A bounty on rat tails accidentally created a rat farming industry
Facing a plague scare in 1902, French colonial authorities in Hanoi paid a bounty for every rat tail turned in, expecting locals to hunt the city's sewers clean. Officials soon found tailless rats running loose all over the city: hunters were cutting off tails and releasing the rats to keep breeding more of them. The bounty was quietly cancelled, having likely grown the rat population it was meant to shrink.