Most animals shed tears to help keep their eyes lubricated — though the wily crocodile may never admit as much. But the consensus among experts is that humans are the only species that cries for emotional reasons.
Part of this may be to releases stress hormones, which make us feel better when we're upset or can calm us down when we're excited. Research also suggests that tears, whether happy or sad, play an important part in conveying our emotions to others and in evoking emotion from others. That connection leaves us feeling protected and supported, and helps to form closer, stronger relationships — a key survival mechanism. (Maybe the crocodile isn't the only sly creature after all).