title: Sheep grazing and rodent populations: evidence of negative interactions from a landscape scale experiment.
abstract: Inter-specific competition, facilitation and predation influence herbivore assemblages, but no study has experimentally explored the interactions between large ungulates and small rodents. In a fully replicated, landscape scale experiment, we manipulated densities of domestic sheep in mountain pastures in Norway. We then determined population growth and densities of rodents by live trapping in each of the areas with different sheep densities. We found that the (summer) population growth rate and autumn density of the field vole (Microtus agrestis) was lower at high sheep density. This provides the first experimental evidence of negative interactions between an ungulate and small rodent species. There was no effect on the bank vole (Clethrionomys glareolus), whose diet differs from sheep. Sheep density, therefore, potentially alters the pattern of inter-specific population synchrony amongst voles. Our study shows that negative interactions between large ungulates and small rodents may be species-specific and negative population consequences for the rodent population appear above threshold ungulate densities.
authors.affiliation: Program for Experimental Behavioral and Ecological Research (EBE), Department of Biology, University of Oslo, P.O. Box 1066 Blindern, N-0316 Oslo, Norway.
authors.forename: Harald
authors.initials: H
authors.lastname: Steen
authors.forename: Atle
authors.initials: A
authors.lastname: Mysterud
authors.forename: Gunnar
authors.initials: G
authors.lastname: Austrheim
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000502:physiology*; D003163:Competitive Behavior / Q000502:physiology; D017753:Ecosystem; D008954:Models, Biological; D009664:Norway; D011156:Population Density; D011157:Population Dynamics; D012621:Seasons; D012756:Sheep / Q000502:physiology*; D013045:Species Specificity
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