Urban, PeterHrdý, Tomáš2025-03-252025-03-252025978-80-87189-47-4https://repo.umb.sk/handle/123456789/277In: Zoologické dny Brno 2025 : sborník abstraktů z konference. 1. vyd. Brno : Ústav biologie obratlovců AV, 2025. ISBN 978-80-87189-47-4. S. 229-229.Hron is the second longest river in Slovakia. It springs under Kráľová hoľa at an altitude of 934 m and flows into the Danube not far from the place where the Danube leaves the territory of Slovakia. Mapping the river otter in a square grid is, despite the reservations, a method used to determine the spread of this species over a relatively large area and its changes. The distribution of the otter in the Hron river basin was investigated during five field mappings (winter 1995/1996, summer and autumn 2010, winter 2011/2012, winter 2021/2022, winter 2022/2023) using a modified IUCN/OSG standard method. It was about the evidence of the presence of a species, or its residence signs on selected 600 m sections of streams in the network of 48 squares of the Databank of the Fauna of Slovakia (approx. 10 × 12 km) and their 150 quadrants (approx. 2.5 × 3 km). During the first mapping in the winter of 1995/1996, the lowest number of positive squares (35; t. j. 72,9 %) and quadrants (71; 47,3 %) was recorded. Signs of otter habitat were mainly absent in the lower reaches of the Hron, but they were found near its mouth into the Danube, or on some tributaries of the lower Hron (e.g. Paríž). During further mapping, there was an increase in both positive squares and quadrants in the entire river basin. The increase was most pronounced in the middle and lower part of the basin. The highest number of positive squares (46; 95,8 %) and quadrants (125; 83,3 %) was recorded in the winter of 2021/2022.eninfo:eu-repo/semantics/openAccessvydra riečnaEurasian otterLutra lutracicavcemammalsHronmapovanieArticle