He or she will hide their tail behind their hind legs out of fear.
This is absolutely true, and you may have already noticed it if you've ever tried to feed a dog that is wary of people. He or she will put their tail between their hind legs out of fear, which is an obvious sign that they are frightened and do not like your approach. Simply be patient in this case, or put the food down and leave the vicinity; they will eat it later. When fighting with other dogs, they frequently tuck their tails between their back legs.