I've written about this quite a few times as it is such an interesting area. Age, gender, size and a lot of things we might think are important don't actually seem that important to dogs. Their choice of leader tends to be the dog that commands respect in a benign way. After all the point is to NOT have fights within the pack, if you think about it! So often, the dog we think is the the top dog actually isn't -- it is simply the one the alpha dog lets get away with things.
Often it takes a professional behaviouralist to determine what the pecking order is, because it can be very subtle (and the order does change, too, especially when a leader ages to the point of losing command).
Also you do tend to need to be around a group of dogs a lot to start to sense which fits where but it can still be easy to get this wrong. In my house with three dogs, people always guess wrong about the alpha -- they think it is Jaspar, who was my first dog, is very closely bonded to me, and very playful. He almost always wins the tug of war games with his half brother Leo, and almost always gets the fetch toy first to bring back. Then people might think number two is Lily, as though she is very small, she is very opinionated with other dogs, and often snaps at other females when she's on the lead.
The bottom of the heap, everyone assumes, is my gentle and quiet Leo, who is a small male and has a melting face and the sweetest disposition imaginable. Everyone always loves Leo.
Well, Leo is the alpha. He is the most benign of benign dictators, the most easy-going boss, always cheerful and almost always ready to let others have the toys, etc. But if things come to a scuffle over a chew -- he will win and Jaspar will back down. If he does decide tog rab the fetch toy, Jaspar will play tug of war with him for it, but if Leo starts to carry it back, Jaspar backs down. And Leo has turned and snapped at other dogs who were bothering Jaspar even though Leo was at a distance and not being harrassed himself. Interestingly when we are on a walk and meet other dogs the main dog they are interested in is always Leo, so I think dogs recognise and also quickly acknowledge the alpha in a new group. Leo is also quite fearless of other dogs, including those many times his size, and will eye them if they are being rude, and growl as well. Jaspar is extremely submissive with other dogs and typically rolls on his back.
Lily meanwhile is very deferential to Leo and licks his face several times a day (and cleans his eyes, which he loves), a typical gesture of submission. But she also will not challenge Jaspar and always backs down if he wants something.
So the leader tends to be the one that quietly leads -- but if a scuffle happens, he or she will be the one that ends up with the desired toy or chew or whatever.
Your females may well be fighting with each other to establish order. The more dogs you have, the more pack behaviour you get, the more complex their relationships grow, and the more difficult they are to manage. Often females seem to be the ones who fight. If one is younger and just getting into adulthood, she may well try her chances at challenging an older dog or keep testing the others too.
