Research On The Resolution Strategies Of Territorial Conflict And Evolutionary Drivers Of Territorial Calls Of Male Great Himalayan Leaf-nosed Bats

Competition for limited resources is common in most social animals.This competition can involve physical fighting that involves injury risk and energy expenditure,and even death,which ultimately affects the survival and reproductive fitness of individuals and populations.However,animals often use fight assessment strategies and communication signals that encode information about fighting ability to resolve conflicts,thereby avoiding escalation of fighting and reducing the cost of fighting.Uncovering the conflict resolution strategies,information content contained in communication signals and the evolution of communication signals is a hot topic in the field of animal behavior and evolutionary biology.It will also provide a scientific basis for a deeper understanding of human conflict behavior and the origin and evolution of human language.Chiropterans are commonly known as bats.Conflict between bats frequently occurs when crucial resources,such as food,mating opportunities or roosting territories,are limited.Bats commonly produce complex and diverse territorial calls during conflict.However,in bats,studies on fighting strategies,information content encoded in territorial calls and evolutionary mechanism of territorial calls are still scarce.Here,I recorded and analyzed agonistic interactions and territorial calls of male Great Himalayan leaf-nosed bats(Hipposideros armiger),and then combined body size,dominance rank,climatic,geographical,genetic factors and playback experiments,to determine the fighting strategies,information content encoded in territorial calls and evolutionary mechanism of territorial calls.Animals often use fighting strategies to resolve conflicts during a territorial conflict.However,so far,there have been no reports on the fighting strategies of bats occupying a unique ecological niche in the night sky,which is not conducive to understanding the conflict resolution process of nocturnal mammals.By analyzing111 agonistic interactions of 222 males,we found that there were 5 main behavioral displays including ear movements,head raise/turn,unfolding wings,boxing and wrestling.In physical contests,contest duration was unrelated to the winner's mass but was positively correlated with loser's body mass.This indicated that males make decisions based on their own RHP(self-assessment: the energetic war of attrition model)rather than on RHP of their opponent(mutual assessment).Humans and even many animal species convey information about their individual identity and emotional state with vocal signals.So far,in bats,studies on individual recognition of territorial calls and vocalizations signalling the emotional state are still scace.By comparing differences in acoustic parameters of bent upward frequency modulation(b UFM)calls between low and high aggression intensity,and among individuals,we found that at high aggression intensities,males decreased the minimum frequency of b UFM calls and increased the frequency bandwidth.Males also transferred energy from the second harmonic to the frst harmonic as the threat escalated.The b UFM calls encoded discriminable signatures,and males could discriminate among individuals based on these b UFM calls.These results indicated that bats can modify the syllable in systematic ways to encode information about both individual identity and emotional state,and can detect minor modification of b UFM calls.Vocal performance trade-off is an ability of an animal to excel in the performance of a signal characterized by a trade-off between bandwidth and syllable repetition rate.It is unknown whether bats' social calls show a vocal performance trade-off.By analyzing the acoustic parameters of 232 b UFM calls produced by 64 different males,we found that b UFM calls exhibited a negative correlation between syllable repetition rate and frequency bandwidth,indicating a vocal performance trade-off.Vocal deviation was significantly negatively related to body mass,indicating b UFM calls contained information about individual quality.Multiple messages hypothesis proposes that diferent signals provide information about diferent aspects of the signaller's condition,and thus allows receivers to more comprehensively assess signallers' quality.Most studies on the multiple messages hypothesis in the acoustic domain have focused on vocalizations consisting of diferent element types;whether single element types themselves can convey diferent types of information is not well studied,especially in the context of territorial conficts.By analyzing the acoustic parameters of 224 stepped upward frequency modulation(s UFM)calls produced by 16 bats and analyzing a total of 1657 agonistic interactions from 16 bats to determine the dominance rank for each bat,we found that s UFM calls encoded multiple types of information: body mass,dominance rank and individual identity.Males have the ability to utilize this vocal individual signature to discriminate between vocalizing males.These results indicated that syllables in monosyllabic vocalizations can convey multiple types of information and bats can detect these multiple information.Geographical variation in acoustic signals is common in many animal species.Although studies have shown that there are geographical variation in bat communication calls,there is a lack of more comprehensive research on the evolutionary causes of geographical variation of communication calls and the lack of the impact of differences between communication calls on bat populations.By analyzing the acoustic parameters of b UFM calls from nine colonies at a large geographical scale,we found that neither climatic differences,morphological differences,geographical distances nor genetic distances between colonies explained the observed acoustic variation between colonies.A playback experiment indicated that males have the ability to discriminate between territorial calls of its own colony and those of a foreign colony.These results indicated that accurate individual recognition may drive the large amount of variation in b UFM calls of H.armiger and thus weaken the influences of ecological selection and drift.In summary,to our knowledge,this is the first comprehensive research on fighting strategies and vocal performance trade-off of social calls in Chiropterans.It is also the first study on the influence of geographical variation in bat communication calls on individual recognition.Our results will be important to understand the adaptive evolution of bat communication calls and the sensory drive of speciation.