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Old 12-25-2020, 11:29 AM   #59
Longue Carabine
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Join Date: Jun 2015
Hunt In: Medina County

Originally Posted by Sika View Post
Without reading all of that, I can see how nutrition plays in a role in survival of the fittest where the healthiest, largest deer survive to produce more large, healthy deer. Over several generations, you would have a population of bigger deer. Small, unhealthy deer are more likely to succumb to malnutrition or fall victim to predators.
However, genetic factors largely account for the body size. You could take a bunch of Llano county fawns and drop them in a high fence in Webb county. At full maturity they would still not rival native South Texas bucks. Even when maximum body weight and antler size are achieved, genetics are a limiting factor, not just antlers but skeletally as well.
The key to understanding this is something called epigenetics. Epigenetics can manifest in a single lifetime or over several generations, and to varying degrees in between. I will summarize what happened in South Dakota because it answers EXACTLY the question posed by this thread, and your hypothetical example. Whitetail deer in the black hills were small in comparison to the whitetail deer in the southeast of the state. So much so that many suspected they were different subspecies. So they designed an experiment to find out. They created two enclosures in the same place, one for a population of black hills deer and one for a population of southeast whitetails from SD. They lived in identical conditions, were fed identical feed, had no predation, etc. Within one generation, the size difference continued, but during the second generation the black hills deer began to close the gap, and by the third generation they were about the same size. There are two hypotheses about why this happened. Both could be true or just one of them may be true. The first is maternal nutrition. This theory says that the future potential off the offspring in adulthood is determined by how healthy the mother has been her entire life and the positive effects that imparts on the fetus. Each generation of lifelong excellent health contributes to added benefit (up to a plateau). The other theory is epigenetics, which are changes that your genes can exert on you IN RESPONSE to external stimuli. This can happen in many ways and diffent ways depending on species, but in this case it's all about size and cost vs benefit. If a deer lives in the black hills where nutrition is less abundant than the SE of the state, then it is disadvantageous to be big because big bodies are more expensive in terms of food. So being unable to keep a larger body well fed would lead to a less successful, fatigued, disease prone individual. So their genes regulate body size based on food available. And because it is a life or death commitment, the genes won't commit to dramatic size increases skeletally unless that increased nutrition has been consistently present over several generations.

Last edited by Longue Carabine; 12-25-2020 at 11:36 AM.
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