Population dynamics and the role of protected areas in China's milu deer (Elaphurus davidianus) rewilding

Protected areas are refugia for wildlife and play a crucial role in biodiversity conservation, especially in the restoration of rare and endangered species. However, little attention has been paid to the long-term contribution of protected areas to rare species population rejuvenation. To identify the population growth of milu deer (Elaphurus davidianus)in protected areas and unprotected areas, we fitted the population dynamics curve of reintroduced free-ranging and wild populations based on long-term monitoring data in four protected areas: Jiangsu Dafeng Milu National Nature Reserve, Hubei Shishou Milu National Nature Reserve, Hunan East Dongting Lake National Nature Reserve, and Jiangxi Poyang Lake area. We also examined population dynamics in two unprotected areas: Yangbotan wetland and Sanheyuan wetland in Shishou County, Hubei province. We analyzed the habitat characteristics (coastal marshy wetland, riverine wetlands, and lake wetlands)in all these areas. The results showed that: (1) population growth in Dafeng, Shishou, Dongting, Sanheyuan and Yangbotan all followed an S-curve (p < 0.001); while population growth around Poyang Lake was linear (p < 0.001); (2) the population growth rate of Yangbotan wetland was significantly higher than that of Dongting Nature Reserve (p < 0.05); and (3) the two unprotected areas, Yangbotan and Sanheyuan wetlands, are important for the conservation of milu, as they have been facing the threats of urbanization and fragmentation in recent years. Our studies indicate that long-term conservation in protected areas has played an irreplaceable role in the reconstruction and rejuvenation of wild populations of milu deer over the past 30 years, and multiple reintroductions are an effective way to quickly restore wild milu populations in China.