Studies On The Interspecific Recognition And Response Of Sympatric Bats Via Territorial Calls

The territory is the crucial resource associated with survival and reproduction of animals,which leads to frequent occurrence of territorial competition within and between species.Territorial signals can reduce the possibility of physical aggression and the cost of territory defense,among which calls are one of the most common territorial warning signals.It is common that animals can distinguish intruders and neighbors through territorial calls.In frogs,fishes,birds,and mammals,receivers adjust their behavioral responses according to the calls from strangers and neighbors within or outside their territory.However,previous researches on interspecific recognition and response of territorial calls primarily focused on frogs,fishes,birds,and primates.As one of the highly gregarious mammals,bats mainly rely on acoustic signals to transfer social information in a dark environment.Bats emit complex and diverse territorial calls to compete for their territory.However,it is still unclear whether bats can recognize and respond to interspecific territorial calls.Here,we investigated the recognition and response of interspecific territorial calls among three bat species,i.e.,Great Himalayan leaf-nosed bat(Hipposideros armiger),Pratt's leaf-nosed bat(Hipposideros pratti)and Chinese horseshoe bat(Rhinolophus sinicus).To quantify intraspecific and interspecific recognition behavioral responses and to clarify the interspecific recognition function of territorial calls,we reciprocally broadcast the territorial calls from the sympatric species to each bat species using habituation–dishabituation playbacks.Additionally,we simulated the context of territory defense in male H.armiger toward two sympatric species(H.pratti and R.sinicus)and four different non-living objects(a fur specimen of H.armiger,a bat model,a speaker,and a speaker with playback of H.armiger echolocation calls)to investigate their acoustic responses.The results were as follows:1.All three bat species showed significant behavioral responses when hearing territorial calls from sympatric species.There were no significant differences in nodding and body movements,but there was a significant difference in the number of echolocation calls produced by bats in response to territorial calls from conspecifics and the sympatric heterospecifics,which indicates that bats can recognize territorial calls of the sympatric species.H.armiger and H.pratti significantly reduced the peak frequency,duration and bandwidth of echolocation calls when they responded to the sympatric heterospecifics versus conspecifics,suggesting that bats displayed more intense responses to conspecific vocalizations than heterospecific vocalizations.2.Territorial calls of H.armiger responding to conspecifics and the two sympatric species could be statistically distinguished based on the acoustic parameters of s UFM syllables.The probability of correct classification was significantly higher than a random probability,suggesting there were differences in acoustic responses to different sympatric species.The acoustic responses of H.armiger to conspecifics and H.pratti were similar,but were significantly different toward R.sinicus.The diversity indexs and syllable rate of territorial calls in response to conspecifics and H.pratti were significantly lower than in response to R.sinicus,but the opposite pattern was observed for the proportions of s UFM syllables contained in territorial calls,which might be related to species type,body size and familiarity.3.Territorial calls of H.armiger responding to conspecifics and the four non-living objects could be statistically distinguished based on the acoustic parameters of s UFM syllables.The probability of correct classification was significantly higher than a random probability,which suggests there were differences in acoustic responses to different non-living objects.There were significant differences in the syllable rate and the proportion of s UFM syllables between the conspecific and different non-living objects,which might be related to the shape of the invasive object and whether it is with playback of H.armiger echolocation calls.To sum up,H.armiger,H.pratti and R.sinicus can recognize each other's territorial calls,and their recognition behaviors were the same but the level of responss were different.Additionally,there were significant differences in the territorial calls in H.armiger under different experimental conditions,and H.armiger can adjust its territorial calls in response to different sympatric species or non-living objects.These results add to knowledge of interspecific recognition and response of territorial calls in bats.This study is conducive to the in-depth understanding of animal cognition and species interactions among bats from an acoustic perspective,and provide a theoretical basis for further study on animal communication and protection.