Could Conservation Strategies for the Hainan Gibbon Generate an Umbrella Effect for the Hainan Four-eyed Turtle?

Umbrella species can facilitate efficient biodiversity conservation, as their targeted protection effectively safeguards co-occurring species and entire ecosystems in conservation management. To verify Hainan gibbon (Nomascus hainanus) as an umbrella species for sympatric endangered species, this study evaluated the conservation efficacy of the Hainan four-eyed turtle (Sacalia insulensis) through multidimensional spatiotemporal analysis. By comparing the population data collected using cage-trapping methods from 2005 to 2025, the S. insulensis population in the Bawangling region of the Hainan Tropical Rainforest National Park has exhibited obvious recovery, from no initial records to 25 individuals (mean relative population density: 0.0404 individuals/cage-day). Its growth trajectory is closely linked to the continuous enhancement of conservation efforts for Hainan gibbons, confirming umbrella effects stemming from poaching suppression and habitat restoration. However, when compared with recent surveys in other park regions, significant spatial limitations were revealed that the mean relative population densities at Yinggeling (0.01 individuals/cage-day) and Diaoluoshan (0.0064 individuals/cage-day) were only 25.74% and 15.84%, respectively. Additionally, juveniles constituted only 12% of Bawangling's population, indicating that while the umbrella strategy delivers meaningful conservation outcomes, supplementary targeted initiatives are still needed to improve efficiency in resolving the species reproductive bottlenecks (e.g., nesting habitat quality). Those findings demonstrate that umbrella species conservation can establish an ecological conservation force field; however, its effectiveness is constrained by unequal resource allocation and species niche differences. Future efforts should overcome the spatial and ecological limitations of single-species umbrella effects by using smart patrol networks, secondary umbrella species mechanisms, and dedicated management plans.