East coast guy. No Muleys here, but I have seen a ton of predator hunting videos where Muley Doe will charge an ecaller playing fawn distress. Here on the east coast, whitetail does commonly approach my ecaller when running rabbit distress. I don't play much fawn distress, but given the doe's reaction to the rabbit sounds, I would guess fawn would trigger a response. I don't think I would expect the same from bucks, but you never know, I guess?