Space as the potential limiting resource in the competition between the Japanese serow and the sika deer in Ashio, central Japan

Abstract

The reasons for the competitive exclusion of the Japanese serow Capricornis crispus by the sika deer Cervus nippon in the Ashio Mountains, central Japan, were studied. The study comprised an analysis of encounters between individuals of these two sympatric species, and the demographic structure of the serow population. Serows tended to avoid deer (X² = 29.23, df = 2, p < 0.001), whereas sika deer seemed to ignore the presence of serows (X² = 0.87, df = 2, p = 0.647). The serow population showed clear signs of ageing; the proportion of juvenile animals was very low. The results suggest that behavioural interactions play an important role in the interspecific competition between the two species in Ashio. There is little evidence for trophic competition between the two species. This conclusion is supported by a review of the available literature on the food niche overlap between the Japanese serow and the sika deer. Other possible explanations for the serow population decline in Ashio, such as habitat changes, loss of genetic variability, and diseases, were concluded to be not relevant.