Ghosts of predators past remain in the spatial distribution and population density of the Japanese serow

Abstract

Some ungulate species select areas with abundant escape terrain despite the absence of predators, indicating that the ghosts of predators past continue to affect their spatial behavior. Population densities of such ungulates may also be influenced by the escape terrain; however, this has not been fully investigated. We examined spatial distribution and population density of the Japanese serow (Capricornis crispus) at Mt. Fuji in the absence of predators in relation to abundance and quality of forage, vegetation, escape terrain (steep slopes), and other factors. Only escape terrain affected serow spatial distribution and their distribution was biased towards areas with steeper slopes, suggesting that the ghosts of predators past, i.e., wolves (Canis lupus) and serow-hunting humans, still influence serow spatial distribution. The population density 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 population density. Moreover, the population density of serows was higher in areas with abundant escape terrain, suggesting that the ghosts of predators past still affect their population density. Population densities of serows may be low because fewer individuals settle in environments with minimal escape terrain.