winter
That time of the year when the temperature drops and snow falls. Also a time of great trial for yukkuris due to their intolerance to cold temperatures, the decreased amount naturally occuring food such as insects or grass and water sources freezing over
Wild yukkuris will need to have had collected a food stockpile during autumn to hibernate through winter. A single mistake can lead to the demise of an entire family or even an entire clan.
City strays have it worse. Their main food source, garbage, can't be stored like a wild yukkuri's nuts and berries. In addition their cardboard homes aren't as coldproof as a wild yu's cave. Because of this, city strays generally have adapted to be able to tolerate cold better, but in exchange they'll have to bear the cold and go dumpster diving every day throughout winter.
For both wild and stray yukkuris, the most common cause of death during winter is caused by having kids during autumn. Having children increases the food costs of the family which is a problem during winter when food supply is low. Furthermore koyukkuris struggle to tolerate the cold of the winter and thus usually demand care and attention from the parents 24/7, further causing stress and exhaustion. This often leads to the parents performing eat up easy to feed their children only for their children to soon also die due to the lack of parents to care for them.
Most yukkuris are actually aware that they shouldn't have children during autumn. However particularly naive families often believe that for the sake of easy little ones surely they'll find the strength to prevail through winter. They won't.
Stray yukkuris are also more likely to approach humans during winter. This is because stray yukkuris will see that humans can take it easy during winter unlike yukkuris. Therefore they'll approach humans asking them to share their easiness (in the form of food and warmth) either out of desparation or out of jealousy (believing that they deserve to take it easy too, just like humans). As with most form of begging, this is often futile.