Hey, so I now know why puppies are so energetic. A puppies fur has the ability to make energy using power from the sun. It is then stored there and when a puppy feels tired, the fur leaks the energy into the puppy, making her energy renewed. However, if she has not been in the sun for a while, her fur will lose the energy gained from the sun until she goes out in the sun again and creates new energy. As the puppies grow older, they lose the ability to do this, which is why grown dogs are less playful. The process of the fur making and storing energy is called: Camelsynthesis.