Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Do Predators Limit the Abundance of Alternative Prey? Experiments with Vole-Eating Avian and Mammalian Predators

Kai Norrdahl and Erkki Korpimäki
Oikos
Vol. 91, No. 3 (Dec., 2000), pp. 528-540
Published by: Wiley on behalf of Nordic Society Oikos
Stable URL: http://www.jstor.org/stable/3547530
Page Count: 13
  • Read Online (Free)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Do Predators Limit the Abundance of Alternative Prey? Experiments with Vole-Eating Avian and Mammalian Predators
Preview not available

Abstract

Predation has been invoked as a factor synchronizing the population oscillations of sympatric prey species, either because predators kill prey unselectively (the Shared Predation Hypothesis; hereafter SPH), or because predators switch to alternative prey after a density decline in their main prey (the Alternative Prey Hypothesis; APH). A basic assumption of the APH is that the impact of predators on alternative prey depends more on the density of main prey than on the predator/alternative prey ratio. Both SPH and APH assume that the impact of predators on alternative prey is at least periodically strong enough to depress prey populations. To examine these assumptions, we utilized data from replicated field experiments in large areas where we reduced the breeding densities of avian predators during three years and the numbers of least weasels (Mustela nivalis) in two years when vole populations declined. In addition, we reduced the breeding densities of avian predators in two years when vole populations were high. The reduction of least weasels increased the abundance of their alternative prey, small birds breeding on the ground, but did not affect the abundance of common shrews (Sorex araneus). In years when vole populations declined, the reduction of avian predators increased the abundance of their alternative prey, common shrews and small birds. Therefore, vole-eating predators do at least periodically depress the abundance of their alternative prey. At high vole densities, the reduction of avian predators did not increase the abundance of common shrews, although the ratio of avian predators to alternative prey was similar to years when vole populations declined, which supported, APH. In contrast, the abundance of small birds increased after the reduction of avian predators also at high vole densities, which supported SPH. The manipulations had no obvious effect on the number of game birds, which are only occasionally killed by these small-sized predators. We conclude that in communities where most predators are small or specialize on a single prey type, the synchronizing impact of predation is restricted to a few similar-sized species.

Page Thumbnails

  • Thumbnail: Page 
528
    528
  • Thumbnail: Page 
529
    529
  • Thumbnail: Page 
530
    530
  • Thumbnail: Page 
531
    531
  • Thumbnail: Page 
532
    532
  • Thumbnail: Page 
533
    533
  • Thumbnail: Page 
534
    534
  • Thumbnail: Page 
535
    535
  • Thumbnail: Page 
536
    536
  • Thumbnail: Page 
537
    537
  • Thumbnail: Page 
538
    538
  • Thumbnail: Page 
539
    539
  • Thumbnail: Page 
540
    540