Study On Population Ecology Of Dwarf Blue Sheep

As an endangered species,dwarf blue sheep was listed in ClassⅡof the National Key Protected Animals in China.The sheep is an endemic species only inhabiting in Jinsha River gorge at the southeastern Tibetan Plateau(mainly in Zhubalong,south of Batang County).We conducted an investigation into population ecology of dwarf blue sheep in Sichuan Zhubalong Nature Reserve in August 2006 and July-December 2007 and March-June 2008.We described and studied the ethogram,PAE behavior coding,activity rhythms,time budget,group pattern of dwarf blue sheep and seasonal change in habitat selection.The main results were summarized as follows:We established a behavioral functional classification and coding system for the behavior of dwarf blue sheep.'Posture','Act' and 'Environment' were coded with PAE via distinguish basic unit of animal behavior and analyze behavioral hierarchy.11 postures,75 acts and 92 behaviors of dwarf blue sheep were recorded and classified as follows:feeding,ruminating,resting,moving, urinating/defecating,thermo-regulating,rutting and estrous behavior,mating,parental behavior, communication behavior,aggregation behavior and miscellaneous behavior.Frequency and seasonal occurrence of different individual behavior within sex-age classes were also recorded in PAE system.Population individuals of dwarf blue sheep were divided into 4 sex-age classes according to their ages and sexes.Activities of the sheep such as feeding,lying,moving,standing and other behavior,were recorded by using a modified version of traditional focal and instantaneous sampling. We used nonparametric Mann-Whitney U and Kruskal-Wallis H tests to compare differences in the time budgets among different sex-age classes and different seasons.The sheep spent the majority of their time feeding and lying,44.56±2.72%and 25.54±3.19%of all activities respectively.The remnant time was devoted to other three activities,such as standing(15.15±0.60%),moving(11.39±0.55%) and other behaviors(3.40±0.31%).The percentage of daytime spent in feeding reached its lowest level(40.80%) in August and highest level(49.66%) in December.In contrast,lying reached its highest level(29.35%) in August and lowest level(18.85%) in December.Dwarf blue sheep had two daily peaks of feeding(early morning and late afternoon) and one peak of lying in midday during spring,autumn and winter,but also showed three peaks of feeding(early morning, midday and late afternoon) and two peaks of lying(at 10:00-11:30 and 13:00-14:30) during summer. Feeding remained at relatively higher levels(47.01%) and lying kept at relatively lower levels (21.95%) in winter,and contrarily in summer.No significant differences in general activity budgets between adult males and females and between adults and subadults were found,but adult males were found to spend more time in other behaviors than adult females and subadults.Kids spent significant more time in lying and less time in feeding and standing than did other sex-age classes,but no significant differences in daytime spent moving among all sex-age classes.We investigated group patterns of dwarf blue sheep by using methods of transect censuses and fixed point observations.We observed 34 groups consisting of 217 individuals with a mean group size of 6.4±4.9 in 2007 and 16 groups comprising 135 individuals with a mean group size of 8.4±7.7 in 2008.Sheep groups can be classified into five types:male only(2007:8.8%of total groups,2008:6.3%),female only(2.9%,0),mixed(70.6%,81.2%),mother-offspring(8.8%,12.5%), and solitary individual(8.8%,0).These group types varied seasonally in proportion(P＜0.01).These types also differed in distribution(P＜0.01) and in size(P＜0.01).Groups of 2-10 individuals were predominant(73.5%of all groups in 2007 and 75.0%in 2008).We collected population data from several recent articles(1997,1998,2000,2006) to analyze mean group size and sex ratio dynamics using the ANOVA technique.The results indicated that group size was very variable(P＜0.05) and the mean group size was significantly larger in 2007(P＜0.05) and in 2008(P＜0.01) than in 2000. The adult:juvenile:lamb ratio was 100:26.4:28.6 in 2007 and 100:24.7:20.4 in 2008.The female:male ratio(100:55.7 in 2007 and 100:56.6 in 2008) remained stable(P＞0.05).Group patterns of the sheep can be influenced by benefits in group living,biological characteristics, breeding cycle,competition for resources,habitat type or topography,predation risk,and human disturbance,group patterns of the sheep implied a survival strategy.We set up 10 line transects to investigate habitat selection of dwarf blue sheep and the Chi-Square Test and Mann-Whitey U Test were used to analyze the raw data.The sheep preferred areas during autumn-winter with the following attributes:well-sheltered from wind,lithoid or partially lithoid substrates,10%-40%shrub canopy cover,5 or more shrub species,tall shrubs(＞100 cm),6 or more herbaceous species,short(＜20 cm) or tall(＞40 cm) grasses,cliffy(＞60°) and sunny slope,low(＜30%) or high(＞60%) levels of concealment,moderate distance to water source(＞500 m),short distance to bare rock(＜2 m),moderate distance to forest edge(1000-1500 m),low altitude (＜2800 m),moderate distance to human disturbance(500-1000 m) and animal disturbance(80-150 m).While the sheep preferred areas during spring-summer with the following attributes:concave or convex slope form,well or worse -sheltered from wind,lithoid or partially lithoid substrates. 10%-40%shrub canopy cover,biggish herbaceous canopy(＞30%),4-5 shrub species,tall shrubs (＞100 cm),4-5 herbaceous species,short(＜20 cm) or tall grasses(＞40 cm),steep(＞60°) and sunny slope,moderate distance to water source(＞500 m),long distance to animal disturbance(＞80 m), long distance to human disturbance(＞500 m),high(＞60%) levels of concealment,short distance to bare rock(＜2 m),short distance to forest edge(＜1000 m),medium altitude(＞2600 m).The results of factor analysis indicated that autumn-winter habitat selection was mainly influenced by distance to human disturbance,altitude,distance to forest edge,distance to water source,shrub height,level of concealment,wind speed and distance to animal disturbance.While spring-summer habitat selection was mainly influenced by distance to human disturbance,altitude,distance to forest edge. herbaceous height,herbaceous canopy,slope gradient,slope form.