四川省竹巴笼自然保护区矮岩羊的集群特征

2007 年7 ～12 月和2008 年4 ～6 月,采用样线法和定点观察法,在四川省竹巴笼自然保护区对矮岩羊集群行为进行了观察。2007 年观察到34 群共217 只矮岩羊,集群平均为6. 4 ± 4.9 只;2008 年观察到16 群共135只,集群平均为8.4 ± 7.7 只。集群分为雄性群(2007 年:8.8% ;2008 年:6.3% )、雌性群(2007 年:2. 9% ;2008 年:0)、混合群(2007 年:70.6% ;2008 年:81.2% )、母仔群(2007 年:8.8% ;2008 年:12. 5% )和孤羊(2007 年:8.8% ;2008 年:0)5 种类型。在不同季节,5 种集群类型比例都有所变化,差异显著(P <0.01)。集群大小间和集群类型间也有显著或极显著差异,其中2 ～ 10 只的集群在2007 年占73.5%,在2008 年占75.0% ,呈集小群特征。年龄组结构中,成体、亚成体和幼体个体数比为100∶ 26.4∶ 28. 6 (2007 年)和100∶24.7∶ 20. 4 (2008 年)。雌雄性比2007 年为100∶ 55.7,2008 年为100∶ 56.6,年间差异不显著(P > .05)。受集群收益、生物学特征、繁殖周期、资源竞争、生境地形地貌、捕食风险和人类活动等主要因素的影响,矮岩羊在集群类型、集群大小、年龄结构和性比上显示了其生存策略。

Group patterns of dwarf blue sheep (Pseudois schaeferi) in Zhubalong Nature Reserve, Sichuan Province, China

The dwarf blue sheep (Pseudois schaeferi) is an endangered species only inhabiting upper Jinsha River gorge (Zhubalong, south of Batang),Sichuan Province, China. From July to December 2007 and April to June 2008,we investigated group patterns of dwarf blue sheep by using transect censuses and fixed point observations in Zhubalong Nature Reserve. 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 (2007:2.9%, 2008:0),mixed (2007:70.6%, 2008:81.2% ), mother-offspring (2007:8. 8%,2008:12.5% ),and solitary individual (2007:8.8%, 2008:0). These group types varied in proportion seasonally (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. The results indicated that group size was highly 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 were 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 and topography, predation risk, and human disturbance, group patterns of the sheep implied a survival strategy.