Ecology and Genetic Identification of Alien Cervid in Jeju Island, South Korea

Abstract

This study investigated the ecology of alien sika deer on Jeju Island, with particular reference to their distribution, activity pattern, diet, and phylogeny using direct, indirect, and molecular analysis methods from Oct. 2018 – Dec. 2020. Research on the distribution range using direct and indirect survey methods identifies that the alien sika on Jeju Island have expanded their ranges towards the eastern and western parts of Hallasan National Park, taking into regard that they were initially released into the northern part. The southward expansion of their range has not yet been observed. This expansion into new ranges is driven by the availability of water, food, and climatic conditions. Sika deer were observed to prefer altitudes ranging from 550-1,100m, as this range is less preferred by native roe deer and has a less anthropogenic disturbance. Some illegal translocations, deliberate releases, or escapes of farmed individuals account for the increased deer population. Due to a lack of predatory or anthropogenic disturbance, the population will continue to increase beyond the current distribution range, hence a management strategy needs to be implemented. Results on activity patterns using camera traps revealed that sika deer were active throughout both day and night, but had activity peaks towards dawn and dusk. On the seasonal scales, they showed variation in their activity pattern (dawn and dusk in spring-autumn; day and night in winter) that could be linked to marked changes in temperatures and stress established by weather conditions. Sika deer displayed a higher to the lower extent of activity overlap with eight other species, including Siberian roe deer, red deer, wild boar, Asian badgers, Jeju weasels, domestic cattle, humans, and dogs. The native Siberian roe deer showed a higher incidence of activity overlap with sika deer in both summer and winter seasons, suggesting that the two ungulates had a common dietary preference. In contrast to summer, Jeju weasels and domestic cattle were not observed during winter seasons. In both of the seasons, activity overlap was lowest for humans and dogs. Higher activity overlap among morphologically different species causes conflicts, hence displacement of weak/small species cannot be negated. A proactive management strategy is recommended. Sika deer are dynamic in the procurement of food resources, as they fit into both the browsing and grazing categories. In this study, sika deer were found to consume 95 plant taxa of four categories (forb-climbers, graminoids, ferns and browse) using morphological and molecular analysis. Plant species belonging to the family Poaceae were consumed in a higher proportion. A higher number of dietary plants was found in summer (47 taxa) and lower in winter (27 taxa). Graminoids and forb-climbers primarily made up the spring and summer diets, whereas browse and ferns served as autumn and winter diets. This study revealed that the dietary preference of sika deer changes with the seasons. From the analysis of 21 tissue samples, five distinct groups of CytB haplotypes were identified, which clearly shows the presence of two haplotypes of sika deer (C. n. yakushimae and C. n. taiouanus), and three haplotypes of red deer (C. elaphus). Phylogenetic analysis showed that the sika deer subspecies C. n. yakushimae represents the mitochondrial lineage to Japanese sika deer, whereas C. n. taiouanus corresponds with a Taiwanese lineage. The red deer (C. elaphus) showed its lineage with Chinese, south-eastern Tibetan and western Sichuan populations. Through the analysis of the branching pattern of the maximum likelihood tree, no sequence mutations seem to have occurred. For the possible future hybridisation between sika with sympatric species, study should be carried out using nuclear genes. This study provides knowledge on the ecology of alien sika deer on Jeju Island. The finding suggests that integrative studies using advanced technology are highly recommended. Furthermore, an extensive survey using a large number of fecal samples and tissue samples from different locations and various individuals is required to confirm their distribution range and determine their evolutionary relationships, respectively.