Abundance and Morphology of Japanese Mulberry Trees in Response to the Distribution of Japanese Macaques in Snowy Areas

Abstract

One of the rare documented cases of an antagonistic primate-plant interaction is selective foraging by Japanese macaques (Macaca fuscata) on the bark or buds of Japanese mulberry trees (Morus bombycis) in cool-temperate forests. We examined how this selective foraging behavior influences the growth and development of mulberry trees in a large geographic space with different environmental conditions by selecting study areas in northern Japan. We found that the foraging caused potentially fatal damage to 5%-10% of the mulberry trees and led to dwarfing of the tree morphology. However, the stem density of the monitored mulberry trees was the highest in the area with a long history of occupancy by macaque groups; moreover, the foraging commonly resulted in compensatory plant growth by increasing shoot number. These findings indicate that the macaque-mulberry relationship is not always antagonistic. Sufficient snow cover could be a key environmental factor to establish this non-antagonistic interaction by suppressing the negative influence of macaques as a destructive herbivore and improving their positive influence as a skilful gardener. Finally, we performed decision tree modeling based on the J48 algorithm to investigate geographic variation in mulberry abundance and morphology in response to the distribution of macaques. We developed an explicit tree model with reasonable predictive performance that not only enables a better understanding of primate-plant interactions but also provides information regarding the time of occupancy by Japanese macaques in a given area based on the abundance and morphology of mulberry trees. This result indicated that the observation of preferred tree species could be an indirect measure that reliably indexes macaque habitat use. © 2010 Springer Science+Business Media, LLC.