Density Dependence in Time Series of the Fossorial Form of the Water Vole, Arvicola terrestris

regulatory effects was obscured by linear and nonlinear trends in one and two cases, respectively. The data support the hypothesis that time-delayed and nonlinear mechanisms of population regulation oper- ate in fossorial populations of A. terrestris. Furthermore, the data are consistent with regulatory mechanisms involving predator-prey interactions, while the causation of the unusually long cycle is still an open question. Finally, the presence of trends in these time series suggests that water vole populations track some long-term climatic changes in the environment.