Hi Melanie,
Sharing is a human concept and the corresponding value in the dog’s psychology is tolerance. Dogs do not reason and plan ahead like us but only react and go by their instincts in most cases, and the instinct usually says to hold on to whatever they have as a matter of survival. They live in the moment and hence do not hold any grudges or anticipate a reward at the end of the day.
You have a playful and confident dog who does not know the distinction between his toys and other dog’s toy. The good thing is he is not aggressive. Teach him to respect your rules and wait for his turn to play. He needs to accept your authority and your ownership over his toys and take them only when they are given to him. This is especially necessary when he starts assuming ownership over your things or other kid’s toys as he would not make a distinction between dog toys and kids toys.
Establish the rule that he does not have access to all his toys at all times, but you will give him the appropriate toy at the appropriate time for him to play with. When he is playing with other dogs, teach him to wait for his turn. For example if you are playing fetch with many dogs, he needs to wait till you ask him to go. In general teach him to be patient while waiting.
When he is running around with the ball or any other toy, do not chase him around to get it back. It is again a form of play in the dog’s world and he will not distinguish it playing with a human or another dog. When he does this, you need to firmly call him back and make him drop the object and not forcibly try to take it from him. Consult a professional if you require help with the basic obedience training.
All this when consistently enforced, will enable him to understand that when others take ‘his toys’, it does not matter. He will learn to ‘share’.
Do you worry about your dog’s aggression? Write to pet.faqs@gmail.com