Not too far away, a young zebra is gamboling about by itself, every so often kicking out its hind legs for no apparent reason. Years later, each animal will have matured, and the zebra may find itself desperately fleeing from the pouncing lion, and fiercely kicking back its legs in an attempt to ward off the attack. Research into animal play has most often focused on the link between juvenile playfulness and serious adult activity. Humans have long recognized this correlation in themselves. Even to the untrained eye, animal play behavior can be quite obvious.
Countless examples pop up in the scientific record.
One researcher's hand-raised badger would often break into bouts of somersaulting. Young mountain goats are often seen rearing up on their hind legs, in impressive displays aimed at no one. Play is not seen only in mammals. Young garden warblers were observed again and again picking up pebbles and marbles from the ground, flying up to a branch and dropping them into a glass, producing a sharp jingling sound. Some have speculated that reptiles may even occasionally show signs of fun and frolic.