I have two bitches, an 19 month old collie (spayed) and a 4 and a half month old retriever, both of which i have owned from 8 weeks old. They both loved each other to start with, they played for hours with very little upset. But about 2 weeks ago they started fighting. Nothing really bad, mainly play fighting that gets out of hand. I understand that two bitches together can be difficult and i know that they have to sort out whos most dominant out of the two but i was just wondering if this was normal. My older dog has been very depressed during this time, not keen on cuddles and generally being naughty - refusing to come on walks, refusing to sit, all things she knows how to do. She gets quite jealous when food or her toys around, and usually staarts an argument by nipping her mouth and staring at her whilst mirroring her every move. She will stop when told too though. It is difficult to see who is dominant out if the two, to begin with the pup would get possession of the toy in a game or argument and the older dog would submit but now it doesn't seem to be the case and it descends into an argument. My question is this, when these fights occur, should we intervene, or just let them sort it out between themselves? How long should we expect this to go on for?
Also a couple of times now when playing, the pup has got a little over excited and tried to 'hump' the older dog. I believe this is a dominant position. What surprised me though was that when she does this she 'leaks' (it doesn't appear to be pee) infact without being vulgar she kinda squirts liquid. What is this and what does it mean?

id deal with it by firmly stopping them, your boss not them -you dont want it-dont accept it !!!!

It sounds to me as if their relationship is going through a change as the younger bitch becomes mature. If the arguments are getting to the stage where the younger dog is perhaps not giving the older dog the chance to submit, she may be feeling that she needs to make her point more strongly - perhaps the way you're handling them as individuals is too equal? Just because a dog is more interested on one resource, doesn't mean that they will be 'dominant' (A truly dominant dog - ie, one who will stand up to a human, other than through fear, is a rare beast). From what you have said, if these were my dogs, I'd start to elivate the younger dog in situations that seem important to her - making sure she is fed first, gets the toy she wants (have three of any particuar toy they both like). I'd suggest the other dog is reluctant to go on walks because the younger dog is 'eyeballing' which is a dogs way of saying 'don't you DARE!' Sitting puts her in a difficult situation if the other dog is lying for example, as she is then higher which can be perceived by the other dog as being too 'cocky' if body language signals are important. Also we do tend to forget to teach our dogs to do things under different circumstances - teaching a sit in the living room won't teach it outside in the garden, or in the park, so she may need re teaching with the other dog around...........

However, you have said that niether has been injured - this is a good sign, as if bitches fight and get serious blood is split :(