A point I've been trying to get across for years is that Natural Selection works differently for white-tailed deer than for other herd animals. In most herd species, males will compete for dominance and then the dominant male collects a "harem" of females that only he breeds. This is Nature's way of ensuring that a male large enough and healthy enough (has expressed his genetic potential and his genetic characteristics have allowed him to win dominance battles) does the majority of the breeding.
White-tailed deer work differently. When herd dynamics are as Nature intended (balanced sex ratio and advanced buck age structure [50% of the male population 3 1/2 or older]), the majority of females will enter estrus over a short period of time (10-14 days). Since so many females are in heat at the same time, it is physically impossible for a few dominant males to breed all those does in that short of a time-span (a buck will spend 24-48 hours with an individual doe during the mating ritual). This ensures that the breeding is spread between a much larger number of males than in a "bull and harem" species. In fact, within a single doe social unit--where all the members are realted on the female side (they are all sisters, cousins, aunts, mothers, grand-mothers, etc.)--all of these does will enter estrus at about the same time, guaranteeing that each must be bred by a different buck and ensuring maximum genetic diversity within the offspring of that group (all the fawns from a single doe social unit for a given year will have different fathers--and studies confirm that is the case).
Why is this important? Because the white-tailed deer appears to have developed high genetic diversity within localized populations as a primary species survival mechanism. White-tailed deer thrive in an amazingly wide variety of environments; from the tropical rainforests of Central America, to the deserts of northern Mexico and the American Southwest, to the swamps of south Florida to the boreal forests of Canada. They are able to do this because of their extremely diverse genetics. No matter what conditions they are faced with, some animals in every population will by shear genetic chance be adapted to that new environment. Just the unique way Nature has produced for that particular species' survival.
This system would appear to produce no "Natural Selection" of the fittest male fathers, yet again, if you look at the DNA parentage studies, many bucks--even mature bucks--are doing no breeding at all. This means there is some selection at work, but it is not as intense of a selective process as that which occurs in "bull and harem" species. Now exactly what Nature is selecting for is unknown, but it is suspected to be large body size, resistance to disease, and aggressive personality.
