Abstract: The characteristics of summer den habitats of the Tibetan fox (Vulpes ferrilata) were studied in Shiqu County in western Sichuan province during July 2001. Over 230 km were sampled by line transects (totally 40 km , ranging between 4 200 and 4 500 m of altitude) . For each fox den , 7 ecological factors (water distance , den direction , slope direction , slope degree , position in the slope , vegetation type and small mammal pika or rodents den number) were recorded in 5 ×5 square meters centred on the den. 91 Tibetan fox dens were found. Among them 54 dens were fully described and classified by a principal component analysis (PCA) followed by a cluster analysis (complete linkage hierarchical ascendent classification on euclidian distance) . The first four factors of the PCA represent 85 % of the total variance. Water distance , slope degree and the position in the slope are the three most important variables contributing to the first factor. This factor represents 42.8 % of the total variance. Small mammal den number and vegetation type are also important in the latter 3 factors. In the cluster analysis , dens were grouped into three main groups (A: 26 dens , B : 22 dens , and D: 6 dens) . Group A is more coincident than group B , and both these two groups comprised the group C. Group C is quite different from group D , water distance is the main reason coursing the difference. The water distance in group C is no more than 500 m , but longer than 800 m in group D. Tibetan fox dens are mainly in middle (6815 % of 54 dens) and sunny or half sunny slope (92.6 %) , lower position in the slope (87.04 %) and with moderate water distance to den ( < 500 m) (87.04 %) . The directions of the fox dens range from 35°to 360°(88.9 %) . Most dens were located in grasslands(96.3 %) with moderate slope (68.52 % are between 5°and 25°) . In addition , small mammal dens were always found in the 5 m ×5 m sample squares , at a various number. It is suggested that the relationship between small mammal dens and fox dens distribution should be studied in the future.

Key words: Tibetan fox, Den, Principal components analysis, Cluster analysis

摘要： 通过对四川石渠地区夏季藏狐洞穴生境选择的研究, 以水源距离、洞口朝向、坡向、坡度、坡位、植被类型及鼠兔和鼠类洞穴等7 项指标为变量, 运用主成分分析和聚类分析相结合的方法对收集到的54 个藏狐洞穴样本进行了分析。主成分分析在4 个主成分下达到85 %的显著性。在第一主成分中水源距离、坡度和坡位是重要的影响变量, 在另外3 个主成分中鼠类洞穴数量以及植被类型两变量也非常重要。聚类分析显示, 54 个洞穴样本在3 个水平上聚成5 类。藏狐易于选择草甸地带, 中缓坡和低坡位, 坡向多为阳坡或半阳坡, 水源距离小于500 m的地方筑巢, 其穴口朝向多位于135°～ 360°之间。此外, 鼠兔和鼠类洞穴在藏狐洞穴样方内的出现, 但数量变异较大, 揭示小型哺乳动物和藏狐之间可能存在着复杂的相互关系。

关键词: 藏狐, 巢穴, 主成分分析, 聚类分析