. . they've all been eaten by something larger. We do have rats, but they're wimpy rattus rattus rather than rattus novegicus so they're too big for mouse traps and too small for rat traps (but they do have a fatal attraction to florescent turquoise warfarin tablets).

I don't know why we don't have ratus n. - perhaps it's just too dry for sewer rats here, though the biped subspecies seems to thrive in Hollywood.