Wolves on ice: habitat use and selection of water bodies by wolves during winter

Terrestrial mammals are in many ways connected to water bodies, although studies on habitat selection within anthropogenic landscapes often overlook the importance of water. The recolonization of grey wolves, Canis lupus , across parts of Europe, together with developments in GPS technology, has offered opportunities to study detailed spatial movements of this large carnivore in human-influenced landscapes. Here, we investigated wolf use, habitat selection and step length in relation to water bodies in the boreal forest during winter. We hypothesized that wolves select for larger water bodies during ice periods and use them as travel corridors for efficient movement, similar to forest roads. We used step selection analyses with data from 71 GPS-collared adult wolves in 44 wolf territories in Scandinavia to investigate habitat selection in relation to water bodies, time of day and season. The study included >50 000 GPS positions taken at 4 h intervals between 2001 and 2023. Wolves selected for lakes and rivers during ice periods, especially at night, with step length increasing when travelling on ice. Deep snow generally impeded wolf step length, but not more on frozen water than in other habitats. These results indicate that wolves utilize frozen water bodies as travel corridors for easier mobility during winter, possibly to reduce human-encounter risk. Our findings emphasize the adaptability of wolves and, more generally, contribute to our understanding of mammalian movement patterns and space use in the boreal zone. • We used step selection analysis to investigate the use of water bodies by wolves. • Wolves selected lakes and rivers during ice periods, especially at night. • Wolves moved more efficiently on ice, suggesting its function as travel corridor. • Deep snow affected wolf selection of forest roads, but only during daytime.