Favorite Parts of a Single Leaf for Giant Flying Squirrels to Eat in Three Species of Food Trees

To examine the effect of leaf chemical composition on selective herbivory by the Japanese giant flying squirrels (Petaurista leucogenys), we measured and compared the total phenolic, glucose, and water contents of leaves among their main food tree species, deciduous Quercus acutissima, and evergreen Q. sessilifolia and Phonitia serratifolia. Leaves of these three tree species were available in the warm season (April to October), but the flying squirrels mostly preferred the leaves of Q. acutissima, having higher glucose and water contents than those of the other two tree species. In the cold season (November to the next March), the two evergreen tree species were available, and the flying squirrels used both leaves without any apparent influence of the chemical compositions. On the other hand, the favorite parts of a single leaf differed among the three tree species. Flying squirrels dropped the individual leaves after partial consumption. Their feeding marks on the dropped leaves were distinguished into four types: apical, basal, central, and marginal parts of consumption. The basal parts of consumption were most frequent in Q. acutissima leaves in which more water was contained at the basal part, and the central part consumption followed, which may be related to a lower phenolic content and more glucose and water at the leaf center than its margin. In contrast, the apically consumed leaves dominated in Q. sessilifolia, with relatively homogeneous leaf chemical distribution except for more water at the center. In P. serratifolia, leaves consumed at the center were frequent, but those with marginal consumption were also observed, which may be related to its specific chemical distribution with less phenolics and more glucose at the leaf margin. Thus, the chemical distributions within the single leaf differ among tree species, and the flying squirrel’s selectivity of the tree species and the part of each leaf depends partly on the relative compositions of preferable glucose and water and unpreferable phenolics.