The bull
We can not see the bull in the photo that this sign is referring to, we guess it just might be quick enough to escape detection. If that is the case then it would probably be the best thing to not jump over this fence and trespass on this person’s property.
Who knows how fast bulls can run, we have seen some images of them at bullfighting events and know they have tremendous speed. But when we are running for our lives, usually we hit speeds that we also never thought were possible. We guess the only way to find out who is faster is to jump over after all.