Raccoon dogs in northern Japan, north-east China, Korea and much of the introduced European range gain substantial body mass in autumn, largely as fat, then retreat to dens or burrows and become torpid. Metabolic rate and activity fall sharply. The dormancy is not the deep hibernation of a ground squirrel but an interrupted winter sleep, and animals emerge to move about during mild spells.
The behaviour is absent in populations living where winters are mild, which is consistent with it being a facultative response to cold and food scarcity rather than an obligate annual cycle. Pairs commonly overwinter together, matching the species' long-term monogamy.
The European population traces to deliberate introductions to the western Soviet Union for fur farming from the 1920s onward, from which the animal spread west across the continent. That makes it both a conservation problem, as a predator of ground-nesting birds and amphibians and a host for rabies and parasites, and a striking case of an accidental range expansion. Despite the mask, it is a canid, not a relative of the raccoon.