It is known from a wide variety of aquatic habitats, including highland and lowland lakes, rivers, streams, marshes, swamp forests and coastal areas. It is very adaptable, using saltwater as well as freshwater habitats, and even sewerage systems in urban areas. In most parts of its range Otter distribution is correlated with the presence of riverbank vegetation or rock crevices. Otters in different regions may depend upon different features of the habitat, but the important component of Otter habitat, for breeding purposes and daily rest, is the presence of holes in the river bank, including rock crevices, cavities among tree roots, piles of rock, wood or debris (Weinberger et al. 2019). The Eurasian Otter avoids deep water. Their distribution in coastal areas is strongly correlated with the presence of freshwater. The location of breeding holts is not confined to river banks; there is evidence to indicate that sometimes the species breeds well away from water and the pups are moved to holts on the river banks once they are a few months old (Ruiz-Olmo et al. 2005, Kruuk 2006). The availability of feeding resources is a key factor for Otter resilience and habitat suitability (Kruuk 2006). Diet is composed of aquatic prey, mainly fish, followed by crustaceans, amphibians and, to a lesser extent, reptiles, birds and mammals.

The Eurasian Otter was originally widespread throughout Europe, but it declined dramatically in the 1960s and 1970s, disappearing from parts of central and northern Europe (it went probably extinct in Liechtenstein, Belgium, Luxemburg, the Netherlands, and Switzerland; Macdonald and Mason 1994). Following strict protection and the banning of harmful pollutants by the European Union (EU), the species is now recovering in many countries, including Switzerland and Belgium. Since the 1990s it has been reintroduced to the Netherlands, UK, Spain, and Sweden. The Eurasian Otter is not found on most of the Mediterranean islands, although it is present on the Greek islands of Corfu, Lefkada, Euboea and Samos (Galanaki et al. 2019). Otters have been found in brackish waters below sea level in the Netherlands, and up to 2,400 m in the Pyrenees. In Russia, the range extends eastwards to the Urals (Loy et al. 2022).

The Eurasian Otter has the widest distribution of all otter species. Its range covers parts of three continents: Europe, Asia and Africa. Outside Europe, they have been recorded up to 4,120 m in Tibet (Reuther and Hilton-Taylor 2004).

It is strictly protected under international legislation and conventions: CITES Appendix I (Reservation by Russian Federation), Bern Convention Appendix II, EU Habitats and Species Directive Annexes II and IV, and EC 338/97 Annex A. Additionally it is protected under national law in many range states. A European Breeding Programme (EEP) for self-sustaining captive populations was started in 1985. Monitoring programmes have been established in many range states in Europe. Road barriers and tunnels under roads are required to reduce the impact of road kills. More monitoring is required, especially in non-EU countries. Environmental DNA (eDNA) approaches provide a fast and accurate tool for large-scale monitoring (Jamwal et al. 2021, 2023). Camera trapping is a complementary tool to monitor the efficacy of conservation measures, like road underpasses and artificial dens.