Influence of geographical scale on the detection of density dependence in the host-parasite system, Arvicola terrestris and Taenia taeniaeformis
Résumé
Infection by the cestode Taenia taeniaeformis was investigated within numerous cyclic populations of the fossorial water vole Arvicola terrestris sampled during 4 years in Franche-Comte´ (France). The relative in.uence of di.erent rodent demographic parameters on the presence of this cestode was assessed by considering (1) the demographic phase of the cycle; (2) density at the local geographical scale (<0.1 km2) ; (3) mean density at a larger scale (>10 km2). The local scale corresponded to the rodent population (intermediate host), while the large scale corresponded to the de.nitive host population (wild and feral cats). General linear models based on analyses of 1804 voles revealed the importance of local density but also of year, rodent age, season and interactions between year and season and between age and season. Prevalence was signi.cantly higher in low vole densities than during local outbreaks. By contrast, the large geographical scale density and the demographic phase had less in.uence on infection by the cestode. The potential impacts of the cestode on the .tness of the host were assessed and infection had no e.ect on the host body mass, litter size or sexual activity of voles