I am a wildlife biology major and from my knowledge so far many hunters believe that the bigger the tree the bigger the deer. Come to find out that really isnt true. Small bucks will hit big or small trees just the same as more mature whitetail. Though the majority of bigger rubs are made by mature bucks as a sign of dominance. Another way that might help distinguish is how high up on the tree the rub is. If there are tine marks up quite a ways on the tree then he probably has a fairly tall rack.