I have two dogs, a 2 year old Cavalier King Charles Spaniel called Rambo and a terrier mix called Lana, who we think is about 18 months old.
We've had the cavi since he was a puppy, and we added the terrier to our pack about six months ago.
The two dogs get along great most of the time, but in the past couple of months I've noticed a lot more fighting over resources - namely dog toys and resting areas. These fights seem to be mostly driven by Lana. She was a stray dog that we adopted from a rescue, so it makes sense to me that hoarding items of value and protecting her favoured sleeping areas are probably ingrained in her.
Her favourite rest spot is one of our couches we don't use, and I've noticed her guarding it if Rambo is walking around. She'll also bite his ears or leg if he jumps onto the couch and a fight will start. It's the same if he tries to get onto an outdoor bed she favours. With the toys, she'll chase him if he has one, and once she gets it will defend it by lying on it. Sometimes I'll see a few toys on her bed which she's obviously hoarded.
Rambo likes to go after toys she has sometimes - like most dogs, even when you buy them the same toy, the one the other dog has is always more appealing - but I haven't noticed him protecting toys or even his sleeping spots, so I think it's mainly Lana that's starting this.
One other thing I've noticed, which I'm not sure is related, is Rambo loves playing fetch, but Lana doesn't. However, when you throw the ball for Rambo, Lana will chase him and try to knock him over. She has no interest in actually getting the toy, just seems intent on stopping him from getting to it.
Despite all this, the dogs are pretty good friends and get along together most of the time. And the fights have up til now been not too aggressive - mainly lots of mouthing and wrestling. I'm just worried that letting this behaviour go on too long, it will escalate - and worse, affect other dogs if we have to leave them with friends or in a kennel etc.
Any advice on how to curb this behaviour would be appreciated!