Modelling Fine-scale Habitat Suitability and Connectivity of an Invasive Species, Sika Deer on Jeju Island, South Korea

Invasive species pose threats to island ecosystems by disrupting native biodiversity, altering habitats, and increasing human-wildlife conflicts. The sika deer (Cervus nippon); an invasive species on Jeju Island, South Korea, has expanded in range, raising ecological and agricultural concerns. Fine-scale environmental variables play a critical role in determining habitat suitability and connectivity, thereby influencing the spread and impact of invasive species. This study assessed the fine-scale habitat suitability and connectivity of sika deer by analyzing eco-geographical variables using the optimized maximum Entropy (MaxEnt) model and linkage mapper, respectively. After a multicollinearity test, 97 occurrence records were coupled with 12 environmental variables for the final projection. The model demonstrated excellent predictive performance with the Area Under the Receiver Operating characteristic Curve (AUC) and True Skill Statistics (TSS), and Continuous Boyce Index (CBI) yielding scores of 0.88 ± 0.03, 0.68 ± 0.02, and 0.82 +0.05, respectively. The distance to Oreum (volcanic cone), forest, and agricultural landscapes were identified as the strongest predictors of sika deer distribution. The model predicted that 5.79 % of Jeju Island was a highly suitable habitat and 4.92% was suitable, suggesting significant potential for range expansion and increased human-deer conflicts. Thirteen core habitats across the landscape were identified, connected by 26 least-cost paths. A centrally located core habitat; Chetmang oreum area was identified as the most important habitat for maintaining overall connectivity. In conclusion, the study findings highlight the need for targeted monitoring and management, particularly in grassland and agricultural landscapes where deer presence may threaten native vegetation and crops.