Tannin Phenology is Associated with the Timing of Asiatic Black Bear Foraging among Persimmon Fruit Types

This study examined whether variation in tannin concentrations and tannin insolubilization timing among persimmon fruit types influences foraging frequency and seasonal timing in Asiatic black bears (Ursus thibetanus). Bear-constructed feeding platforms in persimmon trees served as fruit consumption indicators. The probability of platform formation was highest in pollination-constant nonastringent (PCNA) persimmons, intermediate in pollination-variant nonastringent (PVNA) fruit, and lower in pollination-variant astringent (PVA) and pollination-constant astringent (PCA) types. Platform formation timing followed a similar sequence, occurring earliest in PCNA, then PVNA, and subsequently PVA and PCA persimmons. Soluble phenolic content, a proxy for tannin concentration, was measured in fruit collected immediately after platform formation. Bear feeding platform formation was observed mainly at relatively low soluble phenolic levels, generally below approximately 0.5% fresh weight (FW) tannic acid equivalents (TAE). Generalized additive models describing seasonal changes in soluble phenolic concentrations indicated that concentrations were highest in PCA, followed by PVA, PVNA, and PCNA persimmons. The decline to low concentrations occurred earliest in PCNA and progressively later through PVNA, PVA, and PCA types. Overall, these findings suggest that soluble phenolic concentration and its seasonal dynamics may be associated with the temporal patterns of bear foraging on persimmon fruit.