STABLE ISOTOPIC EVIDENCE FOR DIETS AND NICHE DIFFERENTIATION OF EARLY PLEISTOCENE PANDA AND ASSOCIATED MAMMALS FROM YANLIANG CAVE, SOUTH CHINA

To better understand the dietary evolution and habitat change of panda, this study analyzed stable isotopes of carbon and oxygen in tooth enamel samples from two pygmy pandas and associated mammals from Yanliang Cave (early Pleistocene) in the Chongzuo Ecological Park of Guangxi Province in South China. The results show that the pygmy panda, Ailuropod microta, had the lowest enamel-δ¹³C values compared to other coexisting mammals, suggesting that the pygmy panda had a pure C3 diet composed of plants growing in the understory of a closed-canopy forest. A pure C3 diet for the pygmy panda, if confirmed by more data, would be consistent with an already established dietary niche of bamboo (a C3 plant). Reconstructed δ¹³C values of diets for the Yanliang fauna range from -25.6 to -32.1‰, indicating that these early Pleistocene mammals ate predominantly C3 vegetation and lived in an environment dominated by C3 plants. This suggests that the area was comprised of wooded habitats ranging from closed canopy forests to woodlands. Significant intra-tooth δ¹³C variations observed in some grazing animals suggest that a small amount of C4 grasses may be present in patches of open areas in a predominantly forested landscape. The reconstructed δ¹⁸O values of meteoric water in the area during the early Pleistocene fall within the range of -7.6 to -7.8‰, lower than the present-day mean annual precipitation δ¹⁸O values in the region, suggesting a wetter climate or stronger monsoon season in the early Pleistocene than today.