Agressive behavior or play. Dog becomes highly agitated when he sees other dogs, cats, male humans. He will slip his harness to get to them. I am a senior and find him hard to control while we are walking. He iIS obedient but since he was rescued I do not know his history. I ws told his owner was placed in a hospice and he was abandoned. He has a small notcch missing from his right ear and small scars around the top of the right eye. He is friendly and loving and also has a voracious appetite. Is hungry all the time and has gone from underweight when I got him 5 mos ago. He weights about 11-12 lbs. He is robust and plays lustily with his stuffed toys that squeak. He is well house broken. Why does he "mark" most every bush, etc we pass. Is he asserting his presence in nearby territory?