In my experience in the area I'm hunting. The smaller bulls throughout the last few years have been on the cows early in the rut. The bigger bulls will bugle but wont come into the cows yet. Once they start to get serious they push the smaller bulls out and become the herd bulls. I suppose every area is different as every year can be. I'm no expert but this is what I've noticed in my area the last few years. My area is doing the exact same thing right now. All smaller bulls with the cows and no big boys yet. I see them but they aren't with cows.