The milu deer (Elaphurus davidianus), a National First-Class Protected Animal in China, serves as a flagship species for the Yangtze River ecosystem. As a unique cervid species endemic to China, it originated approximately 2 to 3 million years ago during the Early Pleistocene. Thriving on grasses and aquatic vegetation, these deer inhabit marshy wetlands and were once widely distributed across the warm, humid regions of the Yellow and Yangtze River basins.

Known as the "Four-Not-Like" (Si Bu Xiang) due to its distinctive features—resembling a horse's face, a deer's antlers, a cow's hooves, and a donkey's tail—the milu deer holds mythical significance in Chinese culture. In the classic novel The Investiture of the Gods(Fengshen Yanyi), it is depicted as Jiang Ziya's divine steed, further cementing its legendary status.
Over the past three decades, the Shishou Milu Nature Reserve has achieved remarkable success. The population has grown to over 4,500 individuals, with 2,901 residing within the reserve and 1,600+ naturally dispersing to areas like Sanheyan, Yangbotan, and Dongting Lake. This expansion has established the largest wild milu deer population globally, spanning two provinces and nine counties along the Yangtze and Dongting Lake basins. Recognized by UNESCO as a "successful model in global endangered species conservation," this initiative has become a shining example of Hubei Province's commitment to the Yangtze River's ecological protection.