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Predator-mediated interactions between preferred, alternative and incidental prey in the arctic tundra

Authors

  • Laura Mckinnon,

    1. Chaire de Recherche du Canada en Conservation des Écosystèmes Nordiques and Centre d’Études Nordiques, Univ. du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada.
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  • Dominique Berteaux,

    1. Chaire de Recherche du Canada en Conservation des Écosystèmes Nordiques and Centre d’Études Nordiques, Univ. du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada.
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  • Gilles Gauthier,

    1. Chaire de Recherche du Canada en Conservation des Écosystèmes Nordiques and Centre d’Études Nordiques, Univ. du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada.
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  • Joël Bêty

    1. Chaire de Recherche du Canada en Conservation des Écosystèmes Nordiques and Centre d’Études Nordiques, Univ. du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada.
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L. McKinnon, Chaire de Recherche du Canada en Conservation des Écosystèmes Nordiques and Centre d’Études Nordiques, Univ. du Québec à Rimouski, 300 Allée des Ursulines, Rimouski, Québec, G5L 3A1, Canada. E-mail: laura.mckinnon3@gmail.com

Abstract

Apparent competition between prey is hypothesized to occur more frequently in environments with low densities of preferred prey, where predators are forced to forage for multiple prey items. In the arctic tundra, numerical and functional responses of predators to preferred prey (lemmings) affect the predation pressure on alternative prey (goose eggs) and predators aggregate in areas of high alternative prey density. Therefore, we hypothesized that predation risk on incidental prey (shorebird eggs) would increase in patches of high goose nest density when lemmings were scarce. To test this hypothesis, we measured predation risk on artificial shorebird nests in quadrats varying in goose nest density on Bylot Island (Nunavut, Canada) across three summers with variable lemming abundance. Predation risk on artificial shorebird nests was positively related to goose nest density, and this relationship was strongest at low lemming abundance when predation risk increased by 600% as goose nest density increased from 0 to 12 nests ha−1. Camera monitoring showed that activity of arctic foxes, the most important predator, increased with goose nest density. Our data support our incidental prey hypothesis; when preferred prey decrease in abundance, predator mediated apparent competition via aggregative response occurs between the alternative and incidental prey items.

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