Home range dynamics and population regulation: An individual-based model of the common shrew Sorex araneus

Many territorial animals show marked home range dynamics. Depending on food resources and the presence of other individuals, the size, shape and location of home ranges can change even on short time scales. Home range dynamics are thus likely to be an important aspect of population regulation. Most existing models, however, assume static home ranges. We therefore present an individual-based model that describes home range dynamics on a daily time scale. As an example organism, we focus on the common shrew (Sorex araneus), which shows a marked territorial behaviour. The proximate purpose of the model is to capture the relation between home range dynamics and population dynamics. The ultimate purpose is to develop a model that can be used for predicting effects of changes in agricultural practice and pesticide risk assessment. In the model, home ranges are represented by a number of cells in a landscape which are used by a particular individual. They are constantly adapted in order to provide sufficient food resources for an animal. When home ranges do not provide sufficient resources, animals disperse. The model is able to reproduce site fidelity of individuals, habitat preference, and dispersal. Population densities in a mixed habitat structure resulted in densities approximately equal to those reported from field studies. It is shown that home range size and dispersal are density-dependent and therefore likely to have a strong effect on regulation. We conclude (1) that the basic design of our model is also applicable for other species showing a marked home range behaviour, and (2) that a realistic representation of population regulation might require explicit modelling of home range behaviour.