title: Indirect food web interactions mediated by predator-rodent dynamics: relative roles of lemmings and voles.
abstract: Production cycles in birds are proposed as prime cases of indirect interactions in food webs. They are thought to be driven by predators switching from rodents to bird nests in the crash phase of rodent population cycles. Although rodent cycles are geographically widespread and found in different rodent taxa, bird production cycles appear to be most profound in the high Arctic where lemmings dominate. We hypothesized that this may be due to arctic lemmings inducing stronger predator responses than boreal voles. We tested this hypothesis by estimating predation rates in dummy bird nests during a rodent cycle in low-Arctic tundra. Here, the rodent community consists of a spatially variable mix of one lemming (Lemmus lemmus) and two vole species (Myodes rufocanus and Microtus oeconomus) with similar abundances. In consistence with our hypothesis, lemming peak abundances predicted well crash-phase nest predation rates, whereas the vole abundances had no predictive ability. Corvids were found to be the most important nest predators. Lemmings appear to be accessible to the whole predator community which makes them particularly powerful drivers of food web dynamics.
authors.affiliation: Department of Arctic and Marine Biology, University of Tromsø, , Tromsø 9037, Norway.
authors.forename: Rolf A
authors.initials: RA
authors.lastname: Ims
authors.forename: John-André
authors.initials: JA
authors.lastname: Henden
authors.forename: Anders V
authors.initials: AV
authors.lastname: Thingnes
authors.forename: Siw T
authors.initials: ST
authors.lastname: Killengreen
mesh_terms: D000818:Animals; D001110:Arctic Regions; D003411:Arvicolinae / Q000502:physiology*; D001717:Birds / Q000502:physiology*; D017753:Ecosystem; D004531:Eggs; D020387:Food Chain; D009425:Nesting Behavior / Q000502:physiology; D009664:Norway; D011156:Population Density; D011157:Population Dynamics; D011235:Predatory Behavior; D012044:Regression Analysis; D012306:Risk; D013997:Time Factors
keywords: alternative prey mechanism; dummy nests; functional traits; predation