The beneficial role of plant secondary compounds in giant panda foraging ecology

Abstract

Forage selection by mammalian herbivores has shown to be influenced by plant nutritional content, but the role of plant secondary compounds (PSCs) on forage selection is less well understood. Here, we studied the role of PSCs in giant panda (Ailuropoda melanoleuca) foraging strategies; examined seasonal and age class variation in PSC composition in the panda’s principal food resource, bamboo (Bashania fargesii); evaluated anti-oxidant and antibacterial effects of bamboo extract; and determined how panda’s seasonal movements and foraging patch selection which were determined by GPS collars related to patterns of PSC concentrations in bamboo. Panda’s selection of foraging sites indicated positive selection for several PSCs, including flavonoids, alkaloids, and tannins. Pandas primarily ingested bamboo leaves, as opposed other parts of the bamboo, during the time of year when many PSC concentrations were at their highest. Further, pandas prefer to forage on younger bamboo, which contains higher concentrations of alkaloids and antibacterial activity than older bamboo. As might be expected for compounds that can have positive or negative biological effects depending on dose, pandas appeared to select both for and against some PSCs depending on context. Ex situ experiments showed that flavonoids and alkaloids were influential antioxidants and tannins and alkaloids had high levels of antibacterial activity. Panda foraging sites were characterized by high anti-oxidant activity. Variation in PSC content of bamboo on the landscape may have profound effects on pandas, including parasite control, protecting against cancer, improved cardiovascular health, and disease prevention. These potential roles of PSCs should receive greater attention in ecology and conservation.