Density-dependent reproduction causes winter crashes in a common vole population
Résumé
Common voles in western France exhibit threeyear
population cycles with winter crashes after large
outbreaks. During the winter of 2011–2012, we monitored
survival, reproduction, recruitment and population growth
rate of common voles at different densities (from low to
outbreak densities) in natura to better understand density
dependence of demographic parameters. Between October
and April, the number of animals decreased irrespective of
initial density. However, the decline was more pronounced
when October density was higher (loss of &54 % of
individuals at low density and 95 % at high density). Using
capture-mark-recapture models with Pradel’s temporal
symmetry approach, we found a negative effect of density
on recruitment and reproduction. In contrast, density had a
slightly positive effect on survival indicating that mortality
did not drive the steeper declines in animal numbers at high
density. We discuss these results in a population cycle
framework, and suggest that crashes after outbreaks could
reflect negative effects of density dependence on reproduction
rather than changes in mortality rates.