Invading parasites cause a structural shift in red fox dynamics

The influence of parasites on host life histories and populations is pronou nced. Among several diseases affecting animal populations throughout the wo rld, sarcoptic mange has influenced many carnivore populations dramatically and during the latest epizootic in Fennoscandia reduced the abundance of r ed fox by over 70%. While the numerical responses of red fox populations, t heir prey and their competitors as well as clinical implications are well k nown, knowledge of how sarcoptic mange affects the structure of the dynamic s of red fox populations is lacking. Integrating ecological theory and stat istical modelling, we analysed the long-term dynamics (1955-1996) of 14 Dan ish red fox populations. As suggested by the model, invading sarcoptic mang e significantly affected direct and delayed density dependence in red fox d ynamics and concomitant shifts in fluctuation patterns were observed. Our s tatistical analyses also revealed that the spatial progressive spread of ma nge mites was mirrored in the autocovariate structures of red fox populatio ns progressively exposed to sarcoptic mange.