Unveiling group dynamics and habitat utilization patterns of invasive sika deer (Cervus nippon) in Jeju Island, South Korea: Insights from camera trapping analysis

Invasive species pose significant threats to native ecosystems and species, especially on islands with high rates of endemism and susceptibility. The introduction of the sika deer (Cervus nippon) to South Korea has negatively impacted its wild ecosystems and native species, including those on Jeju Island. However, there is limited knowledge of sika deer ecology to inform effective species management and policy decisions. To bridge this knowledge gap, we examined the group dynamics, with a focus on age-sex class structure, group size, and habitat utilization variation of sika deer on Jeju Island, South Korea, by analyzing three years of camera trap data. Our findings illuminate a slightly skewed sex ratio toward females, with adults and yearlings comprising the dominant age class. The annual relative abundance of each age class showed a single activity peak in May for both yearlings and adults, whereas a peak was observed in August for juveniles. Group sizes ranged from to 1–7 individuals, with a mean group size of 3.72 ± 1.25 individuals. Habitat utilization patterns differed by age class, with juvenile abundance escalating with increasing distance from the forest edge, whereas adult females were active close to human settlements. This study highlights the critical importance of controlling the adult female population as a direct strategy for mitigating conflicts arising from sika deer habitat utilization. By addressing the unique behavior and habitat preferences of sika deer, our findings provide valuable insights for informed decision-making, effective species management, and preservation of native ecosystems, particularly on Jeju Island.