Selective bark-gnawing of Formosan squirrels in relation to the herbivore-repellent components of broad-leaved trees

Abstract

Bark gnawing by Formosan squirrels has been observed in forests around Yokohama City, Kanagawa Prefecture. Chemical components may be key features for squirrels in choosing target trees. In the present study, the amounts of polyphenols, resins, and flavanols, which are assumed to act as repellent to Formosan squirrels, were compared among nine tree species dominated in this area. The samples were collected and analyzed individually through four different seasons. The results suggested that the amounts of these three components were constant to each species and did not show apparent seasonal variations in most species. Trees of hurt species (e.g., Machilus thunbergii and Neolitsea sericea) included lower percentage of three components, while those of non-hurt species (e.g., Quercus serrata and Prunus jamasakura) showed higher concentration in some of them.