Abstract
The prey preference of the red fox on small rodents was studied by faecal analysis of foxes and a census of rodents in Hokkaido, Japan. The study area included the home ranges of two fox families which were dtermined by tracking in the snow. The number of foxes, a maximum of twelve and a minimum of three, varied depending on the season. It appeared that, from the census of small rodents, Clethrionomys rufocanus was dominat and mice of the genus Apodemus were also fairly abundant in teh study area. A total of 941 faecal sample of the foxes were analyzed and it was indicated that C. rufocanus constituted a very high percentage of the consumed rodents. Ivlev's index was calculated from the percentage of dry matter of each species in the feces and the biomass of each in the study area. It was suggested that the red foxes preferred C. rufocanus to genus Apodemus. The factors afecting prey preference were discussed on the basis of the relationships between the habitats of foxes and prey rodents.
