bat and the Intermediate Horseshoe Bat,respectively(Fig.1).The cumulative sum of the two largest eigenvalues(corresponding to the first two principal components)obtained from the principal components analysis explained 71.36％of the total variation(Table 3).Based on the results of the discriminant function analyses associated with a subset-validation procedure,40.5％of syllable types were correctly classified,which was significantly higher than expected by chance(Fig.2a).Multidimensional scaling of mean values of multiple parameters further confirmed notable differences among these syllables in a three-dimensional space(Fig.2b).In addition,Euclidean distance analysis showed that there were more significant differences between interspecific relationship than intraspecific relationship(Table 4).[Conclusion]Our results indicate that these two bat species use relatively variant social vocalizations with different spectro-temporal features during parturition.Altogether,the data will provide a reference for further work on the function and vocal mechanisms of acoustic communication in nocturnal mammals.
Rhinolophus luctusR.affinisSocial callsParturitionSpectro-temporal features
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