Nonverbal communication
Animals other than humans do not have our kind of language, but they make use of non-verbal communication. With many, scent plays a greater role in their communication. Also, social animals can get to understand the meaning of tone of voice, and even understand key words. Say "walkies!" to the family dog... With animals which are social and intelligent, humans can have a genuine relationship. In general, that means animals which are mammals or perhaps pet parrots. Communication of the non-verbal kind is strongly developed in mammals, and mammals are mostly social animals.