Rodent population cycles: life history adjustments to age-specific dispersal strategies and intrinsic time lags.

Multi-annual population cycles can be generated by life history responses to density dependent changes in adult and pre-reproductive survival. The proximate mechanism linking population dynamics and demography of cycling rodents appears to be high pre-reproductive dispersal at peak density, or during periods of population increase. This model is similar to the Chitty hypothesis which can best be viewed as a special case of demographic control on population size. Normally, this control should be selfreinforcing and lead to damped oscillations toward a stable population density. Intrinsic time lags induced by variation in the length of the breeding season modify the dependence of demography on population size, and enable the cycles to persist.