Past, present and future of the globally endangered Eld’s deer (Rucervus eldii) on Hainan Island, China

The Eld’s deer Rucervus eldii (Cervidae, Mammalia) is a tropical Asian deer restricted to dry lowland forests in the Indo-Burma Biodiversity Hotspot. Despite a historical range stretching across seven countries, all extant populations are small and highly fragmented, and the species is categorized as globally Endangered on the IUCN Red List of Threatened Species. The phylogeny and classification of the species is still debated and the population on China’s Hainan Island is currently widely regarded as an island population of R. e. siamensis, for which all populations are under immense threat of extinction. Unlike R. e. siamensis of Indochina, which has received little research attention since it was rediscovered in the wild in 1998, the Hainan Eld’s deer has been better studied with 91 scientific papers published, mostly in Chinese, on its taxonomy, population dynamics, biology and conservation. In this work, we (1) reviewed all scientific publications on Hainan Eld’s deer to provide an overview of its current research and conservation status, making this wealth of knowledge accessible to a wider scientific community, and (2) identify knowledge gaps and key research priorities to support effective conservation of the Hainan Eld’s deer. From over 40 years of research experience, it can be concluded that semi-wild population management in fenced protected areas is probably the most efficient short-term conservation strategy for this heavily hunted lowland species, but maintaining habitat quality in these enclosed reserves becomes the major challenge for conservation managers. Major knowledge gaps for the Hainan Eld’s deer include taxonomic status, recent trend in population dynamics, habitat selection and diet in a broader landscape. For the long-term survival of Hainan Eld’s deer, preserving and/or restoring suitable lowland habitats for reintroduction and curtaining poaching pressure are the keys.