Indeed Dosu weakness is rain and mold plus poison snake
Except for the first two, I don't think humans can handle snakes and poison either. But about wild yukkuri, yeah, those you mention are dangerous, but the things that wild yukkuri are easily prone to be as this pic stated: wild animal and winter. Not so much pool depicted that wild yukkuri is being poisoned or dissolved by rain, and they're smart enough to get away with those two (man, can't believe I write "smart" and "yukkuri" on the same sentence). Compared to that, wild animals, things like birds, snakes, boars, etc are much more common than poison. And winter is so harsh that they considered that surviving till spring is a commendable feat.
But you didn't say anything about the flood on your original comment...
Okay about the flood, again, even us, humans, as well as other land animals fear flood, it's not exclusive to yukkuri, like mold or winter.
Yeah, they have lots of fear that exclusive to them, but unfortunately, flood is not one of them, as almost all of the animal on this planet fear that thing, except for aquaric animal, and aquatic yukkuri is in this category.