Feast to famine: Sympatric predators respond differently to seasonal prey scarcity on the low-Arctic tundra

Resource fluctuation is a major driver of animal movement, influencing
strategic choices such as residency vs nomadism, or social dynamics. The
Arctic tundra is characterized by strong seasonality: resources are
abundant during the short summers but scarce in winters. Therefore,
expansion of boreal-forest species onto the tundra raises questions on how
they cope with winter-resource scarcity. We examined a recent incursion by
red foxes (Vulpes vulpes) onto the coastal tundra of northern Manitoba, an
area historically occupied by Arctic foxes (Vulpes lagopus) that lacks
access to anthropogenic foods, and compared seasonal shifts in space use
of the two species. We used 4 years of telemetry data following 8 red
foxes and 11 Arctic foxes to test the hypothesis that the movement tactics
of both species are primarily driven by temporal variability of resources.
We also predicted that the harsh tundra conditions in winter would drive
red foxes to disperse more often and maintain larger home ranges
year-round than Arctic foxes, which are adapted to this environment.
Dispersal was the most frequent winter movement tactic in both fox
species, despite its association with high mortality (winter mortality was
9.4 times higher in dispersers than residents). Red foxes consistently
dispersed towards the boreal forest, whereas Arctic foxes primarily used
sea ice to disperse. Home range size of red and Arctic foxes did not
differ in summer, but resident red foxes substantially increased their
home range size in winter, whereas home range size of resident Arctic
foxes did not change seasonally. As climate changes, abiotic constraints
on some species may relax, but associated declines in prey communities may
lead to local extirpation of many predators, notably by favoring dispersal
during resource scarcity.