Changes in seasonality and dynamics of the rodent-mustelid system

Population cycles of small rodents are a fascinating ecological phenomenon which is characterized by high amplitudes in the Arctic and influenced by complex interactions with predators. These cycles are also shaped by environmental factors, such as snow cover and season length, which are increasingly affected by global change. Arctic amplification has led to longer snow-free seasons and growing seasons. This raises questions about stability of the rodent cycles and long-term dynamics of the system. This study analyzes a seasonal predator–prey model parametrized for the rodent-mustelid system in northern Fennoscandia. By employing a new methodology that incorporates smooth seasonal transitions, we provide a more comprehensive exploration of the system’s long-term behavior. Using dynamical systems tools such as Poincaré mapping and clustering for behavior classification, we investigate the influence of longer snow-free periods and density dependence of the predator on system dynamics. Through simulations with realistic parameter values and many possible initial abundances, six qualitatively distinct system behaviors were identified, including chaos, multi-year cycles, quasi-periodic orbits, and their mutual coexistence. Longer summers and low density dependence values have a stabilizing effect on the system dynamics. Long summers with higher density dependence values result in quasi-periodic orbits. The interplay between summer length and density dependence underscores a significant gap in empirical data and emphasizes the need for comprehensive long-term monitoring of ecological systems.