When I was on Oahu many years ago I heard about the mongoose problem.
The story goes that originally there was a rat problem on Oahu introduced from rats stowed away onboard ships. So to get rid of the rat problem which was out of control someone came up with the bright idea of introducing mongooses to Oahu. Unfortunately, they failed to do their homework.
If I remember correctly, rats are primarily nocturnal and mongooses are daylight creatures. Hence the two species often fail to meet, so both have continued to flourish on Oahu.