A: Genetics, injury, and food supply all play a part. I've seen deer with massive, well-formed, but nontypical antlers that were probably passed on to them. Others, with one typical and one nontypical antler, have suffered an injury. I once shot a deer with antlers so weak that they snapped off when he hit the ground, and that was in a year when the mast crop had failed. The deer was most likely a victim of poor nutrition.