Canid competition for Arctic fox dens on the tundra

Natal dens can be a limiting resource for canids on the Arctic tundra, as frozen ground inhibits easy burrow excavation during the spring. Near Churchill, Canada, tundra dens created by Arctic foxes (Vulpes lagopus) have transformed into ecological hotspots (Sci Rep 2016; doi.org/10.1038/srep24020). However, while monitoring these dens for many years, we have observed that both red foxes (Vulpes vulpes) and gray wolves (Canis lupus) are also competing for these sites.

In spring 2021, one den became the site of a fierce canid competition. The den figuratively switched “paws” between both fox species, first being occupied by a pair of red foxes from March through mid-April, then by a pair of Arctic foxes in May. But the return of a red fox in early June led to antagonism between the two fox species, pictured here. Simultaneously, during the volatile period of occupation by one or the other fox species, wolves regularly visited this den, with at least seven visits documented from mid-May to mid-June. On the day that the wolf photograph was captured, all three canid species were observed on camera at the same den within 6 hours of each other. Eventually, the red fox was the last observed canid using the den, despite aggressive defenses from the Arctic fox pair.

Arctic fox abundance in this area has declined steadily for several decades, largely due to climate-induced changes in prey availability and abundance (Oecologia 2023; doi.org/10.1007/s00442-023-05418-6). As climate change progresses, what will be the long-term fate of these Arctic fox–created hotspots? Antagonistic interactions like those pictured here may foreshadow a slow turnover of Arctic fox dens toward occupation by larger, more dominant competitors typically associated with patches of boreal forest at the low-Arctic tundra border.