Why is my dog going after another dog?

Question

I walk my dog early in the morning when it's still dark. Being half awake and the darkness I can't see all that's going on, or has gone on.

My dog is a blue tick hound. He was a rescue dog, and he has been to doggie day camp and I have seen him with little dogs before and he will just let them be. The people at the doggie day camp all love him and say he is a very positive influence for all the dogs, big or little. He loves almost everyone except the newspaper guy and mailman, but I think it's the smell of the paper.

When people lurk at me he is also very protective. There is a woman who walks her little dog also in the morning. My dog goes wild over this little thing. By wild I mean you would think he wanted to kill this little dog. Other little dogs have yapped at him and come very close to him but he never loses control. When he was in foster care the woman had her own little dogs. Maybe he has the same resentments he had then toward that breed of dog. I have had him close to four years and he had several quirks then. The woman is not walking by our house. Do you have any idea why he would do that?

Answer 1

If by going wild you mean that your dog simply wants to get as close as possible to the little dog, without showing signs of aggression, then your dog is most likely sexually attracted by the little dog. To confirm this, you should ask the owner to tell you whether or not the little dog is a female in oestrus. If not, it may also be the case of your dog making some "hormonal"(in case of being neutered) mistakes when deciding to persuade the little dog.

If your seeing aggression, then it may be the case that your dog competes with the little dog in their game of marking their territories(possible over the urine of a female that is in oestrus). That is, the little dog is very keen(happens very often) on urinating over your dog's urine and it may be the case that your dog gets angry while sniffing his urine.

A less probable situation might be, in which, you're seeing, one of the symptoms of hypothyrodism(possible outset of the symptoms), which is unjustified aggression.

Answer 2

TL;DR

Your dog shows high levels of arousal when the other dog is present during your walks. This is really the only conclusion you can draw.

Regardless of the reason for the arousal, the simplest solution is to increase distance from the source of the arousal until the reactivity diminishes. You may have to experiment a bit to find the right distance, but in my own experience a half-block to a full city block is generally sufficient.

Analysis

There are a number of possible causes for the behavior you describe. These include:

1. Leash aggression.
2. Prey drive.
3. Barrier frustration.
4. Inhibited social cues caused by frontal approaches or social deficits in either dog.
5. Territorial aggression.

If your dog does fine at daycare, and only has problems on walks, the differences are primarily the location, the leash, and you. It is also possible that there is something about this one particular dog that triggers a reaction from your dog; from the limited information that can't be discounted.

Attributing "resentments" to a dog is anthropomorphic, and clinically unsound. The only accurate thing one can really say is that your dog shows high levels of arousal when the other dog is present during your walks. Whether or not you need to do anything about this, other than ensure a safe distance for all parties, has a lot more to do with your level of distress with the situation than it does with your dog's state of mind.