No Tennis Ball Left Behind

I walk A LOT at home and for work. When I run Annie, I don't have her bring the tennis balls back to me that I throw. Early on I realized that if I did that, I would be standing in the same spot for an hour and not get any exercise. So I throw the ball and Annie chases it,picks it up and then lays down and waits for me to throw the second ball. When the grass at the park is tall I can't always see where the balls land. I have to give Annie the command to "find the other ball". This morning I must have had that lost ball look on my face because Annie started the search without being given the command. When she tracks down the ball she will put it next to the other one. Such a smart little puppy. :)