I think it grew that way, I say that because I've seen a buck with a short lower jaw before. A guy in our hunting party killed a buck in the Maine North woods once that had a lower jaw exactly like that, it was perfectly healthy,
I Started to shoot it, But it was doing really good eating and pretty Healthy!! So I Shot it with My Camera! I Take my camera everywhere with me! Love taking pictures of Deer and Wildlife while I'm Hunting or Fishing!! Thanks for the Info!
It's most likely a birth defect called brachygnathia, occasionally deer are born with a shortened lower mandible. I usually see pictures of one about once a year somewhere in the state.