Ecological drivers of population abundance of the Japanese serow in the absence of predation risk

Abstract In ungulates, population abundance is mainly influenced by forage condition, predation pressure, competitor abundances, and human activities; however, information about the effect of the escape terrain on the population abundance is still scarce. Some ungulate species often use areas with abundant escape terrain despite the absence of predators, indicating that the ghosts of predators past continue to affect their spatial behavior, and population abundance of such ungulates may also be influenced by the escape terrain. We examined population abundance of the Japanese serow ( Capricornis crispus ) in Mt. Fuji and its surrounding mountains with the absence of predators, including both natural and human hunters, in relation to forage condition, vegetation, escape terrain (steep slopes), potential competitor (sika deer Cervus nippon ), and non-invasive human activities. The population abundance (pellet group numbers) of serows was higher in coniferous forests than in broad-leaved forests, and in areas with abundant dwarf bamboos and where high fecal nitrogen content was detected, suggesting that forage availability of dwarf bamboo and coniferous trees as well as forage quality influenced their abundance. Conversely, sika deer abundance and human residences did not affect the population abundance of serows, suggesting that the potential competitor and the non-invasive human activity may not have had a direct effect on the serow abundances. Moreover, the population abundance of serow was higher in areas with abundant escape terrain, suggesting that the ghosts of predators past may affect their abundance. Population abundance of serows may be low in areas with scarce escape terrains because fewer individuals settle in environments with minimal escape terrain.