The Eurasian otter (Lutra lutra) is an endangered species for which diet analyses are needed as part of its conservation efforts. Eurasian otters feed on vertebrates, such as fishes, and invertebrates, such as crustaceans, but their detailed taxonomies are not fully understood in part due to limited resolving power of traditional morphological identification methods. Here, we used high-throughput sequencing (HTS)-based DNA metabarcoding approaches to analyze diet profiles of Eurasian otters inhabiting a marshy estuary area in Korea. We investigated their diet profiles based on spraint sampling followed by DNA metabarcoding analyses targeting 12S rRNA gene region for vertebrates, 16S rRNA gene region for invertebrates, and cytochrome c oxidase 1 (COI) gene region for fishes. For the vertebrate analysis, a blocking oligonucleotide (OBS1) was designed to suppress amplification of DNA fragments derived from the otters. The 12S rRNA gene sequencing assay detected species belonging to fishes (95%) and amphibians (3.3%). Fishes detected by 12S rRNA gene sequencing included crucian carp (Carassius auratus), mullets (Mugil spp.), bluegill (Lepomis macrochirus), and northern snakehead (Channa argus), which were also detected by COI gene sequencing. Among invertebrates, mud flat crabs (Helicana spp.) and shrimps (Palaemon spp.) were abundant. The designed blocking oligonucleotide OBS1 effectively inhibited amplification of the otter’s DNA, with only up to 0.21% of vertebrate sequence reads assigned to the otter. This study demonstrated that HTS-based DNA metabarcoding methods were useful to provide in-depth information regarding diet profiles of the otters at our sampling site. By using HTS-based DNA metabarcoding approaches, future research will explore detailed taxonomies of their diets across locations and seasons.
Abstract. We developed a habitat suitability model for wild boar Sus scrofa in the Mt. Baekwoonsan region of Korea. We recorded wild boar field signs (dust baths, bedding sites, digging areas, feces and tracks) and habitat variables such as the nearest distance to watercourses (DWATER) and trails (DTRAIL), slope, aspect (ASPECT), forest type and forest age. Field signs and habitat characteristics were assessed within a 25 × 25 m quadrat along seven survey routes from August 1999 to July 2000. We conducted a CATMOD regression analysis based on 416 field signs at 50 points and classified them into 3 levels of habitat importance (high, medium and low) based on the relative importance of field signs. Habitat suitability indices (P) were calculated based on significant relationships between parameters such as DWATER, DTRAIL and ASPECT resulting in the following function: P = 1/(1 + exp -(3.82 × (DWATER) -1.21 × (DTRAIL) + 1.35 × (ASPECT))). Important habitats of wild boar were distributed near watercourses and far from trails along east and south-facing slopes.
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