I have a 13 month old boxer that we care for a lot, but she has started showing signs of aggression about 5 weeks ago, this started after my husband left to go out of town to work. On our walks she will see another dog and go into a frenzy out of control and even bites me or anyone stand beside her, she has never drawn blood, but worries me that if I can't get it under control it may happen.
Some boxers do just seem to have a frenzy aggression towards other dogs, not saying that other breeds don't have the same problems but we do tend to see it a lot in Boxers. Does she do it on-lead and off-lead?? One option is that it may be a Lead-associated aggression:
Dogs are compulsively social animals. When most dogs spot another dog on the street, they are highly motivated to approach and investigate. If they are on lead at the time then they are restricted from doing this which leads to frustration. This frustration translates into increased excitement and agitation, which can be alarming to the owner, who may then deliberately hold the dog back, tense up before encounters or even punish the dog. This starts an association between the sight of dogs and frustration as well as owner tension and possibly punishment. A vicious cycle is then born and may lead to redirected aggression towards you, the owner. This and the fact that they are guarding you is why more aggressive behaviour arises on-lead than off.
Part of the solution is recognizing how unnatural it is for dogs to meet other dogs without the freedom to approach, sniff etc. You should allow her to approach and investigate friendly dogs but only let them do so after they have performed a "please may I" command such as "sit".
Due to the problem being a recent change I think this should be enough, however if it was a chronic case of lead-associated aggression, a combination of disocciation(making the lead experience a positive experience), obedience training and controlled socialisation may be needed.
