I think dogs are the only animals that wag their tail when happy. Dogs wag their tail to convey that they are happy and friendly. Wild species like wolves and foxes wag their tail when they are young but they do not wag their tail when they are old.
Other animals that wag their tails for other reasons include: monkeys, horses, donkeys, cows, elephants, cats and many other animals. Most of them wag their tails to get rid of flies.
Graciously true. Tails are used for many things, not the minimum of which is correspondence. A dog tucks it tail when panicked and wags when cheerful. A feline cuts it's tail forward and backward when angry. A fox make use of it's tail as a cover to keep warm and an elephant utilizes it's tail as a hand for it's child to clutch. Numerous creatures utilize their tail for adjust, similar to a squirrel or a feline, or as rudders and propellers in the water, similar to a beaver or otter.
Fish utilize their tails for impetus by waving them side to side, while warm blooded animals like porpoise move them here and there which additionally enables them to move themselves out of the water for air. Peacocks utilize their tail to court. Creatures with long tails with tufts of hair on the end, similar to giraffes or dairy animals, utilize their tail to swat flies. Flying creatures utilize their tails to fly. Monkey's and opossums have prehensile tails that demonstration like another hand.