Density can have an effect on the size of deer if they are overpopulated, limiting the food resources, however from what I have read and heard, deer are larger up north due mainly to the fact that larger animals have a higher survival rate in cold climates because thier body mass allows them to not only be warmer, but gives them the ability to go longer periods of time during the lean periods of the winter with less food than a smaller deer. In Va. deer tend to be larger in the areas where a lot of soya bean and corn are raised than in the mountains.

The Tazman aka Martin Price
Proud father of a Devil Dog