Otter (Lutra lutra) is a strictly protected species in the Republic of Croatia whose protection is regulated by the relevant international conventions and regulations of the European Union. Otter monitoring (Lutra lutra) on the rivers Zrmanja and Karišnica in Zadar County was carried out in spring 2021. and autumn 2022. Data on the distribution of the species in the researched area were obtained by collecting data on signs of otter presence. Non-invasive research methods have been used. The samples were photographed and recorded using GPS. A total of 17 signs of the presence of an otter were determined, of which 13 of feces and 2 of leftover food. An anal gelatinous secretion was found in one case, as well as the presence of an otter in the form of finding its den. In the localities there is a greater number of signs during the spring period, which indicates that otters then feed much more intensively by taking from the environment available food sources. Data from the literature on the distribution of the otter and changes in the size of its populations confirm that the otter is a sensitive species and that its survival is directly dependent on human activity.