My almost 8yr old black lab has started being aggressive towards other male dogs that we meet out on walks. He has already been castrated, a number of years ago. The odd thing is, sometimes he is completely fine, and other times, he just launches at them. He's the same whether he's on or off lead, but I've started putting him on the lead as soon as I see a dog I don't know. It tends to be dominant dogs that come over and approach him that he takes a dislike to - if they ignore us then he ignores them. And he seems to be ok with bitches. I work this dog and he can work with entire dogs on the field and not bat an eyelid, although he is defensive of his birds and guards them. He will sit stay next to these dogs and not react, and then one will look at him in the wrong way and he launches at them. The problem isn't so much when he's shooting as all those dogs are focused on working too and so they all just ignore each other and do their job. It's when I walk him locally on the park and other dogs come bounding over to him and then they're in his space and he gets really aggressive (and I'm often trying to hang onto my 7 month old pup at the same time). Incidentally it started before I got the pup, but has got worse since she came along.... Any thoughts on how I can nip this in the bud and get my nice-natured boy back?
You really need to engage with a canine behaviourist who can assess your dog and the triggers/behaviours and suggest a behaviour modification plan. Without seeing the sequence of events and body language it really isn't possible to suggest appropriate action.
