I worked in that area in 1970, but did not see the rats - I was never in the crater though. I am not surprised it did not worry about humans - the locals are frightened of the crater (possibly with good reason - to call it "extinct" is probably premature at best - think Mt Lamington!) and never go there. No doubt if they did visit the crater and knew of the rats they would be extinct - I can't see them regarding the rats as anything other than edible; historically they had no problem with regarding their neighbours as food.
I was aware at the time that the mountain represented an "island" with many unique species - at one stage there was an army unit there whose CO had deliberately selected the area for an exercise so that he could indulge his hobby of describing new species of birds.
John

