Hi, Im Sassy and I have two labs Black American Marley (8) and English Chocolate Lab Ace (3). Ace broke his hip when he was three and had FHO surgery and he did amazing with therapy and at home care. He is a normal dog who loves to swim, run and chase a ball. Lately, he has become somewhat aggressive to Marley when getting in and our of car. He will nip at her (not in a mean way) it just sound like that. Our dogs run off lease at a nearby place we take them. Some of our other dog friends come to play and Ace is find. Today, we came across a male neighbor dog and Ace became very aggressive and went after him. Both dogs are still in tact. Could this be the reason? or is he just trying to protect me. Other than that,he is a big baby and very gentle. Any advice is welcome. I have been very calm about the situation. He knew he was wrong and as soon as we got home, he put himself in his kennel. The door is open and he can come out at any time. Thanks in advance.