| Primates adapt to different social and natural environments through various social organizations to maintain the survival and reproduction of the population.Multi-level society is extremely rare in non-human primates which is the most complex social organization model in non-human primates.The all-male unit is an important part of the multi-level society organization,but there is still a lack of research on the regulation mechanism of the number and spatial and temporal distribution of the all-male unit,which is not conducive to the understanding of the behavior strategy of the all-male unit in the multi-level social system.At present,there have been studies on the hierarchy,association,and reproductive strategies of the all-male unit in multi-level society.However previous studies on the all-male unit have come from the monkeys in artificial feeding states,which eliminates the influence of seasonal changes in food on the all-male unit in the natural environment.It is not enough to objectively understand the adaptation strategy of the number and spatial and temporal distribution of all-male unit in multi-level society systems.From November 2021 to November 2022,a group of wild black and white snub-nosed monkeys in Lasha Mountain Yunling Provincial Nature Reserve Lanping County Nujiang Prefecture Yunnan Province was selected as the research object in this study.The monkey group has achieved non-feeding habituation through long-term tracking and can achieve close observation and data collection.By collecting the data of the number and spatial distance of all-male individuals and the spatial relationship of breeding groups to explore the effects of the number of the female in breeding groups,food resources,and reproductive pressure on the number and spatial distribution of all-male unit of black-and-white snub-nosed monkeys.The study intends to solve the following three scientific problems:1)The reasons and regulatory factors of the number change of the all-male unit and verify the female group-size hypothesis;2)How does food resources regulate the relationship between the all-male unit and the influence of food resources changes in different seasons on the spatial distance of the all-male unit;3)How does reproductive pressure regulate the spatial distance between individuals in the all-male unit the spatial distance between the all-male unit and the breeding group,and the behavioral adaptation significance of the spatial distribution of all-male unit under different reproductive pressures.Research time and data collection methods.The black-and-white snub-nosed monkeys were tracked in the field for 393 days.Focal animal and instantaneous sampling and Instantaneous and scan sampling were used to collect data on the inter-individual distance,the distribution of the all-male unit and the spatial distance between the all-male unit and the surrounding breeding group.All-occurrence recording was used to collect the number changes and member composition of the all-male unit and the breeding group,as well as the conflict behavior data between the all-male unit and the breeding group.According to the seasonal variation of major food availability,the food scarcity period(December 2021-February 2022)and the food rich period(September-November 2022)were divided;according to the breeding season of the monkey group,the breeding period(June-August 2022)and non-breeding period(March-May 2022)were divided.The differences in the distance between the all-male unit and the breeding group were compared during different periods,including the breeding period,non-breeding period,food scarcity period,and food rich period.Changes in number of the all-male unit of the black and white snub-nosed monkey is regulated by the number of females in the breeding group.The more the number of females in the breeding group,the more the number of individuals in the all-male unit,which is consistent with the female group-size hypothesis.The total number of all-male unit in the Lasha Mountains remained at 55-65 throughout the year.The aggregation and separation behaviors of the all-male unit occurred 4 times each during the study.When there were breeding groups in the newly formed community all-male unit were more likely to occur(χ~2=20.80,df=2,P<0.001).The number of individuals in the all-male unit was affected by the number of females in the breeding group(r=0.87,n=23,P<0.001).This is consistent with the conclusion that the number of primate males is affected by the number of females,indicating that the all-male unit of wild black-and-white snub-nosed monkeys will stay in more communities of potential mating partners,which is conducive to the increase of reproductive opportunities for individuals in the all-male unit.Food pressure regulates the spatial distance of the all-male unit and the spatial distribution diameter of the all-male unit.The spatial distance between the all-male unit and the adult group of black and white snub-nosed monkeys was shortened during the period of food scarcity(individual:2.45 m vs 5.14 m,Z=8.06,P<0.001;Adult:4.57 m vs 6.27 m,Z=3.43,P<0.001).In addition,the distribution diameter of the all-male unit was also smaller during the food scarcity period(16.66 m vs 27.76 m,Z=5.41,P<0.001)indicating that food resources played an important role in regulating the stability of the all-male unit.The individual distance is large and the all-male unit is widely distributed which is conducive to reducing competition and enabling each member to obtain more high-quality food but will lead to a decrease in the intensity of inter-individual contact during the food-rich period.The individual takes the highly available Usnea as the main food and its competitive pressure are reduced.If the distance and distribution diameter is shortened,the energy used to alert the surrounding environment can be reduced,and the energy and time can be saved for feeding to improve the survival income,and survive in the harsh forest environment in the wild during the period of food scarcity.Reproductive pressure regulates the spatial distance between the all-male unit and the reproductive group the spatial distance of the all-male unit and the distribution diameter of the all-male unit.First,the all-male unit of black and white snub-nosed monkeys was close to the breeding group during the breeding period and the distance between the all-male unit and the breeding group during the breeding period was smaller than that during the non-breeding period(75.06 m vs 110.40 m,Z=7.67,P<0.001).Secondly,the spatial distance between the all-male unit individuals and the adult individuals was closer in the breeding period(individual:3.28 m vs 6.07 m,Z=7.25,P<0.001;adult:5.15 m vs 9.88 m,Z=5.44,P<0.001).Finally,the spatial distribution diameter of all-male unit individuals was larger than that of the non-breeding period(30.04 m vs 25.58 m,Z=2.07,P=0.04)during the breeding period.In addition,the reproductive competition pressure between male was high and one young male was found to die in conflict with the resident male of the reproductive unit during the study.Therefore,the maintenance of the all-male unit is affected by reproductive resources The breeding period is close to the breeding group and the distribution diameter becomes larger increasing the opportunity to obtain reproduction but the group cohesion decreases;the decrease of inter-individual distance may help to strengthen the group defense against the joint attack of the breeding group.The all-male unit of black-and-white snub-nosed monkeys balances the search for reproductive opportunities(unit outbreeding and unit replacement)and safety(joint attack by the resident male).In summary,we took the all-male unit of wild black-and-white snub-nosed monkeys as the research object,and found that the number of all-male unit of black-and-white snub-nosed monkeys was affected by the number of females in the breeding group and the number of females in the breeding group regulated the stability of the all-male unit.Seasonal changes in food resources affect the spatial distribution of the all-male unit and the spatial distance between individuals and food pressure regulates the stability of the all-male unit.Reproductive pressure affects the spatial distance and distribution of the all-male unit,as well as the distance between the all-male unit and the breeding group.Reproductive pressure regulates the stability of the all-male unit.In conclusion,the all-male unit of black-and-white snub-nosed monkeys under the multi-level society system is regulated by the number of females,seasonal changes in food,and reproductive pressure.The results of the study increase the understanding of the stable maintenance of the all-male unit of black-and-white snub-nosed monkeys under the multi-level society system and help to improve the relevant theories of the maintenance of the stability of primate social organizations. |
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