In animals without limbs, the tail is the part of the body that extends beyond the anus. The term tail includes the fleshy part and the outgrowths it may have, such as fins and feathers.
Animals use their tails in many ways.
The tails of most water animals serve to move them and to steer them. Squirrels use their tails to keep their balance when they are leaping and climbing. Woodpeckers and kangaroos prop themselves up with their tails. Spider monkeys and opossums grasp things with their tails. Jerry F. Downhower, Ph.D., Professor of Zoology, Ohio State University.