My dad was a John Deere dealer...Back in the 60s a fellow came through selling a contraption that he claimed would scare deer out of the fields...It consisted of a timer, car battery, spark plug, natural gas tank, megaphone, etc...
You set this thing to make a huge boom every 15-30 minutes...
Within a few days, the deer were feeding around them...
One of the few times I remember my dad getting the short end of a bargain...