Oecologia

, Volume 168, Issue 1, pp 141–151 | Cite as

The importance of willow thickets for ptarmigan and hares in shrub tundra: the more the better?

  • Dorothée Ehrich
  • John-André Henden
  • Rolf Anker Ims
  • Lilyia O. Doronina
  • Siw Turid Killengren
  • Nicolas Lecomte
  • Ivan G. Pokrovsky
  • Gunnhild Skogstad
  • Alexander A. Sokolov
  • Vasily A. Sokolov
  • Nigel Gilles Yoccoz
Plant-Animal interactions - Original Paper

Abstract

In patchy habitats, the relationship between animal abundance and cover of a preferred habitat may change with the availability of that habitat, resulting in a functional response in habitat use. Here, we investigate the relationship of two specialized herbivores, willow ptarmigan (Lagopus lagopus) and mountain hare (Lepus timidus), to willows (Salix spp.) in three regions of the shrub tundra zone—northern Norway, northern European Russia and western Siberia. Shrub tundra is a naturally patchy habitat where willow thickets represent a major structural element and are important for herbivores both as food and shelter. Habitat use was quantified using feces counts in a hierarchical spatial design and related to several measures of willow thicket configuration. We document a functional response in the use of willow thickets by ptarmigan, but not by hares. For hares, whose range extends into forested regions, occurrence increased overall with willow cover. The occurrence of willow ptarmigan showed a strong positive relationship to willow cover and a negative relationship to thicket fragmentation in the region with lowest willow cover at landscape scale, where willow growth may be limited by reindeer browsing. In regions with higher cover, in contrast, such relationships were not observed. Differences in predator communities among the regions may contribute to the observed pattern, enhancing the need for cover where willow thickets are scarce. Such region-specific relationships reflecting regional characteristics of the ecosystem highlight the importance of large-scale investigations to understand the relationships of habitat availability and use, which is a critical issue considering that habitat availability changes quickly with climate change and human impact.

Keywords

Habitat use Habitat fragmentation Occupancy Availability Large scale 

Notes

Acknowledgments

We are grateful to Eeva Soininen, Ingrid Jensvoll, Anna Rodnikova, Victor Sidorov, Olga Kulikova and many others for great contributions to the field work, and we thank two anonymous reviewers for their comments on a previous version of the paper. This study was financed by the Research Council of Norway through the projects “EcoFinn” and “IPY-Arctic Predators” (http://www.arctic-predators.uit.no).

Supplementary material

442_2011_2059_MOESM1_ESM.doc (140 kb)
Supplementary material 1 (DOC 139 kb)

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Dorothée Ehrich
    • 1
  • John-André Henden
    • 1
  • Rolf Anker Ims
    • 1
  • Lilyia O. Doronina
    • 2
  • Siw Turid Killengren
    • 1
  • Nicolas Lecomte
    • 1
  • Ivan G. Pokrovsky
    • 1
    • 3
  • Gunnhild Skogstad
    • 1
  • Alexander A. Sokolov
    • 4
  • Vasily A. Sokolov
    • 5
  • Nigel Gilles Yoccoz
    • 1
  1. 1.Department of Arctic and Marine BiologyUniversity of TromsøTromsoNorway
  2. 2.Biological Faculty of Lomonosov Moscow State UniversityMoscowRussia
  3. 3.A.N. Severtsov Institute of Ecology and EvolutionRussian Academy of SciencesMoscowRussia
  4. 4.Ecological Research Station of the Institute of Plant and Animal EcologyUral Division Russian Academy of SciencesYamalo-Nenetski districtRussia
  5. 5.Institute of Plant and Animal EcologyUral Division Russian Academy of SciencesEkaterinburgRussia

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