Demography of a carnivore, the red fox, Vulpes vulpes,: what have we learnt from 70 years of published studies?

Abstract

Populations of the same species often face different selection pressures and, increasingly, the demography of populations within a species has been shown to be highly variable. Knowledge of such intraspecific differences has implications for substituting demographic data, a practice that is often necessary for population modelling due to missing parameters. The red fox Vulpes vulpes, a widely-studied, widespread and economically important species, offers an opportunity to consider the degree of intraspecific variability in the demography of a carnivore and to test the consequences of interpopulation data substitution. We use published life history data to review the extent and quality of demographic data for fox populations. Using demographic descriptors, matrix models, and perturbation analyses, we identify important demographic properties and classify interpopulation variation along the fast-slow continuum. We also illustrate the consequences of data substitution in demographic models. Data quality varies substantially between reviewed studies. Sufficient data exist to model the demography of eight of 56 study populations. Modelled populations have a tendency towards positive population growth, with survival and fecundity of the youngest age class contributing most to that growth. Metrics point to strategies ranging from medium to fast life histories. While broad demographic similarities exist among fox populations, our results imply considerable demographic variation between populations. We show that significant differences in model outcomes based on substituted data are dependent on the parameter replaced, and that geographic proximity does not imply demographic similarity. Superficially, the red fox appears to have been well studied, yet there are remarkably few usable demographic data from much of its range. Despite 70 years of published studies, we were unable to examine the effects on demographic parameters of harvesting regimes, density and weather. We propose improvements to enhance the value of demographic data, both for foxes and for other species.