Since animals have evolved next to human for thousands of years, they have learned to show their feeling towards us; Dogs will wag their tag, lick you, step on your feet, press their body against your legs, lay on you, etc, all in effort to show affection and be as close as physically possible to you. Cats make eye contact and slowly blink at you to say 'i am comfortable, I am pleased', they headbutt you as their form of a hug, they groom you as they would a kitten to care for you, they rub their scent on you to say 'this is my human, all mine' and it reassures them of your bond. Cows will also groom you, and enjoy being pet as it is relexing and they truly trust you. Also elephants get excited and happy looking at humans because we are to them as dogs are to us- they think we're cute, and want to play and pet us.