, Volume 10, Issue 4, pp 607–622 | Cite as

Can Reindeer Overabundance Cause a Trophic Cascade?

  • Rolf A. Ims
  • Nigel G. Yoccoz
  • Kari Anne Bråthen
  • Per Fauchald
  • Torkild Tveraa
  • Vera Hausner


The region Finnmark, in northernmost Europe, harbors dense populations of semi-domestic reindeer of which some exhibit characteristics of overabundance. Whereas overabundance is evident in terms of density-dependent reductions in reindeer body mass, population growth and abundance of forage plants, claims have been made that this reindeer overabundance also has caused a trophic cascade. These claims are based on the main premise that reindeer overgrazing negatively impacts small-sized, keystone tundra herbivores. We tested this premise by a large-scale study in which the abundance of small rodents, hares and ptarmigans was indexed across reindeer management districts with strong differences in stocking densities. We examined the scale-dependent relations between reindeer, vegetation and these small-sized herbivores by employing a spatially hierarchical sampling design within the management districts. A negative impact of reindeer on ptarmigan, probably as a result of browsing reducing tall Salix, was indicated. However, small rodents (voles and lemmings), which are usually the keystone herbivores in the plant-based tundra food web, were not negatively impacted. On the contrary, there was a strong positive relationship between small rodents and reindeer, both at the scale of landscape areas and local patches, with characteristics of snow-bed vegetation, suggesting facilitation between Norwegian lemmings and reindeer. We conclude that the recent dampening of the vole and lemming population cycle with concurrent declines of rodent predators in northernmost Europe were not caused by large herbivore overgrazing.


tundra lemming ptarmigan facilitation food web overgrazing quasi-experiment Salix spatial scaling growth forms 



We are grateful to Johan Ingvald Hætta and Anders Aarthun Ims for information about reindeer herding districts, to Torstein Engelskjøn for providing a flora database, Bernt Johansen for providing satellite images, The Norwegian Coast Guard and Jan Kåre Amundsen for transportation during field work, Sunna Pentha for field assistance, and to Marianne Iversen and Siw Killengreen for great leadership during field work. This study, which is a contribution from the “Ecosystem Finnmark” project, was financed by the Norwegian Research Council.


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Copyright information

© Springer Science+Business Media, LLC 2007

Authors and Affiliations

  • Rolf A. Ims
    • 1
    • 2
  • Nigel G. Yoccoz
    • 1
    • 2
  • Kari Anne Bråthen
    • 1
  • Per Fauchald
    • 1
    • 2
  • Torkild Tveraa
    • 2
  • Vera Hausner
    • 1
  1. 1.Department of BiologyUniversity of TromsøTromsøNorway
  2. 2.Department of Arctic EcologyNINA, Polar Environmental CentreTromsøNorway

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