Habitat selection of Eurasian otters (Lutra lutra) in urban rivers: the effects of urbanization, water quality, and river structure

Abstract

This study was motivated by the increasing presence of Eurasian otters (Lutra lutra) in densely populated urban areas despite their well-known susceptibility to urbanization. We assessed the spraint marking intensity indicators along the Gwangju Stream in South Korea in 2020 and 2021. In this study, we aimed to determine otter habitat preferences in an urban river and examine the impact of urbanization, water quality, and river structure on otter habitat selection. We tested two hypotheses: (1) otters inhabiting urban rivers are more likely to favor suburban areas over highly urbanized areas, and (2) heterogeneous habitat conditions in urban rivers promote otter presence. We utilized generalized linear mixed models (GLMMs) and self-organizing maps (SOMs) with 21 variables (eight related to river structure, seven related to urbanization, and six related to water quality) to elucidate our hypotheses. Our results indicated that otter spraint marking intensity indicators were more prevalent in highly urbanized areas, with river structure serving as the primary factor influencing otter habitat selection in urban rivers. Our SOM results highlight the possibility of otters inhabiting highly urbanized areas in scenarios where artificial structures perform a protective function and extensive gravel pits serve as alternative habitats. This study suggests that coexistence between humans and otters is possible, and it may contribute to the development of sustainable urban planning strategies.