Per my understanding, the American red squirrel (Tamiasciurus hudsonicus) is a very different proposition from our European r.s. (Sciurus vulgaris). As PPs say, the American creature is a tough cookie -- in contrast with Britain's sweet, but retiring and timorous, red squirrel. I've long felt that we over here, need a red-squirrel equivalent of Richard Adams's General Woundwort, to rally his species and take the fight back to the grey invaders !