| Animal vocal communication includes signal sender,signal receiver,and acoustic signals.Acoustic signals play an important role in the survival and reproduction of animals.Many animals rely on acoustic signal predation,courtship,resist the enemy to identify conspecifics.Ambient noise is treated as an evaluative pressure on bats since it can reduce their detective ability for audio message.A relatively novel form of ambient noise is anthropologic noise.Bats are the only mammals that can fly.They use acoustic signals(echolocation pulses and social calls)to forage and communicate.Recent studies showed that bat have significant plasticity under different habitats and noise background.However,it’s unknown that how bats adjust their echolocation pluses and social calls to interact with anthropogenic noise.In this paper,we tested whether anthropogenic noise influence echolocation behavior and social calls using playback experiments in Asian parti-colored bat,Vespertilio sinensis,frequency of acoustic signals of whose overlap with anthropogenic noise.The main results were showed as follows:1.When Asian parti-colored bat flew freely in natural condition,they broadcasted multiple-harmonics echolocation pulses,in which first harmonic has most energy.We recorded the echolocation pulses from two groups of bats while flying in areas with two types of levels of traffic noise.The results showed that bats increased frequency(P < 0.05)and bandwith(P < 0.05)in high level noise to avoid noise interference.2.We recorded the echolocation pulses from two groups of bats flying in lab with broadcasting three types of anthropologic noise(levels:no stimulation、65 dB、75 dB,frequency:0-60 kHz).We found that Asian parti-colored bat produced multiple-harmonics echolocation pulses,in which the second harmonic has most energy.Bats emitted a lower frequency,longer duration and less slope echolocation pulses to interact with anthropologic noise increase.In contrast with situation without noise playback,duration(P < 0.05),bandwidth(P < 0.05)and slope in echolocation calls of bats(P < 0.05)increased in situation within a 60 dB anthropologic noise playback.However,start frequency didn’t differ significantly(P = 0.19),and end frequency decreased(P < 0.05)within a 60 dB anthropologic noise stimulation.Compared with the situation with 60 dB noise playback,spectral-temporal parameters of echolocation calls in bats changed within the playback of 70 dB anthropologic noise: longer duration(P < 0.05),lower end frequency(P < 0.05),wider bandwith(P < 0.05),steeper slope(P = 0.60),and similar start frequency(P = 0.19).3.In this study,female Asian parti-colored bat had a rich communication repertoire comprising 6 simple syllables(NB syllables,CF syllables and FM syllables)and 3 composites with harmonics in the ultrasonic range.4.We recorded the communication calls from two groups of bats in lab with broadcasting different anthropologic noise(levels:no stimulation、65 dB、75 dB,frequency:0 – 60 kHz).We found that Asian parti-colored bat increased frequency and duration of two syllables in noise group.Meanwhile,Asian parti-colored bat decreased vocal complexity in noise(P < 0.05).This change may make the call sequence become more monotonous,which is equivalent to increasing the repetition rate of syllables,in order to enhance the detection of vocal signals.In summarize,Asian parti-colored bat adjusted spectral/temporal parameters of echolocation and social calls,and decreased vocal complexity of social calls in respond to anthropologic noise.Our results show that vocal signal of Asian parti-colored bat have significant plasticity under anthropologic noise environment. |
