Our dog recently was kicked out of the dog park because she was being aggressive. At the dog park, she thinks that all the toys there belong to her and she takes the toys from other dogs and will growl and bark aggressively if she thinks another dog might take it from her. She doesn't show any aggression if a human tries to take toys from her, she only gets angry when other dogs do it. We really enjoy going to the dog park and our dog loves playing there. What can we do about her being so possessive over toys?

Hi lady. I met the same condition as you did actually before. My dog was very aggressive when I just bought him last year. Later I realized I could not treat him like a babyboy who's innocent and nothing know. A little dog is just like a kid we can not spoil him or her cos he or she would become naughty. just shout to him or even beat him a little bit ( dont get him hurt). gradually you will surprisedly find that your pup will listen to you and behave himself gentely.

I agree i had same with my dog, you just need to tell them off and gradually it will work.

Possession aggressive behavior is natural and normal for dogs, but unacceptable for humans. It is learned from their siblings at an early age. This reactive aggression by a dog is intentional and there is a reason for the behavior, at least from the dog’s perspective.
Food and Toy Aggression - Dog Training