EN
Geographical variation in the diet of sika deer Cervus nippon Temminck, 1838 has been well characterised: northern populations are grazers, whereas southern deer are browsers. This variation largely reflects genetic-based differences in morphology. However, environmental factors would be also important. If a same genetic population live in different habitats, we can check altitudinal shifts in sika deer food consumption. We hypothesised that changes in the diet of the sika deer population on the Izu Peninsula, which is located within the transitional zone of resource (vegetation) variation and encompasses a broad altitudinal range, would mirror shifts in the composition of vegetation. Analyses of the rumen contents of the deer population indicated that dwarf bamboo accounted for 10.5, 46.2, and 74.3% of the deer diet in the low (<800 m), middle (800–1000 m), and high (>1000 m) altitudinal zones, respectively. In contrast, evergreen broad-leaved species accounted for 35.7, 23.1, and 5.9%, respectively. These results suggest that the diet of sika deer is more strongly affected by environmental factors, such as plant community composition, than by genetic factors.