Yungoose is a Pokémon introduced in Pokémon Sun and Moon that can be directly associated with mongooses, which were originally introduced to take care of the invasive rat population. This, of course, failed spectacularly. In the Pokémon world, however, it could be argued that the reason why the Alolan Raticate was so tough to beat was because its typing outmatched the Yungoose that were sent to e-raticate them!
Considering the fact that black rats are one of the main troublemakers in Hawaii -- aside from the Asian Rat -- I would say that this would act as the inspiration. The Alolan Raticate would then be a Dark type to reflect its new color, and it would make a whole lot of sense seeing as Dark type Pokémon have often been associated with higher defense and such. It would also be interesting to see Raticate become one of the few offensive Dark types, as it is one of the higher Attack and Speed stat Pokémon in the early game.