It has been noted by a recently retired librarian that there were no squirrels when he moved here (a Willamette Valley town) some 30 years ago, and there are now gray and red squirrels coming into town. Certainly I too have not seen squirrels here for 9 out of the 10 years of living here, until this year. This is not an area that has been highly developed, not at all, just the fields of the valley have not been friendly and the increased trees because of human cultivation have improved habitat locally, no need for introduction. Of course, coyotes are coming into town too now which is also new.