The main reason I heard is lack of nutrition. It's hearsay, as I don't really know. Typically the timing of when the antlers are suppose to come off, is when they are done breeding. Maybe he's had a good year?

Antlers fall off anywhere from December to March. I've seen some guys walk up to their buck, of which have been substantially large racked, and pull the head up for a good camera pose and have an antler pop off! LOL! Have also seen hunters cringe when their buck takes off running after a shot because they know late season, a buck can knock his antler(s) off when he finally meets the ground.

The little guy also may have gotten away with his life after an encounter with a vehicle?

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