Summer food composition and food niche overlap of the raccoon dog, red fox and badger in Finland

Diets of raccoon dog, red fox and badger were studied in southern Finland from 1990 to 1996 by collecting faeces from dens and latrines during May-July of each year. The frequency of occurrence and relative volume of each food item in the faeces were calculated. The raccoon dog was the most and the red fox the least omnivorous of these carnivores, according to the diversity index. Diet composition of all these species varied among areas, indicating that they are opportunistic feeders. Mammals and birds constituted the bulk of the fox diet, while invertebrates, frogs and plants were most frequently eaten by the badger. The frequency of earthworms in badger faeces varied between 16 and 77%, according to area. Voles and shrews were important to the raccoon dog, but it also frequently consumed other food items. The food niches of the badger and the raccoon dog overlapped more than that of the red fox and other species. The red fox was more carnivorous and fed on larger prey items than the others, but the food composition of the red fox in the present study reflects the prey carried to the den for the pups; thus, the diet of adult foxes may be more similar to that of the raccoon dog. In conclusion, these 3 carnivores share many resources, suggesting that competition may occur among them: however, their diets also differ to some extent, which helps them to avoid competition. Furthermore, the badger and the raccoon dog are dormant during winter, when food is scarcest, which may be the reason why all these species can coexist in rather unproductive boreal forests.