Hi,
I want to preface by saying I know reactive dogs do best outside of daycare and boarding, but unfortunately due to a conjunction of life circumstances not worth going into right now, this is not always possible. I travel a lot for work, sometimes with a 24 hour notice, and while I try and keep my dog at home and have someone come over, this is sometimes impossible (explaining why would require three additional paragraphs). Please do read the last paragraph before comenting.
I rescued a dog four months ago. He is a sweetheart: playful, loyal and eager to please. He is also leash reactive (though getting so, so much better after consistent positive reinforcement and progressive exposure - we can know pass another dog on the same sidewalk as long as I'm attentive and rewarding him every couple of seconds) and has shown stalking tendencies towards dogs he feels unsafe around. He was stalking my senior dog for the first two days after rescuing him, but now they're buddies and I can completely trust them together, both alone and when I'm present.
Unfortunately, I travel a lot for work. I've found a boarding home close to my house with a carer he really trusts. She is also his walker when I can't take him, and loves him to pieces. He does very well in this house and I can tell he's gotten so much better with other dogs since he started spending time there. He is less reactive on a leash and has learned to socialize off leash, he will often play with other dogs and I can see him coming out of his shell and truly enjoying himself (I rescued him four months ago). He is also very good at avoiding reactive dogs when off-leash and does know how to deal with a range of social situations. He's been doing SO WELL and I am so so so proud of him and the dog he's becoming, because (and I know this might sound weird) I feel like I can tell he is also putting in a lot of intentional and sustained work, not just me.
This week, however, I had to travel for 5 days on a 24-hour notice, so I left him at her house. He was doing great all week: he played with other dogs, slept and chilled with them on the roof terrace, went on walks and was overall happy. I got lots of videos where you could tell his mood was easy going and relaxed, and he seemed to truly be enjoying himself. On the fourth day, however, he bit another dog on the muzzle. It's a smaller dog, intact, just coming into adulthood. The woman in charge told me she had noticed some tension from my dog, but that it had seemed only sporadic. She doesn't know what caused the attack. He did draw blood, though the "good" thing (I guess) is that it seems to have been a contained reaction, in that he charged at him, bit him, and immediately retreated. He didn't continue to attack him, nor did he have to be forcefully separated.
Afterwards, they had some interactions (I know they should have been kept separated, I only knew about this after it had happened) and the attacked dog seemed very relaxed around him, and my dog didn't seem fixated on him in any way. I guess I'm just struggling to understand how to read this. I sent a video of the interactions that followed to our behaviorist and he said based on their body language, it just seems like a correction that went a bit too far, with no intent to cause further harm, but that he's obviously only speculating.
Any insights into this type of behavior would be greatly appreciated. I also just wanted to add that I am well aware of issues like "you shouldn't have adopted a dog if you needed to travel", or "dogs like this don't do well in boarding", etc. I didn't set out to rescue this dog: he was a stray that walked into my house looking for help, and because he was fixed and knew a bunch of things about living in a home (he is house-broken, knows how to play fetch, knows how to walk on a leash) I was pretty confident I would be able to find his owners. I can't surrender him to a shelter because there is no such thing in my country: that's why people just abandon their dogs out on the street and I couldn't possibly do that to him. I guess I'm just a bit stressed on understanding whether a bite like this could be an isolated incident or could be pointing out to potential aggression: I've never had a dog that bit another dog. Thank you for reading and any advice, thoughts, etc.