The Social Hierarchy Of Captive Macaca Fascicularis And The Relationship Between Social Hierarchy And Depressive Behaviors

Background:Brain research program has been rising in the world,and China has a greater resource advantage in this field.In addition to having a larger number of clinical patients,we have a wealth of non-human primates(NHPs).China is one of the major providers of NHPs for international researches,among of which the Macaca fascicularis(long-tailed macaques)are farmed and bred on a large scale.The captive monkey group will become the optimal animal model for spontaneous neuropsychiatric disorders.Depressive disorder is a common and harmful mental disease,which imposes heavy economic and psychological burdens on society and family.The work of prevention and treatment for Major depressive disorder(MDD)at currently is not done very well,which is mainly caused by the complex pathogenesis of the disease and the lack of reliable animal model of MDD.At present,the naturally occurring NHPs depression model is considered to be the most ideal animal model of depression and the occurrence ofdepressive behavior is relation to social stress.Social stress is based on the complex social relationships of monkey group,in which the most important one is the social hierarchy.Social relationships are affected by the composition of group and living environment.But the reports on the social rank of captive Macaca fascicularis are rare.Therefore,the systematical study on the social hierarchy of captive Macaca fascicularis group and on the relationship between the social rank and depressive behaviors is not only helpful to improve the preparation of the naturally occurring NHPs depression model,but also useful for researchers and managers to improve the understanding of the social behavior of captive long-tailed macaques.Objective:1)To clarify the social hierarchy of captive long-tailed macaques;2)To explore the factors that affects the social hierarchy of captive monkey group;3)To explore the relationship between the social hierarchy and depressive behaviors.Methods:Firstly,by dynamic acquisition of the aggressive-submissive behaviors between the two members of three long-tailed macaques groups(one old breeding group,one new breeding group and one new non-breeding group)and establishing the matrix relationships in each month to determine thesocial hierarchical characteristics of the old and new groups by the David’s scoring(DS)and linearity H index;Secondly,by analyzing separately the relationship between the individual’s weight,age,body size,productive success and social rank to find out the factors that affects the individual rank order,and by analyzing the effects of the familiarity of members before group formation,and the isolation of alpha male monkey and alpha female monkey from group,on the social hierarchy to clarify whether those factors will affect the social rank;Thirdly,by collection and analysis of behavioral data such as depressive core behavior,living alone,social behavior and so on,to find out the relationship between social hierarchy and depressive monkey,and then based on the social pressure and social support to collection of eating order,the number of attack and being attacked,the winning percentage in conflicts,the common eating time,to preliminary explore the social factors that cause the popular depressive behavior in monkeys with low social rank.Results:The first part: 1)the adult members of new captive long-tailed macaques could form a stable linear social hierarchy within a short of time(2-3 months),and the social structure still existed in the old group;2)individual social rank order of the new breeding group,due to the effects of reproduction,had a longer time to be sure than the new non-breeding group;3)the highest social rank of group was the alpha male monkey,but the betamale monkey’s rank was lower than the alpha female monkey;4)the pups could also form a social hierarchy but the linearity was lower than adult monkeys;5)the relationships between the pups and adult members had a non-linear structure such as a cyclical relationship;6)some of the rank relationships between the pups and their mothers could be reversed as the pups grow up.The second part: 1)the social hierarchy could be affected by the familiarity of members before group formation;2)the relationships between the social rank and age,weight,body size were weak in adult members;3)the social rank of pups was mainly affected by age and had a weaker relationship with their mothers;4)productive success could improve the mothers’ social rank and which would not be affected by the isolation of their infants;5)the alpha monkey had little effects on the social hierarchy of adults,but had a great influence on social rank of pups.The third part: 1)the depressive core behaviors and living alone in low social rank groups were significantly more than high social rank groups;2)the female members of low social rank suffered more social stress and were lack of social support.Conclusion:Like the wild groups,the captive groups of Macaca fascicularis could also form a stable linear social hierarchy.The social ranks of adults and pups were affected by different factors.The female members of low socialrank were easily appeared depressive behaviors,which were the result of more social stress and less social support.