We always use the term "Mother Bear" when a human mother is being particularly protective over one of her children. It is true that you do not want to mess with a mother bear, but it is not only the predators that can prove formidable when it comes to protecting their young. A mother bison will always stand her ground in defense of her calf. I have seen up to four wolves at a time be defeated by a cow bison's determination and maternal drive. As long as the calf stays close, she will keep it safe.