Estimating habitat-constrained home range size in semi-aquatic mammals: a case study on the critically endangered European mink (Mustela lutreola).

Accurate home range knowledge is essential for conserving species that are highly dependent on certain types of habitats. The critically endangered European mink (Mustela lutreola) is a wetland specialist whose movements are constrained by riparian and wetland habitats. In dendritic landscapes, conventional home range estimators such as Minimum Convex Polygons tend to include unsuitable habitats in estimated home ranges. Using VHF telemetry data from 16 individual-years tracked in France between 1996-1999 and 2020-2022, we compared four methods: Kernel Density Estimator (KDE), an adaptative sphere-of-influence local convex hull (a-LoCoH), a newly developed Ecological Home Range method (EHR), and a Generalized Additive Model (GAM) approach integrating hydrographic covariates. Our objective is to determine which method best accounts for the European minks specialization in wetlands, considering the spatial distribution of locations. Evaluation with wetland-specific metrics showed KDE consistently overestimated range extent and included unsuitable habitats, and a-LoCoH yielded mixed results, but these indicated that the method was not effective in excluding unused habitats. It was EHR and GAM methods that aligned more closely with ecological constraints. We therefore recommend GAM because it matches our objective and has the capacity to integrate additional environmental variables. Using the GAM, male home ranges averaged 3,074 ha--26 times larger than female ranges (116 ha)-- and were significantly larger in river than marsh landscapes. These are the largest ranges reported for the species. Large spatial requirements heighten vulnerability to road fatality and predation, both significant threats for remaining French populations. Our findings highlight the need for conservation strategies that integrate precise, habitat-based range estimates. The GAM method offers a robust, adaptable framework for managing European mink and other semi-aquatic species in complex landscapes.