Hello!

Question:
I have two males, one is 4.5 years old, another is 15 months.
They have lived together fine, up untill about few days ago.
More and more they get into minor fights, chasing each-other, growling matches and such.
i realise, the younger one is trying to establish his rank in tha "pack" as well as "test" my older shepherd.
should I let them sort it out themsleves, but with some supervision, or should I NOT let them play together anymore???
We have about 3/4 of an acre, where they usually just run around, playing.

I'd keep them apart from now on. You've got to realize that "sorting it out" won't happen only one time. It will happen over and over, and each time there's going to be the potential for major damage to your dogs (blindness, lameness, scarring, infection). That's not to mention your family and friends who can get caught in the crossfire.

Pack dynamics will always be fluid. They might work it out for six months, and then something happens -- you get sick and loose your voice for a couple days, you are gone and your wife drops something on the kitchen floor, you get in a fight with your wife, whatever, and *bang* they can be right back at it.

Not worth the chance.

I agree with Stephan.Take no chances.Separate them.Damages can occur quickly.Not only physically but mentally to the less dominant dog or pup.Its great to see dogs playing and having companionship but you really have to have a keen sense as to what is "really" going on.Obviously your new pup may be getting just a bit more attention..this happens often.So judge your time with them equally...on their level of understanding.Create two areas separate that they can run..along the fence together for short periods.In doing so..your young shepherd will be able to walk away and not feel threatened by the older male.He won't have to establish himself.If the young male was dominated by the the older male already and he is high drive/strong..he may not walk away from the fence..he may say "Okay Buddy..you think..you are bigger and stronger than me"..."Lets see"...through the fence.Much damage can occur there as well.Bottom line..supervise your pups..know them love them..Please do not expect for them to just work it out..in freedom that you want to see.