Men often think about getting something to wear that makes them stand out, some chain or dogtag for their neck. They often go by look, not thinking twice about buying it from some sketchy store, ignoring the pendant attached to it. They never realize how much is at stake as they add it to their wardrobe.
They don't notice anything at first when they wear it. Their minds are never super busy in the first place, not realizing how much emptier it it. Time begins passing much faster, their lower self-awareness unable to tell. They've never cared too much about their appearance, ignoring the immense amount of hair slowly spreading across their body. Their simpler mind forgets their shaving routine, allowing their stubble to grow into a full beard.
Their minds and bodies become more doglike, barely able to do anything but follow orders. Their eyes begin trailing after men, attached to their jeans hoping for a bone. It's only then they realize something could be wrong, but by now their minds are too far gone to do anything about it. Their beard has already covered their dog tags at this point, and being unable to see it, they won't even consider it a possibility.