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Phase- and density-dependent population dynamics in Norwegian lemmings: interaction between deterministic and
N C Stenseth1, K S Chan, E Framstad
1Centre for Advanced Study, Norwegian Academy of Science and Letters, Oslo, Norway. n.c.stenseth@bio.uio.no
Proceedings. Biological Sciences
|November 20, 1998
Summary
Norwegian lemming population dynamics exhibit phase- and density-dependence, leading to nonlinear patterns. Mathematical modeling revealed complex dynamics, including limit cycles or chaos, influenced by stochasticity.
Area of Science:
- Ecology
- Population Dynamics
- Mathematical Biology
Background:
- Understanding population fluctuations is crucial for ecological management.
- Norwegian lemmings (Lemmus lemmus) exhibit cyclical population dynamics.
- Previous studies suggest complex interactions influencing lemming populations.
Purpose of the Study:
- To analyze long-term population growth rates of Norwegian lemmings.
- To identify the underlying mechanisms driving population dynamics.
- To evaluate the dynamic properties of the lemming population system.
Main Methods:
- Analysis of two 26-year time-series (1970-1995) of annual population growth rates.
- Application of a threshold autoregressive (TAR) modeling approach.
- Deduction of a stochastic model structure for dynamic property evaluation.
Main Results:
- Population dynamics are demonstrated to be both phase- and density-dependent.
- Phase-dependence explains the observed nonlinearity in population trends.
- The system exhibits dynamics characterized by limit cycles or chaos, with stochasticity influencing periodicity.
Conclusions:
- The study reveals complex, nonlinear dynamics in Norwegian lemming populations.
- Stochastic factors play a significant role in determining population cycle periodicity.
- The findings have implications for understanding and managing cyclic rodent populations.