Seasonal use of American beaver lodge areas by gray wolves in Isle Royale National Park

Biotic and abiotic factors influence species habitat selection across space and time. Predator habitat selection is often studied in relation to their primary prey, however, how predators shift their space use in response to secondary prey and the corresponding ecological consequences have received less attention. We used four years (2018, 2020, 2021, 2022) of wolf (Canis lupus) GPS data to examine how wolf habitat selection relates to active American beaver (Castor canadensis) lodge locations. We hypothesized that wolf selection of beaver lodges would reflect seasonal beaver behavior, intensifying through the ice-free season as beaver vulnerability increases as they spend more time away from their lodges and the vulnerability and availability of moose (Alces alces) decreases. Using a generalized linear mixed model and a mixed generalized additive model in a Bayesian framework, we analyzed how wolf habitat selection changed, especially near active beaver lodges. We used 834 unique active beaver lodges in our analysis, 395 [0.74 lodges /km²] in 2018, 386 [0.72 lodges /km²] in 2020, 344 [0.64 lodges /km²] in 2021, and 168 [0.31 lodges /km²] in 2022, a total decline of 57% since wolf restoration. We collected 18,932 wolf GPS locations (N₂₀₁₈ = 1200, N₂₀₂₀ = 7224, N₂₀₂₁ = 3690, N₂₀₂₁ = 6818) from 23 wolves (10 females and 13 males). Our results suggest that wolves shifted their habitat selection to increase encounters with beavers, supporting previous work demonstrating the importance of beavers to the wolf diet during snow-free periods. This shift supports wolf prey-switching behavior to beavers when their primary prey, moose, are more difficult and riskier to kill.