Effects Of Human Disturbance On The Blue Sheep(Pseudois Nayaur)and Its Skull Morphology On The Central Tibetan Plateau

The Tibetan subspecies of blue sheep is widely distributed in Tibet and,as it is a prey of many large carnivores,plays an important role in the stability of the plateau ecosystem.However,there are no reports on the number and distribution of blue sheep populations in central Tibet,and the geographical boundaries of Tibetan subspecies are unclear.With population growth and economic development,human-wildlife conflicts are gradually increasing.Net fencing dividing pastures exacerbates blue sheep habitat fragmentation and causes death of sheep.Livestock grazing increases risk of interspecies disease transmission.The lack of population monitoring data for blue sheep makes it difficult to develop management and conservation policies.Therefore,this paper investigates the population distribution,community structure and life table of blue sheep in central Tibet,analyzes the factors influencing the habitat of blue sheep,evaluates the survival status,and provides basic ecological data for formulating wildlife management policies.At the same time,the morphological features of the blue sheep skull were measured to provide morphological evidence for distinguishing and validating the Tibetan and Sichuan subspecies.To this end,a preliminary survey of blue sheep populations in a total of 18 counties in central Tibet was conducted in four quarters,from December 2017 to August 2019,in winter and summer,collecting data such as population size,sex ratio and juvenile ratio,as well as skull and horn samples of male blue sheep dead individuals.Based on the occupancy model approach to predict the distribution of blue sheep,a static life table was made by synthesizing the sheep horn data,and the main anthropogenic disturbance factors and the degree of disturbance to blue sheep were discussed.Comparison and clustering analysis of skull morphology of the Tibetan and Sichuan subspecies of the blue sheep had been done.The following results were obtained:1 Recent expeditions identified 462-464 individuals from 18 groups in 9 counties in central Tibet.The age structure of the population was 19.05% subadults,57.14% males and 23.81% seniors.Based on other evidence and projections,blue sheep are likely to be present in four more counties.2 The estimation of detection rate was 72.73%(SE=9.16),and among those areas where blue sheep were not detected,it is believed that blue sheep are present in Doilungdeqen and Gamba.In Lhunzhub and Damxung,it is likely that blue sheep populations move in and give birth in the spring,presumably the habitat selection of blue sheep in this season is different from that in winter and summer.Of all the human activities,grazing and net fencing has the greatest impact to habitat occupancy,and the significance of human activities exceeds the impact of water and habitat.It is believed that populations in the study area are more severely disturbed by human,so conservation and management policies need to be developed and improved in a timely manner.3 The life table of blue sheep was established based on the horns of 21 male blue sheep,and the analysis found that there was no significant correlation between horn base circumference and age and habitat(P>0.05),and horn length and average annual horn growth show extremely significant differences at different ages(P<0.001),and extremely significant differences(P<0.01)across habitats.Indicates that horn length and annual growth can reflect habitat quality and survival to some extent.Compared to the populations in Helan Mountain and Qinghai Province,the survival status and habitat quality of the populations in central Tibet are considered poor.4 After measuring the morphological characteristics of skulls from 16 blue sheep,the results of single skull morphology showed that compared with the Sichuan subspecies,the Tibetan subspecies had extremely significantly wider tear bones(t=-3.522,df=23,P=0.002),extremely significantly wider temporal bones(t=14.757,df=25,P < 0.001),significantly longer frontal bones(t=-2.502,df=12,P=0.028),extremely significantly longer occipital bones(t=-9.203,df=8,P < 0.001),and extremely significantly longer horn base lengths(t=-9.203,df=8,P<0.001).Based on skull morphology the clustering analysis found that the Sichuan subspecies were clustered separately into one,while the branching between the Tibetan subspecies in different regions was unclear,indicating that skull morphology could effectively distinguish the Tibetan and Sichuan subspecies.Based on the above results,it is considered that large amount blue sheep are widely distributed in central Tibet,but are affected by human activities significantly.Therefore,while continuing to survey the distribution of populations and geographical boundaries of subspecies in central Tibet,targeted policies on grazing and net fencing should also be developed to enhance the management and protection of wildlife in this region.