| The Tibetan fox distributed in Qinghai-Tibet plateau with elevation higher than 3500 m, and prefer broad alpine steppe and meadow areas. Tibetan fox prey mainly on Plateau pika and alpine rodents, which is necessary to maintain grassland quality and keep balance of alpine ecosystem. For a long time, the biological information of Tibetan fox is scarce and little is known about this species. Therefore, research works on fundamental ecology about Tibetan fox is helpful to understand the living pattern adapted by this species in extreme environment, and provide theorietical basis for specis conservation and habitat enhancement.We captured 5 Tibetan foxes ( 4 M, 1 F ) in Gouli township, Dulan county, Qinghai Province in April 2006, September-October 2006, March-May 2007, September-October 2007 and March-April 2008. Radio telemetry technique was used to locate all collared foxes, and the behavior happened at each location was recorded. The temporal and spatial distribution characteristics of the diurnal behavior of Tibetan fox were analyzed, and the relationship between activity index and habitat variables was studied by regression; Based on locations, the home range and home range core of Tibetan fox were estimated through extensions of GIS software; Multi-linear regression model was set to explore the relationship between the probability of utilization distribution and environmental variable attributes; Habitat quality was evaluated according to animal preference (or avoidance) to certain habitat, and the spatial carrying capacity was calculated for Tibetan fox in suitable habitat; We also sepetated fox home range into different biological function areas, studied the denning habitat selection of Tibetan fox, analyzed the food habits of Tibetan fox and provide biological information of some species sympatric with Tibetan fox.1. Diurnal activity characteristics: Tibetan fox moves mainly at dawn and dusk (x~2 test, P < 0.05 ) , and there is significant seasonal difference in behavior rhythm ( Wilcoxon Signed Ranks Test, Z =-2.366, P = 0.018 ) . The fox activity index in warm season ((x|-) =0.60, SD = 0.14) is higher than that in cold season ((x|-)= 0.49, SD = 0.15) . In both warm and cold season, foxes were more active at 8:00-12:00 and 16:00-20:00 and less active at other periods. The spatial distributon of fox activities are influenced by topographic factors. There is minus correlation between fox activity index and slope attributes (B = -0.099), and the activity index is positively correlated with pika density (B - 0.022) . The interaction between pika density and slope affects fox activity index positively (B = 0.073). Foxes will be less active with the increasing of elevation (B = -0.023) .2. The diurnal behavior rhythm of Tibetan fox pups: The diurnal behavior rhythm of young pups was not normally distributed (χ~2 test, P < 0.05) , and mainly composed by resting (Time percentage is 55.1 %; Frequency percentage is 45.0 %) , hunting (Time percentage is 20.0 %; Frequency percentage is 19.0 %) and gamboling behavior (Time percentage is 16.7 %; Frequency percentage is 39.0 %) . The pups were active at dawn and dusk; they are active at 8:00-9:00 and 15:00-16:00, and less active 13:00-14:00. Young foxes were much active when adult fox appeared(χ~2 test, P < 0.05), and their behavior were mainly composed by gamboling (Time percentage is 50.0 %; Frequency percentage is 54.7 %) and running behavior (Time percentage is 16.2 %; Frequency percentage is 18.6 %) .3. Fixed kernel, Harmonic mean and Minimum convex polygon estimators were used to calculate the home range of Tibetan fox, and the home range core was determined by Area of independent method (AIM). Fixed kernel estimator: In warm season, the home range size of Tibetan fox was 2.81 km~2-3.29 km~2 ((?) = 2.95 km~2, SD = 0.22) , the home range core ( (?) = 0.88 km~2, SD = 0.37) take a percentage of 17.3 %-38.1 % of the total home range; in cold season, the home range size is 1.99 km(?)-3.70 km(?) ((?) = 3.36 km~2, SD = 1.07), and the home range core size ((?)= 1.00 km~2, SD = 0.49) is 15.7 %-36.3 % ((?) = 29.9%, SD = 9.5%) of the total home range. Harmonic mean estimator: In warm season, the home range size is 0.87 km~2-2.89 km~2 ((?) = 1.67 km~2, SD= 1.08), and the home range core ((?) = 0.33 km~2, SD = 0.14) take a percentage of 16.6 %-34.5 % ((?) =22.7 %, SD = 10.2 %); In cold season, the home range size of Tibetan fox is 1.33 km~2-4.99 km~2 ((?) = 3.09 km~2, SD = 1.68) , and the home range core size is 0.29 km~2-1.11 km~2 ((?)= 0.64 km~2, SD = 0.40)。There is overlap between home range and core area of different fox individuals. The home range overlap in warm season ((?) =0.24, SD = 0.12) is significantly lower than that in cold season ((?) = 0.36, SD = 0.19) (Mann-Whitney U, Z = -1.037, P = 0.300) . The overlap between home range cores is significantly lower than that between home ranges (Mann-Whitney U, Z = -3.112, P = 0.001) .4. Based on the behaviors and spatial distributions of resource use, we partitioned home ranges into 4 main functional regions: core active region, core inactive region, peripheral active region, and peripheral inactive region. We measured biological characteristics of each region. Core active regions ((?) - 0.45km2, SD = 0.16) were smaller than core inactive regions ((?) = 0.51 km2, SD = 0.16), and the peripheral active regions ((?) = 0.84km2, SD = 0.12) were larger than peripheral inactive regions ((?) = 0.63 km2, SD = 0.19). Pika (Ochotona curzoniae) densities in both the core active region (Mann-Whitney U test, Z=-9.310, P = 0.000) and peripheral active region (Mann-Whitney U test, Z=-4.762, P = 0.000) were significantly higher than those in counterpart inactive regions. Compared with core inactive regions, core active regions were more likely to be located in areas with gentle slopes (Mann-Whitney U test, Z =-3.011, P = 0.003) , lower elevations(Mann-Whitney U test, Z =-2.570, P = 0.000) and lower positions on slopes(χ~2 =23.229, df- 5, P=0.000) . Compared with peripheral inactive regions, lowerslope positions (χ~2 =11.257, df- 5, P= 0.047) were preferred by Tibetan foxes forperipheral active areas, whereas slope (Mann-Whitney U test, Z =-1.778, P = 0.075)and elevation (Mann-Whitney U test, Z =-0.881, P = 0.378) did not differ.5. Habitat selection of Tibetan fox was studied based on multi-linear regression model. Pika density, terrain ruggedness, slope and elevation are all important impacts on habitat selection by Tibetan fox. In warm season, the most parsimonious model contains pika density, the quadratic term of pika density, terrain ruggedness, slope, elevation, the interaction between pika density and terrain ruggedness, the interaction between pika density and slope (k = 8), the AICcw value is 0.998; In cold season, the most parsimonious model contains pika density, the quadratic term of pika density, terrain ruggedness, slope, elevation, the interaction between pika density and slope (k = 7, AICcw = 0.374) . There is no-linear relationship between pika density and utilization distribution, and Tibetan fox more prefer moderate pika density areas; Tibetan fox keep avoidance to higher elevations, use terrain ruggedness with no-linear selection and showed reverse selection on slope in different season. The distances of fox locations from river ((?) = 806.4 m, SD = 301.9) are significantly shorter than those of random points((?) = 917.9 m, SD = 467.6) (ANOVA, F= 7.876, P = 0.005). Comapred with random points, Tibetan fox shows positive selection to road (ANOVA, F = 10.556, P = 0.001), and did not avoid human activities (ANOVA, F = 2.830, P = 0.093) .6. Tibetan fox dens were classified into natal dens and resting burrows. Tibetan foxes did not use special slope aspects for natal dens (Rayleigh Test, P > 0.05) , but use sunny ((?) =43.0°,SD =6.9) and half-sunny ((?)=98.2°,SD=18.0) slope aspects for resting burrows (Rayleigh Test, P < 0.05) . Tibetan fox choose more rugged area for both natal dens and resting burrows (Mann-Whitney U Test, P < 0.05) . The visible viewshed gird number of natal den and resting burrow sites were significantly larger than those of random points (Mann-Whitney U Test, P < 0.05) . Resting burrows located at areas with steeper slopes, lower pika abundance, smaller distance to other dens. Locations of dens and burrows were not significantly affected by elevation, sun index, distances to river and road. Tibetan foxes did not avoid manmade features for their resting natal dens and resting burrows (Mann-Whitney U Test, P> 0.05) .7. The diet composition of Tibetan fox was analyzed by frequency of occurrence method based on scat-analysis in periods of September-October (high pika density) and March-May (low pika density) . The food items contain plateau pika, rodents, marmmot, yak, birds, reptile, insect and plant. Tibetan fox did not prey food item randomly ( September-October,χ~2 =360.61, df = 9, P = 0.000; March-April,χ~2 =358.17, df = 10, P = 0.000) . Black lipped pika ((?) =84.8%, SD=10.6) and rodents ((?)=17.3%, SD=13.4) served as the main food components of Tibetan fox. Marmot, Blue sheep, Tibetan gazelle were found in fox scats, and more frequently detected in March-May season. In September-October season, the pika density ((?)= 4.15, 95% confidence interval is 3.42 - 4.88) is significantly higher than that in March-May season ((?) = 2.67, 95% confidence interval is 2.31 -3.03) (U= 2376, Z= -3.961, P < 0.001), but the diet composition of Tibetan fox did not significantly changed (χ~2 = 9.14, df=11,P = 0.609) . The food niche breadth of Tibetan fox is 1.32, the Shannon-Weaver diversity index and evenness index are separately 2.29 and 0.66. 8. Habitat quality evaluation: Based on "Presence data", we assessed the habitat quality of Tibetan fox in Gouli Township, Dulan County, Qinghai Province, China. We also estimated the spatial carrying capacity of Tibetan fox according to their minimum space requirements. A total of 4 topographical factors, elevation, slope, terrain ruggedness and slope position, were used to conduct habitat assessment for Tibetan fox. The suitability of habitat factors were determined by comparing the utilization by Tibetan fox and its availability based on 95% Bonferroni confidence interval. A comprehensive assessment criterion was set up for all topographic factors. For Tibetan fox, the elevations of 4050-4300m, the slopes of 5-20°, the upper and lower slope positions were suitable habitat. Tibetan fox use terrain ruggedness non-selectively. According to the utilization of Tibetan fox on different topographic factors and the consistence of habitat utilization by different fox individuals, we setthe comprehensive criterion as: (?). The area of suitable habitat is about 17.4 km~2, which take a percentage of 38.8% of research area. The area of most suitable habitat is only 0.4 km~2. The home range of Tibetan fox ranges from 2.53 km~2 to 4.99 km~2, and the overlap index (OI) of different individuals were 0.16-0.66. The minimum space requirements of Tibetan fox are 2.09-3.55 km~2, and the spatial carrying capacity of Tibetan fox in suitable habitat is 7-12.9. Index of pika abundance was used to investigate the spatial density distribution characteristics. The pika density in warm season is significantly higher than that in cold season (U = 2376, Z = -3.961, P < 0.001) , and the spatial distribution changed. The pika density distribution was correlated with elevation attributes (y = -20.484 x~2 + 20.501 x,r~2= 0.324), the pika density will decrease with the enhancement of elevation, when the elevation attributes reached 4300 m, the pika density will not decrease any more. The regression relationship between pika density and slope was: y = -0.784 x~2 + 0.737 x, r~2 = 0.218, and plateau pika prefer flat or most rugged areas (y= 1.415 x~2-1.455 x, r~2=0.246) .
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