title: Dampening prey cycle overrides the impact of climate change on predator population dynamics: a long-term demographic study on tawny owls.
abstract: Predicting the dynamics of animal populations with different life histories requires careful understanding of demographic responses to multifaceted aspects of global changes, such as climate and trophic interactions. Continent-scale dampening of vole population cycles, keystone herbivores in many ecosystems, has been recently documented across Europe. However, its impact on guilds of vole-eating predators remains unknown. To quantify this impact, we used a 27-year study of an avian predator (tawny owl) and its main prey (field vole) collected in Kielder Forest (UK) where vole dynamics shifted from a high- to a low-amplitude fluctuation regime in the mid-1990s. We measured the functional responses of four demographic rates to changes in prey dynamics and winter climate, characterized by wintertime North Atlantic Oscillation (wNAO). First-year and adult survival were positively affected by vole density in autumn but relatively insensitive to wNAO. The probability of breeding and number of fledglings were higher in years with high spring vole densities and negative wNAO (i.e. colder and drier winters). These functional responses were incorporated into a stochastic population model. The size of the predator population was projected under scenarios combining prey dynamics and winter climate to test whether climate buffers or alternatively magnifies the impact of changes in prey dynamics. We found the observed dampening vole cycles, characterized by low spring densities, drastically reduced the breeding probability of predators. Our results illustrate that (i) change in trophic interactions can override direct climate change effect; and (ii) the demographic resilience entailed by longevity and the occurrence of a floater stage may be insufficient to buffer hypothesized environmental changes. Ultimately, dampened prey cycles would drive our owl local population towards extinction, with winter climate regimes only altering persistence time. These results suggest that other vole-eating predators are likely to be threatened by dampening vole cycles throughout Europe.
authors.affiliation: Institut Méditerranéen de Biodiversité et d'Ecologie marine et continentale (IMBE), Aix-Marseille Université, UMR CNRS IRD Avignon Université, Technopôle Arbois-Méditerranée Bât. Villemin - BP 80, Aix-en-Provence Cedex 04, F-13545, France; School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Zoology Building, University of Aberdeen, Aberdeen, AB24 2TZ, UK.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Millon
authors.forename: Steve J
authors.initials: SJ
authors.lastname: Petty
authors.forename: Brian
authors.initials: B
authors.lastname: Little
authors.forename: Olivier
authors.initials: O
authors.lastname: Gimenez
authors.forename: Thomas
authors.initials: T
authors.lastname: Cornulier
authors.forename: Xavier
authors.initials: X
authors.lastname: Lambin
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000502:physiology*; D057231:Climate Change; D004739:England; D005260:Female; D020387:Food Chain; D008297:Male; D008954:Models, Biological; D011157:Population Dynamics; D012621:Seasons; D020305:Strigiformes / Q000502:physiology*
keywords: North Atlantic oscillation; demographic rates; functional response; population viability analysis; prey cycle; stochastic population dynamics; trophic interactions