Yan Shu, Fengmei Wang, Jinchao Tan, Dapeng Zhu, Leigang Zhao, Tingting Fang, Shibin Yuan, Le Wang
The giant panda (Ailuropoda melanoleuca) is an obligate bamboo specialist and exhibits pronounced seasonal shifts in diet composition. To investigate how wild pandas respond to seasonal variations in dietary trace minerals, we quantified four essential elements-iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu)-in the dominant bamboo species (Bashania fargesii and Fargesia qinlingensis) and in panda feces over a full annual cycle in Foping National Nature Reserve, China. Using nutritional geometry (Geometric Framework, GF) and the Right-Angled Mixture Triangle (RMT) model, we assessed seasonal intake priorities, key elemental ratios (Cu/Mn, Cu/Zn), and relative mineral utilization. Trace mineral prioritization was strongly time-dependent: during the breeding, leaf-feeding, and overwintering periods, the prioritization pattern was Cu > Zn > Mn, whereas during the shoot-feeding stages of both bamboo species, it shifted to Cu > Mn > Zn. Copper consistently emerged as the highest ingestion priority mineral across all seasons, while iron consistently showed the lowest ingestion priority. The Cu/Mn and Cu/Zn ratios varied dynamically with dietary shifts: Cu/Mn was significantly higher in shoots than in leaves, and Cu/Zn peaked in April (Bashania shoots) and August (Fargesia leaves). Compared with wild individuals, captive pandas in Sichuan exhibited substantially higher Fe intake relative to Cu (77-623 mg Fe per 1 mg Cu vs. 13-29 mg Fe per 1 mg Cu in wild pandas), indicating a potential risk of iron overload. We conclude that wild giant pandas maintain trace mineral balance by synchronizing seasonal migration and dietary switching with fluctuations in bamboo mineral profiles. Our results emphasize the conservation importance of maintaining bamboo diversity in situ and highlight the need to refine captive feeding protocols to mimic wild seasonal nutritional patterns, particularly with respect to Fe regulation.