Dynamic effects of predators on cyclic voles: field experimentation and model extrapolation

Mechanisms generating the well-known 3-5 year cyclic fluctuations in densities of northern small rodents (voles and lemmings) have remained an ecological puzzle for decades. The hypothesis that these fluctuations are caused by delayed density-dependent impacts of predators was tested by replicated f...

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Published in:Proceedings of the Royal Society. B, Biological sciences Biological sciences, 2002-05, Vol.269 (1495), p.991-997
Main Authors: Korpimäki, Erkki, Norrdahl, Kai, Klemola, Tero, Pettersen, Terje, Stenseth, Nils Chr
Format: Article
Language:English
Subjects:
Animals
Arvicolinae - physiology
Breeding
Carnivora
Demographic Model
Finland
Hares
Modeling
Models, Biological
Owls
Population Cycle
Population Density
Population dynamics
Population ecology
Predation
Predator Reduction Experiment
Predator-Prey Interactions
Predators
Predatory Behavior - physiology
Raptors
Reproducibility of Results
Rodents
Time Factors
Voles
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Summary:Mechanisms generating the well-known 3-5 year cyclic fluctuations in densities of northern small rodents (voles and lemmings) have remained an ecological puzzle for decades. The hypothesis that these fluctuations are caused by delayed density-dependent impacts of predators was tested by replicated field experimentation in western Finland. We reduced densities of all main mammalian and avian predators through a 3 year vole cycle and compared vole abundances between four reduction and four control areas (each 2.5-3 km2). The reduction of predator densities increased the autumn density of voles fourfold in the low phase, accelerated the increase twofold, increased the autumn density of voles twofold in the peak phase, and retarded the initiation of decline of the vole cycle. Extrapolating these experimental results to their expected long-term dynamic effects through a demographic model produces changes from regular multiannual cycles to annual fluctuations with declining densities of specialist predators. This supports the findings of the field experiment and is in agreement with the predation hypothesis. We conclude that predators may indeed generate the cyclic population fluctuations of voles observed in northern Europe.
ISSN:0962-8452
1471-2954
DOI:10.1098/rspb.2002.1972