Large prey for small cubs ‐ on crucial resources of a boreal red fox population

Many studies of red fox Vulpes vulpes diet have indicated a higher frequency of large prey in the diet of cubs at dens in relation to that of adults From time to time this finding has been questioned as an artifact due to the different types of sampling In this paper I suggest that the observations were correct and reflected optimal behaviour of a central place forager I compared the diet of foxes by analyses of 112 cub scats collected at breeding dens and 168 adult scats collected during the same periods The study was performed in a boreal environment, characterised by cyclically fluctuating vole populations According to theory the diets should converge when voles become plentiful During a year of low, but increasing, vole densities, a significantly higher proportion of large prey was found in the sample from cubs than from adults This was not the case during the peak and the decline year, when the presumably easily available voles appeared frequently in the scats of both cubs and adults I argue that the availability of large prey during the first year of increasing vole densities might determine territory sue and hence also average population density of foxes throughout the whole cycle in boreal foxes