Roman Andrzejewski

The home-range concept in rodents revised

The paradigm regarding the ecology of populations of small rodents has had several basic theses: (1) the individual has a home range or is a migrant; (2) factors regulating population parameters (including density) include spatio-social relations between individuals; and (3) the phenomena observed on trial plots with a system of live traps are the same as those beyond the plot. However, the home-range concept in small rodents is open to criticism in that: (1) observations point to much greater ranges of spatial activity in these animals than has been shown hitherto in plot-based studies with systems of live traps; (2) there is great variability in the directions and extent of the spatial activity of small rodents; (3) observations suggest that what is regarded as the area of spatial activity of an individual has limited information content since the ‘tenant’ makes use of the area via tracks and trails along which it moves. Transfers of studies on odour-related information in small rodents from the laboratory to natural populations confirm the significance of odours in the life of these animals and in integrating their populations. It is possible that the need to leave information in the environment (informational conditioning) provokes considerable locomotory and spatial activity in small rodents. Live traps with bait (food) limit the spatial activity of animals. The set of traps in which an individual is caught thus represents not home range but trap range. A new paradigm for the ecology of small rodents should comprise the propositions that: (1) the function of olfactory information is the integration of a population into an ecological system; (2) the maintenance of odour-mediated conditioning in the environment is one of the reasons for locomotor and spatial activity; (3) the patchy distribution of food in the environment (including study plots with traps) gives rise to changes in the use made of space by individuals; (4) the phenomena observed on research plots with live traps containing bait are different to those ongoing at the same time outside these areas. Such a paradigm requires reinterpretation of research results obtained hitherto as well as the application of new research methods.