n.
In zoology, actions that have all the elements of purposeful behaviour but are performed for no apparent reason.
Play has been documented only among mammals and birds. It is most common among immature animals, but adult animals also play. Horses, cattle, and other ungulates run and kick up their heels even when not fleeing from predators or defending themselves. Dogs adopt an aggressive posture to entice others to join in mock combat. Otters are well known for their mud sliding. Male birds may spontaneously perform their territorial songs when there is no intruding rival.