Modelling activity synchronisation in free-ranging microtine rodents

The short-term rhythm of activity in microtine rodents is persistent on the population level even with increasing density, which is regarded as eviden ce for social synchronisation in the literature. Based on empirical data fr om a field study we developed an individual-based model to test the rationa le behind this argument. The model considered two aspects: (1) the activity behaviour of 10 to 100 individuals; and (2) the probability of activity re cording. We have modelled five different mechanism of activity synchronisat ion, ranging from no synchronisation over entrainment by sunrise and sunset to strong social synchronisation. We then examined density dependence of t he resultant population level pattern quantitatively. The analysis revealed that the pattern persists with increasing density irrespective of the supp osed mechanism of activity synchronisation, so the argument for social sync hronisation does not hold. We discuss this finding and give an outlook how the model may be used as a conceptual framework to approach other problems related to microtine activity behaviour. Our model may also serve as an exa mple for a useful technique to evaluate methodological issues, in which a v irtual reality is compared with its image derived from data analysis. (C) 1 999 Elsevier Science B.V. All rights reserved.