Eremias argus, known as the Mongolian racerunner, is a reptile that has been designated as a level II endangered species in South Korea since 2005 despite being listed as “Least Concern” by the International Union for Conservation of Nature. Particular vegetation and soil characteristics are critical components of the habitat of E. argus, which is an ectotherm. However, research on the environmental characteristics of E. argus living on a fluvial island is lacking. This study sought to characterize the soil environmental factors and vegetation composition of E. argus habitats on Doriseom Island, South Korea by dividing the island into an area in which E. argus occurred frequently (F zone) and an area in which E. argus occurred rarely (R zone). Both soil hardness and cobble cover were significantly higher in the R zone (soil hardness: 1.6 ± 0.2 kg‧cm-2, mean ± standard error; cobble cover: 40 ± 5%) than in the F zone (soil hardness: 0.9 ± 0.1 kg‧cm-2; cobble cover: 18 ± 3%). Plant litter cover did not differ significantly based on E. argus occurrence. The vegetation composition within F and R zones appeared distinct, though Coreopsis lanceolata dominated both zones. A sand dune sedge, Carex pumila, thrived in F zone sites, where soil hardness was low, while the endemic Aster danyangensis, which prefers cobble areas, was found largely in the R zone. In conclusion, E. argus was most commonly found in areas with low soil hardness dominated by dune vegetation. Understanding endangered species’ habitat requirements can provide important clues for establishing conservation plans and restoration measures.
