Research On The Conflict Resolution Strategies Inside The Society Of Asian Particoloured Bats

Social animals may cooperate to access to resources,such as food.However,unavoidable conflicts over limited resources could arise between individual group members.The game theory stated that the best strategy for conflict resolution is minimizing the energy expenditure.Animals can estimate the competition ability of the opponents by honest signals and select suitable fighting strategy to resolve the conflicts.The creation of dominance hierarchy can also reduce intra-group conflicts.Thus,the research on intra-group conflict resolution strategies can be initiated from three aspects:signal honesty,fighting strategy and dominance hierarchy.In this study,we tested the resolution strategies of intra-group conflicts in Asian particoloured bat(Vespertilio sinensis).During agonistic encounters,the opponents often exchange information about their resource-holding potential or aggressive intent via aggressive signals.We tested whether aggressive calls of Asian particoloured bats were the honest signals of resource-holding potential(RHP,the body size and the quality)of the caller,through analyzing the relationships between body size indexs,quality indexes and winning percentage and aggressive vocalizations.At the syllable level,there were significant positive relationships between the duration of various syllables and forearm length,bite force and winning percentage.In addition,frequencyrelated syllable parameters,such as peak frequency,minimum frequency,maximum frequency and bandwidth,were negatively correlated with immune response and winning percentage.At the call level,heavier bats that produced calls with shorter mean inter-syllable silences had higher winning percentage and healthier bats produced calls with lower maximum frequency.There was a significant positive relationship between immune response and vocal complexity,but no significant relationship was found between winning percentage and vocal complexity.These results suggested that aggressive calls in Asian particoloured bats may be honest signals of body size and quality during the antagonistic interactions.Residents frequently produced aggressive vocalizations when they were pushed by an intruder for a better roosting site.The intruders would then either continue pushing or stop.Thus,we tested whether aggressive vocalizations of Asian particoloured bats encoded reliable information about the aggressive intent,through analyzing the difference of aggressive vocalizations between stopping push encounters and continuing to push encounters.Our results showed that the number of noisy/tonal syllables of the disturbed bats met the three criteria used to define aggressive intent.First,the number of tonal syllables and the ratio of tonal syllables were significantly greater in continuing to push encounters,and the number of noisy syllables and the ratio of noisy syllables were significantly greater in stopping push encounters(context criterion).Second,skin temperature related to emotional arousal during aggressive interaction,generally increased after stopping push encounters but was unchanged or decreased after continuing to push encounters(predictive criterion).Finally,bats preferentially selected stimuli with more tonal syllables,and they spent more time in approaching more noisy syllables stimuli in two-choice playback experiments(response criterion).Thus,we propose that the number of noisy/tonal syllables within aggressive vocalizations of Asian particoloured bats function to signal aggressive intent.We examined the assessment models of fighting strategies in Asian particoloured bats,through analyzing both randomly and size-matched contests.Our results showed that forearm length was the best metric of RHP in both randomly and size-matched contests(had the lowest Akaike information criterion(AIC)scores,within 2 ?AIC,appeared most frequently in the best-supported models).Forearm length difference between opponents has a significant negative relationship with contest duration in randomly matched contests.Nevertheless,there was no significant relationship between average forearm length of opponents and contest duration.Therefore,the assessment strategy used by Asian particoloured bats during aggressive interactions was mutual assessment.Through calculating corrected Kendall's K',the number of circular triads(d')and Landau's h',we found that the dominance hierarchy of Asian particoloured bats was linear hierarchy.The forearm length was positively correlated with dominance hierarchy,indicting that individual differences,such as body size,could affect formation of dominance hierarchies.Bats with longer forearms had higher dominance ranks.Additionally,in the experimental group with prior residents,the dominance ranks of prior residents were significantly higher than nonprior residents.In the control group without prior residents,there was no significant difference in dominance ranks between individuals from different cages.These results indicated that social dynamics,such as prior residence,could also affect the formation of dominance hierarchies.In conclusion:(1)aggressive vocalizations in Asian particoloured bats encoded honest signals of body size,quality and aggressive intent;(2)Asian particoloured bats used mutual assessment to settle conflict;(3)dominance hierarchies of Asian particoloured bats were determined by both individual differences(body size)and social dynamics(prior residence).The reliability of acoustic communication in bats will provide theory gist for an indepth understanding of the function and evolution of social calls in bats.Asian particoloured bats could resolve intra-group conflicts effectively based on several strategies,for instance,honest signals,assessment of fighting ability and formation of dominance hierarchies,in order to reduce energy consumption and maintain community stability.