When it became easy to feed the family and the government of the day decided that they better make sure the "hoi polloi" didn`t starve to death , I would say the dog men decided to test their dogs on different quarry as it didn`t matter if the dog was hors de combat for a while as it was not the difference between a meal on the table and an empty belly, it probably became more in vogue when the lamping scene started as it was far easier to find a fox abroad during the hours of darkness than during the day, so probably around the late 1970`s early 1980`s I would of thought