I was gonna answer that most animals don't live as long and reproduce faster than humans (so populations survive despite increased cancer risk), but when I looked into it I found a deep rabbit hole. In the case of wolves, I'm sure plenty died early on, because the populations present appear to have some genetic immune adaptations that protect them from cancer. I know other species (like frogs) have dark skin because the melenin increased the survival rate of the darker frogs at the time of the accident. So that is to say probably a lot of wildlife died, and that natural selection lead to some critters that are pretty resistant to radiation.