It's the same thing with winter -- I'm in the consensus that yukkuri go into hibernation during winter, being that it'd be near-impossible for yukkuri to store up enough food to survive 2-4 months in a cave. Winter would be incredibly hard for them to hunt and gather in. They'd probably just live like bears -- crawl into their little caves and go to sleep, then while in that small and (basically) refrigerated cave, their paste would near-solidify into a slow churn. They could wake up once in a while to just have something to eat, but the species would have to evolve some method of surviving winter, or else they'd have been simply wiped out a long time ago.
IF you check the large number of works about winter they appear go into a dormant mode in winter although it is not really hibernation per se (See eisei's recently uploaded work http://oyp.yunyah.com/pools/1774)
Their winter stores may be explained if they do consume less than 5% of their body weight a day (like I said it's about 1.6% if their nutrition needs resemble humans) because that's about 150 grams of food a day if an adult yu weighs 3 kilos which is very easy to obtain.
In comparison a bluewhale consumes about 16,000 pounds of food a day supposedly and they get up to 400,000 pounds, consuming 4% of their body weight a day.
An interesting thing is if yukkuri were as voracious as shrews they'd be eating half or their own weight a day and we know that is not the case as most works show the result of a hunt hunt to probably well less than 1/8 the height of an adult yukkuri and that is considered a lot (unless the family is extra shitty).