POPULATION-DYNAMICS OF TERRITORIAL SPECIES IN SEASONAL AND PATCHY ENVIRONMENTS

We present a seasonal model of a population in which there are differences between individuals. Dominant individuals defend breeding/feeding territories and are always assumed to obtain sufficient resources during the summer; in the winter there is no breeding, no territorial defence, and no individual differences. During the summer there is contest competition, and during the winter there is scramble competition. We study the effect of varying the length of the winter and summer seasons relative to each other, and varying the degree of patchiness in the distribution of food resources. Both longer winters and more patchily distributed resources decrease the stability of the population from year to year, causing it to exhibit cyclic behavior of increasing period and ultimately chaotic dynamics and population crashes. The kind of resource patchiness implemented in this model has a different effect on the population dynamics than in most patch models, where increased patchiness is generally considered to have a stabilizing effect. We discuss our results in light of observed mammal cycles in the the arctic and north temperate zone, and particularly with respect to the tendency for northern populations to be more cyclic than southern populations.