Some people say that a sign of high intelligence is the ability to use tools. In fact, at one time it was thought that only humans were intelligent enough to use tools. Other animals have since been found to employ the use of tools. 

Tools are used to make survival easier. Wouldn’t a greater sign of intelligence be the use of toys? Toys are used for fun and play.  Although I suppose the argument could be made that play is practice for skills needed later in life.

Still play does not support immediate survival. So I think that only highly developed animals play. Food for thought.