An animal in a state of panic can't function at all. I also think intense fear is an easier state for animals to get into than it is for normal human beings -- a lot easier. Animals feel intense fear when they're threatened in any way, regardless of whether they're predators or prey.
Fear of the number 13: A morbid fear of the number 13. Also known as triskaidekaphobia. Written reference to the superstitious fear of the number thirteen dates to the late 1800s. Its origin is conjectural (a matter of guesswork). The term triskaidekaphobia first appeared in the early 1900s.