This is a recessive genetic trait that is usually linked to piebaldism. It is not due to inbreeding. Inbreeding is not an issue in deer just deer hunters.
Just shows that you can't believe all the information you hear. I had understood that it was a genetic trait that was the first sign leading to piebalds and was a result of overpopulation which lead to interbreeding. Guess you can't believe everything you read on the internet and hear on the TV news.
I killed this buck a few yrs ago. He was super skinny and I noticed when he came out he kept turning his head sideways to eat the peanut vines. After killing him it made sense why. He couldn't nibble str8 on because of his under bite.
On a side note, I have pics of him the previous year as a 7 pt. Looks almost identical to the season I killed him as an 8. Gained very little width or mass, just an extra point. Like I said, very skinny compared to others around him. Wondering if the underbite effects growth. I would think it somehow limits food consumption. He wa at least a 2 1/2, I believe more than likely a 3 1/2 year old.
Higher population of deer, high number of deer in a small area and many of these deer will be related. Add in recessive genes in this population and there is a higher probability of the traits showing up. That is not to say these traits could not show up in areas with low deer densities as long as the recessive genes are there.