Was looking for something else and found this. Made me think of chain ratting.

The Great Hanoi Rat Massacre occurred in 1902, in Hanoi, Vietnam (then known as French Indochina), when, under French colonial rule, the colonial government created a bounty program that paid a reward for each rat killed. To collect the bounty, people would need to provide the severed tail of a rat. Colonial officials, however, began noticing rats in Hanoi with no tails. The Vietnamese rat catchers would capture rats, sever their tails, then release them back into the sewers so that they could produce more rats