Phase- and density-dependent population dynamics in Norwegian lemmings: interaction between deterministic and stochastic processes

• Published in: Proceedings of the Royal Society of London. Series B: Biological Sciences
• Main Authors: Stenseth, Nils C., Chan, Kung-Sik, Framstad, E., Tong, Howell
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: The Royal Society 1998
• Subjects: QL Zoology; QA Mathematics (inc Computing science); QH301 Biology; Norway; Lemmus lemmus
• Online Access: https://kar.kent.ac.uk/17174/; https://doi.org/10.1098/rspb.1998.0526

We analysed two 26-year long (1970-1995) time-series on annual population growth rates of Norwegian lemmings (Lemmus lemmus) from Finse, south Norway, using a threshold autoregressive (TAR) approach. We demonstrate that the population dynamics is both phase- and density-dependent. The phase-dependence accounts for the observed nonlinearity. We used the deduced stochastic model structure as a basis for evaluating the dynamic properties of this system. The dynamics is characterized either by limit cycles or chaos (the latter with a strong semi-periodic component). Stochasticity is seen to play an important role in the determination of the periodicity. The ecological implications of these statistical and mathematical results are discussed.