A HOME RANGE MODEL INCORPORATING BIOLOGICAL ATTRACTION POINTS

SUMMARY (1) A distinction is made between the domain and utilization distribution of an animal's space-use pattern, and the need for a reappraisal of model-based approaches to the description of utilization distributions is indicated. In particular, the symmetry of the widely used bivariate normal model is considered to provide an inadequate characterization of individual space-use intensity in many ecological situations. (2) A field worker is often aware of the position of biological attraction points, termed nuclei, of which there may be several for a particular home range. There is evidence that such nuclei have important influences over the space utilization intensity of a given individual. The home range model proposed here assumes a circular normal distribution of activity about each nucleus. The strength and range of the attractive fields about each nucleus are parameters which may be estimated. (3) Independent fixes of an individual's locations are used to obtain model parameter estimates using the Maximum Likelihood method, enabling a description of the utilization distribution, and calculation of probability domains. (4) The model is applied to field data collected from the grey squirrel (Sciurus carolinensis, Gmelin) and a hypothetical data set. The resulting domain and utilization distribution properties are discussed in relation to the bivariate normal model, and various advantages of the present model are demonstrated.