Studies On The Characteristics And Function Of Multimodal Communication Signals In Territory Conflicts Of Hipposideros Armiger

Multimodal communication involves the use of signals and cues across two or more sensory modalities.Multimodal communication is especially important for courtship,predation and territory defense.In the field of multimodal communication,an important question is why animals display multimodal signals.Based on this,studies on the characteristics and functions of mammalian multimodal communication have been one of the frontier and popular issues in the field of behavioral ecology and animal communication,which is helpful to reveal the origin and evolution of human language.Bats comprise the second largest order of mammals.Most bats are highly gregarious,which usually roost in caves.To maintain the stability of the social group,bats communicate their own attributes and external events to other individuals through multimodal signals such as auditory,olfactory,visual,and tactile signals.However,previous studies mainly focused on characteristics and function of multimodal signals in the feeding and courtship contexts rather than roost territory.There were no studies on the dynamic response of receivers to the interaction of multimodal signals.In this case,this will lead to understand unilaterally and imperfectly the design and function of multimodal signals.The Great Himalayan leaf-nosed bat,Hipposideros armiger,emitted two types of calls in two roost territorial contexts,and protruded the forehead gland,which indicated the presence of multimodal signals.Here,bent upward frequency modulation(b UFM)calls were emitted during agonistic interactions between two bats that have perched close to each other and stepped upward frequency modulation(s UFM)calls were emitted by a roosting individual when a free-flying bat approached.In this study,we selected the Great Himalayan leaf-nosed bat as the research object.We recorded and analyzed territorial calls and territorial behaviors,collected and identified the volatile chemical composition in the forehead gland secretions,and combined the behavioral and physiological playback experiments to reveal the characteristics and functions of each modal signal as well as the role and relative importance of multimodal signals in conflict resolution.In this study,we recorded the two types of calls,and analyzed the difference in acoustic parameters of these two types of territorial calls.Then,we conducted two-choice experiments to test the function of these two types of territorial calls.Our results showed that there were significant differences in acoustic parameters between b UFM calls and s UFM calls(MANOVA:Wilk's lambda=0.278,df=2,22,P<0.0001).Moreover,the bats avoided the location of b UFM call playbacks independent of the simultaneous playback of echolocation calls,silence or s UFM calls(Exact binomial tests:all P<0.05).The bats also avoided approaching the side of the flight room where s UFM calls were broadcast when also presented with playbacks of echolocation calls(P<0.05),but not when simultaneously presented with silence(P>0.05).The results suggest that b UFM calls may serve the function of territorial defense,while s UFM calls may convey information of the sender's emotional state.Therefore,our results imply that the two types of calls have different functions depending on behavioral context.In this study,we detected the chemical composition of forehead gland secretions from 7 males.Then,we ran two sets of behavioral tests to evaluate the potential function of these secretions.Our results showed that forehead gland secretions contained 16 categories of compounds(84 volatile compounds).In particular we found significant correlations between alkane compounds that have previously been shown to function in individual recognition,and aldehyde and ketone compounds that have been shown to function in threat displays(P<0.05).These results suggested that the functions of individual discrimination and mutual threat between two rivals may be coupled during agonistic interactions in H.armiger.Moreover,the concentrations of compounds(ANOSIM:Global R=0.183,P=0.008)and their categories(ANOSIM:Global R=0.196,P=0.004)differed significantly among individuals.These results suggested that the chemical compounds of gland secretions convey information on individual identity.All bats could discriminate individual differences in odors of forehead gland secretions between different individuals(Paired t test:t₁₁=8.131,P<0.001).During agonistic interactions,paired males that were incapable of gland protrusion showed more physical contact(Pearson chi-square test:?²=6.144,df=1,P=0.013)and longer contest duration(ANOVA:F_2,57=4.64;P=0.012)compared to pairs in which both males could protrude the gland.In trials where only one male could protrude the gland,males with gland protrusion were more likely to win in contests(Binomial test:P=0.001).These results suggested that chemical signals of H.armiger functioned as a highly effective threat,which could prevent contest escalation and decrease the conflict-related costs.Finally,we monitored the change of the heart rate by real-time,and compared the difference in the duration of elevated heart rate and magnitude of change in heart rate when we playback acoustic(b UFM calls),olfactory and combined stimuli.Our results showed that the duration of elevated heart rate and magnitude of change in heart rate showed a significant increase when acoustic or multimodal stimuli were present,compared to olfactory stimuli(P<0.05).However,there were no significant differences in the duration of elevated heart rate and magnitude of change in heart rate between multimodal and acoustic stimuli(P>0.05).Our results showed a dominance of the acoustic modality,suggesting that acoustic and olfactory signals in H.armiger might be non-redundant.Together,this study clearly clarified the characteristics and function of multimodal communication signals in territory conflicts of H.armiger from the levels of behavior and physiology,based on the function of acoustic communication and chemical communication.This is the first study to clarify that chemical signals serve the function of threat in bats,and to reveal that multimodal signals might be non-redundant in bats,which is important to elucidate the evolution of multimodal communication.Consequently,the study will show the innovative achievements in multimodal communication,help understand the origin and evolution of human language,and thus can provide scientific basis for bats'training,management and their diversity conservation from the aspects of acoustics and behaviour.