Meadow vole cycles within fences

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Abstract
To test the idea that dispersal is necessary for cycling and to develop an enclosure that would permit vole population cycling, we partially and fully fenced grids that included woodland areas (dispersal sinks) that were continually trapped out. We studied three populations of the meadow vole, Microtus pennsylvanicus, in Massachusetts from 1978 to 1982. The control population and both fenced populations exhibited virtually identical demographic trends, which encompassed a vole cycle. Analysis of demographic parameters suggested that the major effect of the fence was to increase survival within. We attributed this increased survival to reduced dispersal because a dispersal sink attracted only 98 dispersers throughout the study, We suggest that there is a continuum of individual thresholds to disperse with only a very few animals motivated enough to enter a woodland dispersal sink.