Any given area can only support a certain number of deer(carrying capacity). When the population exeeds the carrying capacity, overbrowsing ocurrs. There is just not enough nutritous foods to support the herd. By thinning the doe numbers, there will be more nutritous food for less deer. The better nutrition a buck gets, the bigger rack he will grow. Also, less doe puts the breeding balance near the ideal ratio(2 to 1)......I hope this helps.