Winter foraging of sympatric red deer and sika deer in northeast China: diet composition, forage selection, bite diameter and browse intensity

Red deer (Cervus elaphus) and sika deer (C. nippon) are sympatric in certain regions in northeast China, and may have different strategies for obtaining food resources. We studied winter forage selection of sympatric red and sika deer based on their bite diameter and browse intensity in northeast China. The principal winter food items of red and sika deer were Euonymus spp. and Acer spp., and both deer showed strong selectivity for E. verrucosus, E. alatus and Populus davidiana (EI>0.85) in spite of their low availability. Red and sika deer exhibited varying bite diameters and browse intensity for different forage plant species between early and late winter. Overall, the interaction effect of season and deer species on bite diameter and browse intensity indicated that two sympatric deer used different foraging strategies to increase food intake. In late winter, sika deer may have tended to increase bite diameter to fulfill a relatively constant food intake and potential nutritional requirement, while red deer may have tended to increase browse intensity to maintain a higher forage intake. Moreover, the interaction effect of plant and deer species on bite diameter and browse intensity indicated that both deer species tend to change their bite diameter and browse intensity particularly on Euonymus spp. and Acer spp., while red and sika deer have a reversal interaction effect on coniferous browse. These patterns of forage selection in bite diameter and browse intensity of sympatric deer may reflect short-term foraging decisions of sympatric herbivores that share similar food resources.