A few years ago, officials in Brooklyn, New York came up with a seemingly brilliant idea to deal with the rat-infestation problem in their borough: release opossums into the neighborhood to eat the rats. Once the rat population disappeared, officials surmised, the opossums would have nothing to eat and would disappear as well.
Like most ham-handed government efforts at social engineering, this one backfired: the opossums showed no interest in the rats, taking instead to rummaging through trash for food. Meanwhile, they procreated like mad. Result: Brooklyn is now overrun with rats and opossums.
Something similar happened on all the islands of Hawaii [about 100 years ago] when some genius’ brought in mongoose to eat the rats in the pineapple and sugar cane fields. Rats are nocturnal, mongoose aren’t. Most if not all the islands are now overrun with mongoose, which can be vicious, and of course, the rats are still there as well. Captain Cook brought the rats [unintentionally]; maybe that’s why the natives killed him.