S1 Appendix- Predicting the abundance of small rodents at each roe deer fawn bed-site
During spring-summer 2003-2004, parallel to the study on roe deer fawns, we performed a capture-mark recapture study (Panzacchi et al. 2010)to investigate the distribution of small rodents with respect to the same habitat types and vegetation characteristics recorded for roe deer fawns. The study design was based on Small Quadrates (SQs, Myllmäki et al. 1971), which are 15 x 15 m trapping units composed of 12 live-traps positioned along the perimeter. Note that this design mirrors that of the study on roe deer fawns, as both the sampling unit (i.e. 15 x 15 m quadrates) and all environmental parameters recorded within are identical. With a trapping effort of 100 days and a total of 190 SQs distributed in each habitat type we trapped, marked and released 674 different individuals belonging to 8 species. By using the software mark 4.3 (White and Burnham 1999) we estimated the abundance of the three most common rodent species - i.e. field vole Microtus agrestis,bank vole Myodes glareolus, and wood mouse Apodemus sylvaticus in each habitat. The resulting index, sr.hab (see Fig. 1), was used as a proxy of the abundance of rodents within each habitat type a fawn was located in. In addition, we predicted the site-specific abundance of rodents at each roe deer fawn bed-site based on the link between rodent abundance and the vegetation characteristics. This index, sr.bed, reflects the abundance of rodents within the 15 x 15 m surrounding each roe deer fawn bed-site. sr.bed was obtained as follows. First, we modelled the abundance of rodents with vegetation characteristics in each SQ by using glms with a negative binomial error structure. Then, the parameter estimates of the most parsimonious models (see Table S1) were used to predict the number of rodents within the 15 x 15 m surrounding each fawn location, based on vegetation characteristics recorded within. To obtain sr.hab and sr.bed, the population estimates for each rodent species were first corrected according to the predator preferences for different species of rodents, and then summed up within each habitat. The correction factor was obtained from a previous study on the diet of red foxes (Panzacchi et al. 2008b) by multiplying the number of M. agrestis (preferred prey) by 1.00, M. glareolus by 0.077 and A. sylvaticus by 0.038, according to their frequency of occurrence relative to the preferred species in the diet.
The most parsimonious models explaining the number of small rodents trapped with respect to vegetation characteristics are presented in Table S1. The abundance of M. glareolus was correlated positively to that of raspberries (p = 0.045) and negatively to moss (p = 0.014), herbaceous plants (p = 0.003), crop and branches (p < 0.001). M. agrestis increased with the abundance of herbaceous plants, raspberries, bushes, branches and crop (p < 0.001). Finally, the abundance of A. sylvaticus was higher in cultivated fields (p < 0.001).
Table S1
Set of best performing generalised linear models describing the relationship between the abundance of M. agrestis, M. glareolus and A. sylvaticus and vegetation characteristics at each trapping site. Models are ranked with the most parsimonious model on top of each list. For each model, we present the parameter estimates (loge-scale), the Akaike’s weights, ωi, and the number of parameters (k).
Species / Models / ∆AICc / ωi / kM. glareolus
0.013 tall berries - 0.034 branches - 0.034 cereals - 0.009 herbs - 0.025 moss / 0.000 / 0.521 / 6
- 0.039 branches - 0.040 cereals - 0.016 herbs - 0.028 moss - 0.007 small berries / 1.317 / 0.265 / 6
0.010 tall berries - 0.036 branches - 0.037 cereals - 0.012 herbs - 0.026 moss - 0.003 small berries / 1.664 / 0.214 / 7
M. agrestis
0.030 branches + 0.051 bushes + 0.037 cereals + 0.056 herbs + 0.044 tall berries / 0.000 / 0.433 / 6
0.014 bushes + 0.020 herbs - 0.060 moss - 0.032 small berries / 0.228 / 0.386 / 5
0.026 branches + 0.045 bushes + 0.032 cereals + 0.051 herbs - 0.022moss + 0.039 tall berries / 1.749 / 0.181 / 7
A. sylvaticus
0.017 cereals / 0.000 / 0.475 / 2
0.017 cereals - 0.026 tall berries / 0.967 / 0.311 / 3
0.016 cereals - 0.012 bushes / 1.433 / 0.232 / 3