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Impacts of predator-mediated interactions along a climatic gradient on the population dynamics of an alpine bird

  • Bowler, Diana E.1, 2, 3, 4
  • Kvasnes, Mikkel A. J.4
  • Pedersen, Hans C.4
  • Sandercock, Brett K.4
  • Nilsen, Erlend B.4, 5
  • 1 Department of Ecosystem Services, German Centre for Integrative Biodiversity Research (iDiv), Putschstr. 4, 04103 Leipzig , (Germany)
  • 2 Institute of Biodiversity, Friedrich Schiller University Jena, Dornburger Straße 159, 07743 Jena , (Germany)
  • 3 Department of Ecosystem Services, Helmholtz Center for Environmental Research—UFZ, Permoserstraße 15, 04318 Leipzig , (Germany)
  • 4 Department of Terrestrial Biodiversity, Norwegian Institute for Nature Research, P.O. 5685 Torgarden, 7485 Trondheim , (Norway)
  • 5 Nord University, Faculty of Biosciences and Aquaculture, Steinkjer , (Norway)
Published Article
Proceedings of The Royal Society B Biological Sciences
The Royal Society
Publication Date
Dec 23, 2020
DOI: 10.1098/rspb.2020.2653
PMID: 33352076
PMCID: PMC7779518
PubMed Central


According to classic theory, species' population dynamics and distributions are less influenced by species interactions under harsh climatic conditions compared to under more benign climatic conditions. In alpine and boreal ecosystems in Fennoscandia, the cyclic dynamics of rodents strongly affect many other species, including ground-nesting birds such as ptarmigan. According to the ‘alternative prey hypothesis’ (APH), the densities of ground-nesting birds and rodents are positively associated due to predator–prey dynamics and prey-switching. However, it remains unclear how the strength of these predator-mediated interactions change along a climatic harshness gradient in comparison with the effects of climatic variation. We built a hierarchical Bayesian model to estimate the sensitivity of ptarmigan populations to interannual variation in climate and rodent occurrence across Norway during 2007–2017. Ptarmigan abundance was positively linked with rodent occurrence, consistent with the APH. Moreover, we found that the link between ptarmigan abundance and rodent dynamics was strongest in colder regions. Our study highlights how species interactions play an important role in population dynamics of species at high latitudes and suggests that they can become even more important in the most climatically harsh regions.

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