Aquatic and Terrestrial Environmental Correlates of Eurasian Water Shrew (Neomys fodiens) Habitat Use in the Lesser Khingan Mountains

Understanding habitat selection is essential for predicting species distributions and developing effective conservation strategies, particularly for semi-aquatic mammals. However, habitat requirements of the Eurasian water shrew (Neomys fodiens, EWS) remain poorly understood in northeastern China. We investigated habitat use by comparing 44 used and 44 control plots in the Lesser Khingan Mountains during winter and spring. Aquatic and terrestrial environmental characteristics were evaluated separately using generalized linear models and multimodel inference, and supported predictors were subsequently combined in an integrated model. Habitat use decreased significantly with increasing distance from water (β = −0.333, p = 0.008), was higher in still-water than in fast-flowing habitats (β = 1.728, p = 0.04), and was substantially lower at upper-slope than at lower-slope sites (β = −2.712, p = 0.02). The integrated model received stronger support (AICc = 101.62) than the aquatic (AICc = 106.21) and terrestrial (AICc = 110.50) models and showed the highest discriminatory performance (AUC = 0.853). This advantage was retained under repeated stratified 10-fold cross-validation, with a mean AUC of 0.786 ± 0.013. These findings indicate that EWS habitat use is better characterized by considering aquatic and terrestrial environmental characteristics jointly rather than separately and highlight the importance of the aquatic–terrestrial interface for habitat assessment and conservation of this semi-aquatic species in northeastern China.