It is true that the farther North one goes the deer are larger as a genetic by-product of the environment. That goes for body, but not necessarily for horn growth. Northern deer still need decent genetics and old age to have good horn. This is something that can be duplicated in Southern deer by feed/management. Northern deer seem to have mass genetic, and curiously enough the colder it is for longer time periods the shorter the ears. I have heard that is because they freeze back, but in any case shorter ears can make a bucks' rack look wider.