It started in the summer, he had so much fun chasing stones in the sea or river we then started throwing a couple on walks. This coincided with his recall going out of the window but he'd stay by our side if he thought we had a stone for him to chase.
He doesn't catch them, he chases them then sniffs around for them. He'll occasionally find it and pick it up in his mouth then drop it.
I've tried to get him into balls or other toys but he's not interested at all. It's now his favourite thing to do and the only thing that holds his attention when he's off lead. He's 13 months old. I don't really know what to do about it.