Impact of marine-subsidized predators on lemming-plant oscillations

Abstract

Questions: Assuming that arctic lemming oscillations are generated by interactions between lemmings and depletable plants, how should these oscillations change in response to varying densities of marine-subsidized predators and differences in the production of herbaceous forage? Are the patterns thus generated consistent with existing data? Features of the model: Rosenzweig-type predator–prey model, with lemmings interacting with depletable plants and herbaceous plants. The impact of marine-subsidized predators is included as an extra mortality factor, influencing lemmings in summer. Ranges of parameters: We set the carrying capacity of depletable plants at 2000 kg ·ha−1. We used carrying capacities for herbaceous plants of 1000 kg ·ha−1 (grassland/meadow) and 100 kg ·ha−1 (heath). In the absence of predation, we assume that the population growth rate of lemmings in summer is zero when their foraging rate is 44 % of the saturation rate. In subsequent simulations, we successively increased the foraging rate required for a zero population growth rate to simulate the impact of a successively larger pool of marine-subsidized predators.