I know it sounds and looks great when your dog can play with sticks, balls, or other toys with strange dogs. Who wouldn’t like that! However, the reality is that a small amount of dogs can do this safely. I know there are exceptions but a majority of dogs aren’t the sharing type. For me, this does not mean the dog has behavior issues. It is more of a primal instinct where dogs guard things of value. Is if the dog in question is resource guarding food from you (their owner) then we have a problem. Aside from that toys are a high value item. When high value items are in the mix our dogs can get get overly aroused and stimulated. When you and your dog are playing this may not seem like a big deal, “yeah my dog gets jacked when playing fetch.” However, when another dog is introduced the game things can get can get sour fast. You may have heard or seen that dogs can make pretty crappy choices when over excited. This over excitement can lead to a nasty brawl even if things have been “ok” for a bit of time. You see I don’t expect strange dogs to share resources freely. I think that is expecting too much of them. Further, even if your dog does great with sharing toys, you have no idea how other dogs are with toys. They may become possessive as soon as they are in control of the toy and when your dog tries to get it, the other dog snaps. As a professional trainer we here of these things happening quite often. Often times they are said to happen out of nowhere. Sometimes, the dogs were doing great then a ball or some other toy is introduced and bam! A fight happens. The unfortunate side effect of a dog fight in your presence puts the dog in line to lose trust in other dogs as well as you. Dogs can have just as much fun romping around chasing each other without the added excitement of a toy. As always make sure you can start and stop the fun if you see things getting out of hand. If you want to play fetch find a quiet spot for you and your dog as that was probably the intention in the first place.