Falling out....

[JaspersCarrott]

My very calm 5yr old show cocker, and my friends 11yr old cocker are friends - walks together, time together in my house & my friends - my friends cocker is extremely submissive, and they've been friends for 2yrs.
Over the last 2 weeks my friends dog has spent two afternoon with me, and my dog has attacked him on both days. Nothing seems to have sparked it, completely out of the blue.
This is the very first time my dog has shown any aggression towards another dog.
My partner has 2 dogs, and when we are there I think my dog sees himself as being bottom of the pecking order - at home i wonder if my dog feels like hes 'above' my friends dog, and wants to show his domination? I'm at a loss with what's happened, just wondered if anyone else has a dog who's behaviour towards another dog they have had lots of contact with has suddenly changed?

Do your partners dogs also visit your home?

It's one thing being out and about with other dogs but when they're in your dogs home touching his bed, toys, water bowl it can get a bit much for them and they can start to resource guard their things.

When you say attack what exactly do you mean?
Was it a loud growly telling off that stopped?
Did you have to separate them
Was actual biting involved?
And do you know what it was over?

My bitch resource guards and so we take precautions and we've had no more occurrences but this is because we know her triggers and she's with the other dog day to day so we could work on it.
With a visiting dog/s it will be much harder to work on.

What do you mean attacked ? Are the dogs spayed/neutered? Is the visiting dog touching your dogs things . I don't think a dog will see its self at the bottom of "the pecking order" if other dogs are not in the house.

Could the older dog be poorly op? I am fortunate enough to have a lot of dogs and the ONLY time I’ve had your experience is when one was poorly, even if they’d shown no symptoms and we didn’t know.
I have had dogs that lived together happily for decades with not a single cross word and suddenly have a fight. Every single time, the older dog was discovered to have a major medical issue.

I dog sit for my siblings dog and there .can be friction with my dog some times i.have to manage, so no shared toys eating separately, and i occasionally have to have them in different areas of the house so they can have a sleep/rest.

We had a dog walking friend. When she came into the house with her dog, that mine had always got on well with, he was horrified. The other dog clearly belonged outside for running around with, not sat in our house, on our carpet and on our sofa. Outrageous.

Had your visitor been in before with her owner?

The older dog has spent afternoons, stayed overnight without issue. Today he was here and had his tea meal, they have always been fed separately, as neither are used to eating with other dogs, and that has always been without any issue.
Both times my dog lunged at my friends dog, snapping and growling. My friends dog was cowering and yelping. I got hold of my dogs collar and he did stop, but then did try to have another go about an hour later, but I managed to see that before it really started and they spent the rest of the afternoon either side of a babygate - used to keep my dog safe as I've been having work done at home, not because there are children around - my friends dog tore his cruxiate ligament last year, and is seen for regular check ups, and nothing else has been raised about his health

My dog's neutered, my friends dog is entire.
My dog doesn't bother with toys, there are very few in the house.
The "bottom of the pack" comment was in regard to how my dog might feel when we are at my partners. His female dog is definitely in charge, and mine has made no attempt to dominate her or my partners male dog...but my friends dog is so submissive and laid back I just wonder if my dog is trying to assert himself. They are both on extendable leads when we walk, and there has been a bit of friction, just once, started by my dog - I thought that was just a one off, so maybe not just linked to being in my house

I think you need to be honest - do they actually like each other or do they spend time together because it’s convenient for the humans?

Nothing like trying to twist someone's post into something its not ...

Eh? You've said yourself that there's been friction between them on walks and now in your home there's been two fights. How is that twisting anything

If my dog had friction with another on a walk, even once, the last thing I would do is bring that dog into his home and safe place.

For 18mths there has been no friction either inside the house or outside... there has been friction on 'a' walk.... we have walked since without a problem - i asked about others experiencing similar behaviour between 2 dogs, not wether or not it affected my socialising with my friend - that's a stretch even Stretch Armstrong would struggle with

I didn't say anything about it affecting socialising with your friend

I was trying to figure out whether the dogs actually got on or whether they simply tolerated each other, that's all.

Nowhere in my posts has it been mentioned about walks being convenient for me of my friend. The dogs have always got along - more so than with other dogs - because up until the last 10 days - they are both calm, steady, not in your face spaniels - which is why it is so out of character for my dog. We met as dog walkers and our dogs got along. Initially the 1st 6mths was as and when we bumped into each other, and now we walk around 3 times a week - the fact that we get on as people is just a nice bonus

Which is why I was asking!

If they only tolerated each other, I would have just said to keep them separate - but if they've always been good together and there have now been two fights in quick succession, I would say both dogs need to see a vet to check for any unexpected pain or health issues. I would particularly want to check the older dog.

So which part of the OP did you miss? The bit that said they got on well together? Or the bit that said they've spent time together at times over the last 2yrs without issue?

This was my first thought as well when I read that it's the older dog being attacked.

OP, your dog might sense signs of illness that aren't apparent yet to you or your friend.

Blimey, I wish I hadn’t bothered.

Yes, good idea to get both checked out.