POPULATION-CYCLES AND SPATIAL PATTERNS IN SNOWSHOE HARES - AN INDIVIDUAL-ORIENTED SIMULATION

The issue of population cycles in mammals is reviewed and focused on t he particular case of the snowshoe hare spatiotemporal dynamics. We ha ve tested some hypotheses by means of an individual-oriented simulatio n. The results suggest that a lagged response to food supply is able t o generate cycles, which can be qualitatively very similar to the obse rved held fluctuations. Surprisingly spatial structures, as target pat terns and spiral waves, emerge from the trophic interactions despite t he random rules in the simulation. These macroscopic patterns can expl ain the observed synchronization in hare dynamics over large areas, wh ich has been recently reported. Furthermore, the formation of spiral w aves can explain the U-shape pattern in the synchronization vs. distan ce plot observed by Ranta and co-workers. Population cycles and spatia l patterns go together. An increase in the maximum vegetation availabl e acts as a bifurcation parameter, inducing cycles when it is up to a given threshold. Some ''simulation experiments'' are performed, and th e results are discussed in the light of field observations and theoret ical predictions. (C) 1997 Academic Press Limited.