title: Surviving winter: Food, but not habitat structure, prevents crashes in cyclic vole populations.
abstract: Vole population cycles are a major force driving boreal ecosystem dynamics in northwestern Eurasia. However, our understanding of the impact of winter on these cycles is increasingly uncertain, especially because climate change is affecting snow predictability, quality, and abundance. We examined the role of winter weather and snow conditions, the lack of suitable habitat structure during freeze-thaw periods, and the lack of sufficient food as potential causes for winter population crashes. We live-trapped bank volesMyodes glareoluson 26 plots (0.36 ha each) at two different elevations (representing different winter conditions) in southeast Norway in the winters 2013/2014 and 2014/2015. We carried out two manipulations: supplementing six plots with food to eliminate food limitation and six plots with straw to improve habitat structure and limit the effect of icing in the subnivean space. In the first winter, all bank voles survived well on all plots, whereas in the second winter voles on almost all plots went extinct except for those receiving supplemental food. Survival was highest on the feeding treatment in both winters, whereas improving habitat structure had no effect. We conclude that food limitation was a key factor in causing winter population crashes.
authors.affiliation: Faculty of Applied Ecology and Agricultural Science Hedmark University of Applied Sciences Koppang Norway.
authors.forename: Kaja
authors.initials: K
authors.lastname: Johnsen
authors.affiliation: Department of Biological Sciences University of Toronto Scarborough Toronto ON Canada.
authors.forename: Rudy
authors.initials: R
authors.lastname: Boonstra
authors.affiliation: Department of Biological Sciences University of Alberta Edmonton AB Canada.
authors.forename: Stan
authors.initials: S
authors.lastname: Boutin
authors.affiliation: Faculty of Applied Ecology and Agricultural Science Hedmark University of Applied Sciences Koppang Norway.
authors.forename: Olivier
authors.initials: O
authors.lastname: Devineau
authors.affiliation: Department of Zoology University of British Columbia Vancouver BC Canada.
authors.forename: Charles J
authors.initials: CJ
authors.lastname: Krebs
authors.affiliation: Faculty of Applied Ecology and Agricultural Science Hedmark University of Applied Sciences Koppang Norway.
authors.forename: Harry P
authors.initials: HP
authors.lastname: Andreassen
keywords: climate; feeding experiment; habitat quality; population dynamics; rodents