Evolutionary biologists have a long-standing interest in how acoustic signals in animals vary geographically,because divergent ecology and sensory perception play an important role in speciation.Geographic comparisons are valuable in determining the factors that influence divergence of acoustic signals.Bats are social mammals and they depend mainly on echolocation pulses to locate prey,to navigate and to communicate.Mounting evidence shows that geographic variation of bat echolocation pulses is common,with a mean 5-10 kHz differences in peak frequency,and a high level of individual variation may be nested in this geographical variation.However,understanding the geographic variation of echolocation pulses in bats is very difficult,because of differences in sample and statistical analysis techniques as well as the variety of factors shaping the vocal geographic evolution.Geographic differences in echolocation pulses of bats generally lack latitudinal,longitudinal and elevational patterns,and little is known about vocal dialects.Evidence is accumulating to support the fact that geographic variation in echolocation pulses of bats may be caused by genetic drift,cultural drift,ecological selection,sexual selection and social selection.Future studies could relate geographic differences in echolocation pulses to social adaptation,vocal learning strategies and patterns of dispersal.In addition,new statistical techniques and acoustic playback experiments may help to illustrate the causes and consequences of the geographic evolution of echolocation pulse in bats.
Vocal communication plays an important role for individual recognition and male-female interaction during mating in greater horseshoe bats,especially in respect to mate fidelity,which ensures that the bats can maintain a stable social organization.Few studies,however,have addressed the calling behavior during copulating in bats.Here,we initially report the copulation vocalizations and behaviors of both male and female greater horseshoe bats.During copulation,the male assumed a dorsal position and arched his back,arming around the female using his feet and thumbs.The male repeatedly produced very short constant frequency(SCF) syllables with high intensity and repetition rate(male 1:16.48±4.8 ms,male 2:17.79±4.03 ms) when he tried to insert the penis into the female,and then long syllables(male 1:42.08±12.67 ms,male 2:43.02±11.44 ms) after penile insertion.The female bats sometime refused the male bats in the early phase of copulations as emitting noise bursts and broad-band vocalizations,but kept silence during actual copulation.We also found that the SCF copulation calls of one male remained stable peak frequencies on different copulation days although its echolocation call frequency varied each day.Moreover,different male individuals maintained their own "private frequency" in the SCF copulation calls.Therefore,we predicted that the SCF copulation calls may serve as an indicator for female greater horseshoe bats to recognize the mating males in order to maintain mate fidelity because horseshoe bats exhibit sexual segregation before mating.Our results stipulate further studies on mating system and copulation strategies in polygynous bats.Such work may also aid in promoting the preservation of greater horseshoe bats.
