Table 2 

Regression models for the effect of density (number of females per enclosure) on variables of reproduction, space use and physiology in enclosure experiments on bank voles. 

study 
variable 
model 
R2 
n 
F 
p 
coefficient a 
constant b 


moderate densities (420 bank vole females/ha) 

breeding females 
inverse 
0.230 
38 
12.1 
0.001 
3.37 
3.78 

breeding females 
linear 
0.265 
38 
14.3 
0.001 
0.43 
1.1 



moderate to high densities (1242 bank vole females/ha) 

breeding females 
linear 
0.817 
12 
50.2 
< 0.001 
0.83 
2.33 

breeding females 
inverse 
0.674 
12 
23.7 
0.001 
70.6 
14.2 

mean litter size 
linear 
< 0.01 
12 
< 0.01 
0.931 



mean home range 
inverse 
0.789 
12 
37.5 
< 0.001 
2420 
364 

interaction (nr. of females) 
linear 
0.653 
12 
18.9 
0.001 
0.45 
0.58 

captures/animal 
linear 
0.3 
12 
4.2 
0.065 
0.21 
8.7 



Log(FGM 1^{st}week 
inverse 
0.035 
6 
0.1 
0.723 

Log(FGM 2^{nd}week) 
inverse 
0.8 
6 
16 
0.016 
4.6 
2.9 

Log(FGM 3^{rd }week) 
inverse 
0.562 
6 
5.1 
0.086 



We tested linear model (y = ax+b) and/or an inverse models (y = a/x+b), the latter indicating a threshold value (constant b) for high densities. Analyses were based on populations (rates or enclosure means). 38 Populations at moderate densities were investigated over 4 years in different earlier experiments (see text), 12 populations in moderate to high densities were investigated during the 2year experiment reported here. 

Eccard et al. BMC Ecology 2011 11:16 doi:10.1186/147267851116 