If we can eradicate them, at least the ones that carry disease, then we should. Unfortunately we can’t really do that. But the idea that every species must be preserved is completely without any basis in the Torah or in logic. We have Boruch Hashem wiped out the smallpox virus. It is extinct and that is a wonderful thing. If we can make more dangerous species extinct, that would be wonderful too. Hashem’s creation is imperfect. He left the world unfinished so that we would have room to improve it. And one way we do so is by removing dangers from the world.