A dominant buck produces higher levels of certain hormones than a lesser buck . Rack size plays only a small role in dominancy attitude,age,body size,and buck to doe ratios play larger roles. Say for instance you have a 10 doe per 1 buck ratio even a smaller buck may be dominant in his area due to not having much compitition for a doe. In a deer pen they can observe which are dominant . but just because a person has a deer farm doesnt mean they are experts on deer behavior .