Figure 1

A: Conceptual model of density dependence of the number of breeders and the proportion of breeders in territorial species. (S) Saturation point where all territories are occupied and breeding suppression begins. B: Empirical evidence for density dependence in 38 enclosed experimental bank vole populations at moderate densities [5, 25–28, 41]. The size of the symbol represents the number of population with the same value. C: Results of the experiment (this paper) extending the density range of enclosed bank vole populations to medium and high densities. Each symbol represents one population. D: Conceptual model of a territorial species breeding suppression (control) at moderate densities (from density S to density C) and release of suppression (incomplete control) at higher densities (density > C, C can be compared with the 'competition point' in eusocial insects).