Elsa has taught Penny the joy of sharing.
Penny was attacked a few days ago. Rest assured, she is fine now. She was at the dog beach in San Diego when she saw a dog playing with a ball, a Dalmatian. She approached and was about to check out the ball when the dog attacked; grabbing her by the neck and shaking. My daughter stopped the assault and made sure that Penny was okay. Then the owner slowly meandered over and said asked what had happened. The owner of the Dalmatian made several mistakes; the biggest one was not being there to see what happened. If you say "what happened?" in this type of situation then you failed your dog. This is an all too common scenario, ball aggression and it is NOT okay. Guarding.
I remember the almost identical thing happening to Luke when he was just around eight months old. We were at the dog park when he saw a dog playing with a ball and thought he'd join the fun. As soon as he approached the ball she hit him and hit him hard, knocking him to the ground. An Australian Shepherd that had no intention of sharing her ball threw him to the ground, gave him a few chomps and left him there not knowing what happened. No it was not okay and the guy who owned the dog was not okay either. He was an idiot; he saw the whole thing and was obviously unfazed by the behavior. We had a quick run around for a bit of fun before heading out.
Toy or object guarding is NOT appropriate in a public area. It is not okay anywhere but if you are dealing with such an issue at home, leave it there. Do not bring a dog that doesn't share well to a place where dogs are going to want to share. That or leave the items of sharing at home. Many dogs are just fine if they don't have their own objects to guard. When you enter into a dog park, beach or open area your dog may be required to share. That means that other dogs may approach and want to interact with whatever your dog has. If your dog is not okay with this then you should not be putting your dog into this situation.
I would not bring out raw meaty bones when we have a play date at our house. Toys are typically fine, Elsa loves to share because it means that there is a pending game. If a dog guards a toy or attacks another dog for looking at or touching their toy, you have work to do. That dog should receive immediate feedback and depending on the severity of the objection to sharing; removed and worked with before returning. If it is just a slight objection then feedback and try again.
If you see your dog guarding, really guarding; not just playing keep away then you need to address this. True guarding starts with a frozen posture, then a hard stare. Some dogs who are true guarders and regularly frequent the dog parks opt to go right to attack mode. They have warned so many times that they skip this step. That or their warnings are missed due to being at the dog park/beach where fun happens.
Guarding is a very natural behavior for dogs; teaching them not to guard is our job. If you have an object guarding dog then stick to running and playing with other dogs. Teach them the meaning of leave it and drop; for those times when someone else brings an object to the park. Yes guarding is a natural canine behavior but it is NOT okay to allow it in a public setting.