We only had red squirrels (dunno 'bout any sub-species) but few of them survived the onslaught of the "imported" American grey squirrel (never expected to learn about wildlife on a Jeep forum but all this talk of subs with strange sounding (to me) names comes as a revelation.
As far as the ol' lady was concerned they were all tree rats, I think, and she referred to pigeons as flying rats - or some such.
"called them that back in PA" reminded me that something I've noticed from forums but more particularly U-tube channels is how some terms/expressions I always considered peculiarly English enjoy currency in the US (or, at least, some parts) - & now I'm beginning to wonder if my care translating my posts, particularly the names of tools & car parts, into "American" is misconceived, because it seems that in same places the English term, or pronunciation, is in use.