Abstract:

Aims: The Eurasian otter (Lutra lutra) is a key indicator and flagship species of freshwater ecosystems. Unfortunately, human disturbance and environmental changes have caused a severe decrease in Eurasian otter populations in China, even resulting in extinction in some areas. At present, the species is predominantly found in northeast and southwest China, with the northern part of the Greater Khingan Mountains being one of the most important habitats for Eurasian otter populations in the northeast. Studying the diet composition of Eurasian otter is a valuable tactic in understanding its interspecific relationship and the functioning of its ecosystem, which is essential when assessing their survival status and carrying out conservation efforts. The purpose of this study is to obtain the diet of Eurasian otter in the north of Greater Khingan Mountains using DNA metabarcoding technology.

Methods: In this study, 50 suspected Eurasian otter fecal samples were collected from the northern Greater Khingan Mountains. Based on DNA meta barcoding technology, 35 samples were confirmed to be Eurasian otter fecal samples. Then, using DNA metabarcoding technology, species in the identified feces were analyzed to gain insight into the diet composition of the otters.

Results: In this study, 22 species were identified as Eurasian otter fecal samples, including 15 fishes, 2 frogs, and 5 insect species. Cottus poecilopus had the highest relative frequency of occurrence (19.35%) and relative read abundance (27.32%) among all the vertebrate foods, followed by Rana amurensis (15.48% and 21.73%, respectively). At the family level, Cottidae had a significantly higher relative frequency of occurrence (32.26%) and relative read abundance (45.72%) than other fishes.

Conclusion: The results of this study reveal that fish, primarily from the family Cottidae, are the main prey of Eurasian otters in the northern part of the Greater Khingan Mountains in winter, followed by frogs. In addition, some aquatic insects such as Odonata, Trichoptera and Plecoptera are found in a small amount of otter feces, which might come from otter prey. This research provides valuable insight into the survival status of otter populations, and can be used to inform the development of relevant policies and conservation efforts.

Key words: Lutra lutra, diet analysis, DNA metabarcoding, non-invasive sampling, the Greater Khingan Mountains