Predators at the nursery: Grizzly-Caribou spatiotemporal overlap in a declining herd?

Arctic warming is driving shifts in species distributions and predator–prey interactions, with important consequences for migratory tundra caribou (Rangifer tarandus groenlandicus). The Bathurst herd has declined to <1% of its historical peak, with no signs of recovery despite severe harvest restrictions and wolf control. Inuit knowledge holders in Kugluktuk, Nunavut, Canada, have reported increasing grizzly bear (Ursus arctos) activity and associated concerns about caribou calf survival, while recognizing predators as one of several cumulative factors influencing herd dynamics. To estimate the calving period and evaluate predator-caribou overlap, we deployed 96 motion-triggered cameras across the Bathurst calving grounds from May to August 2021. We found that cameras reliably estimated peak calving day and period (2 June ±7.81 days), demonstrating their value as a non-invasive tool aligned with Indigenous preferences to minimize disturbance. Grizzly bear detections overlapped spatially and temporally with caribou, while wolf (Canis lupus) detections were less frequent and showed weaker associations with caribou presence. Predator detections dropped markedly after the calving period, suggesting temporary aggregation on the calving grounds. Future studies that quantify calf predation and its demographic consequences, alongside other factors influencing Bathurst caribou population dynamics, are needed to inform management.