Overlap in habitat use and activity patterns between sika deer (Cervus nippon) and Japanese serows (Capricornis crispus) in subalpine habitats: exploitative competition rather than direct interference?

Examining multiple niche relationships, such as habitat use and activity patterns, between sympatric species contributes to an understanding of the mechanisms of coexistence and competition. Sika deer (Cervus nippon Temminck, 1838) and Japanese serows (Capricornis crispus (Temminck, 1836)) often show different habitat use, and diversity in vegetation and topography seems to facilitate their coexistence. Conversely, their habitat use may overlap in areas with low-diversity habitats; however, this remains unstudied. Moreover, whether they spatiotemporally avoid each other to reduce direct interference is unclear. We examined the fine-scale patterns of habitat use and activity of deer and serows in the subalpine forests of Mount Fuji, which have low-diversity habitats, using camera trapping data over 3 years. Deer and serow habitat niches largely overlapped, especially in summer (92%–94%) and autumn (89%–91%), suggesting that low-diversity habitats facilitate overlapping habitat use. Both species selected areas frequently used by the other during spring to autumn and their temporal niches largely overlapped, especially in summer (88%) and autumn (83%), suggesting that they do not spatiotemporally avoid each other (i.e., there is no direct interference). Rapid range expansion of deer into these subalpine habitats may exclude native serows through resource exploitative competition rather than interference competition.