Population Survey And Preliminary Study On The Behavior Of Tibetan Wild Ass In Changtang Area,Tibet

The Tibetan wild ass(Equus kiang)is the largest wild ass in the world.Most of them live on the Qinghai-Tibet Plateau and are considered to be the least studied ungulate in the world.We investigated the population density,diurnal activity rhythm and time budget,vigilance behavior,and group decision-making of Tibetan wild ass.From June to July 2018 and July 2020,we conducted surveys on Tibetan wild ass in the Changtang area of Tibet by line transect sampling,and estimated the density of Tibetan wild ass by Distance software.The results showed that the density of Tibetan wild ass in the Changtang area in 2018 is 0.43±0.11/km²,and in 2020 is 0.48±0.10/km²,which are lower than the density in 2005(0.82±0.20/km²).The daily activity rhythm and time budget of animals are affected by many factors such as light,temperature,predation pressure and so on.We collected the behavioral data of Tibetan wild ass by focal animal sampling,and investigated the daily activity rhythm and time budget of Tibetan wild ass.The results showed that foraging(77.59±1.48%)is the most important behavior in the daytime of Tibetan wild ass,followed by moving(10.09±0.93%),vigilance(9.29±0.81%)and other behaviors(2.87±0.38%).In summer,there are three peaks of foraging for Tibetan wild ass,two peaks of moving and a peak of vigilance.Vigilance is considered as an effective strategy for prey species to detect predators.An individual benefits from living in a group by reducing the time spent being vigilant without affecting the probability of detecting a predator.This phenomenon is called group size effect.We confirmed the group-size effect of Tibetan wild ass by a linear mixed-effects model.We compared the expected value of the collective vigilance with the observed value(Student's t test for paired samples:t₄₂=-3.711,P=0.001).The results showed that Tibetan wild asses scanned the environment at the same time more frequently.We also compared the expected value of the correlation coefficients of individuals with the observed value(Wilcoxon test:N=287,Z=-5.853,P<0.001).The results showed a positive correlation between group members'behaviors,indicating that Tibetan wild asses tend to synchronize their vigilance.In order to benefit from group living,an individual need to adjust its own activities and reach consensus with other group members.This process is called group decision-making.We conducted a preliminary study on the group decision-making of Tibetan wild ass.The results showed that the participation rate of moving-to-vigilance(91.20±3.58%)was significantly higher than foraging-to-moving(65.27±3.63%)and vigilance-to-moving(75.75%±3.82%).We analyzed the influence of group size on group decision-making,and the results showed a negative correlation between group size and the participation rate of decision-making(Spearman's correlation:r=-0.681,P<0.001).In the research on response time,we found that the probability of followers joining the group decision-making depends on the number of individuals who have joined the group decision-making.We investigated the population density,diurnal activity rhythm and time budget of Tibetan wild ass.We confirmed the group size effect and synchronized vigilance of Tibetan wild ass.In addition,we conducted a preliminary study on the decision-making of Tibetan wild ass.The study of the behavior of the Tibetan wild ass is helpful for us to understand how the Tibetan wild ass adapts to the environment of the plateau,and also provides a scientific basis for the protection of this species.