Habitats and population of European otter (Lutra lutra L.) in Abant Lake

This study, carried out in Lake Abant Nature Park basin, aims at the preservation of the Eurasian otter (Lutra lutra), a semiaquatic mammal of the Mustelidae family. The otter is one of the species native to Turkey that lives on land at aquatic areas and has international protection status; it is crucial to recognize the importance of this species as a factor in biodiversity and to contribute to its survival. Accordingly, the status of the otter, its population level, its habits and the threats to the species were investigated in the Lake Abant area; the relationship between the habitat properties that affect the use of area and the survival of the species were examined. The otter, which is the only aquatic member of the Mustelidae family, is difficult to observe as a result of its nocturnal habit and its timidity. Therefore, the study area was divided into forty 500 x 500 meter plots, and different ecosystems in each plots were evaluated. Data were collected using indirect observational methods (photo-trap images, audio recordings, foot–tail tracks, nest entrance, stool-food residues). Images, stool-food residue, nest entrance, and footprints of the species were usually obtained from the aquatic area. In photo-trap studies using 20 photo-traps that yielded 337 images, 403 otters were counted in 148 days at 171 points. Up to 4 members could be displayed in a single photograph. A strong relationship was detected between the number of observation days and the number of detected individuals (R2=0.89). According to months, the otter encounter rate was evaluated (F3:99=1.37, P=0.28), and it was determined that the species was photographed mostly in January and that the encounter rates significantly decreased in February, March, and April. No significant differences were determined between the displaying frequency in weekdays (P=0.3769). The encounter rate was the highest on Fridays, whereas it decreased on Saturdays and was the lowest on Sundays. The otter feeds on 41% fish and 40% invertebrates. In terms of aquatic fauna, the otter was generally detected in areas rich in peat. Evaluating the otter-carrying capacity of the area in light of the territorial behavior of the species and other findings, it was determined that 1 male, 3 females, and 7 cubs—a total of 11 otters—can live and reproduce in the study area.