Diesel is 8 months old and he attends a doggie daycare with lots of other smaller dogs (eg. frenchies, chihuahuas, yorkies, bichons etc.) I thought it would be good to socialize him early, so I've been taking him for full days once or twice a week since he was about 6 months. I went away on vacation for a week and left him with a friend of mine that has a boston terrier. The first few days back at daycare, the workers have started noticing some aggressive behaviors, especially when other dogs get yappy and excited around him, he'll respond by standing very still and then growling and finally using his body to charge at them. I'm wondering if this might indicate he's overstimulated or territorial? When this happens, it is usually targeted to one specific dog that pisses him off. They separate him from the rest but then he goes crazy and barks and gets distressed evident by his pacing and trying to get out. The daycare workers are very good and they correct the behavior but I am scared that he will escalate and hurt another dog. They are willing to keep working with him but I wonder if it's better to just pull him out of the environment if it's too much for him. Any ideas???
Other info: when I take him to the dog park, he usually doesn't play with other dogs, he might have a quick sniff but he just likes to play fetch. When he has a stick or a ball, he growls at other dogs if they try to take it or even if they come too close to it. I realize he's become possessive of toys/ sticks and we have been working on "leave it" and "release" but there is still more work to do (he's about 50/50 right now). He also growls at other dogs if they sniff him too long or follow him around.