Well I did some research and it appears the the tree squirrels I am seeing now in the lower elevations are the eastern grey squirrel. Apparently, even though the Western Grey Sq can be twice as big as their Eastern Cousin, the eastern grey squirrel has been aggressively taken over territory from the the western grey squirrel. Does any one else have any idea about this?
From Wiki:The eastern gray squirrel has been introduced to a variety of locations in western North America. In Canada, to the southwest corner of British Columbia and to the city of Calgary, Alberta. In the United States, to the states of Washington and Oregon and, in California, to the city of San Francisco and the peninsula area of San Mateo and Santa Clara counties, south of the city. It has become the most common squirrel in many urban and suburban habitats in western North America: from north of central California to southwest British Columbia. At the turn of the 19th to 20th century the eastern gray squirrel was introduced into South Africa, Ireland and England.The Western Gray Squirrel was listed as a threatened species in Washington state in 1993. Populations of the Western Gray Squirrel have not recovered from past reductions. They are threatened with habitat loss, road-kill mortality and disease. Habitat has been lost due to urbanization, catastrophic wild fires, and areas of forest degraded by fire suppression and overgrazing, allowing the invasion of Scotch Broom. Notoedric mange, a disease caused by mites, becomes epidemic in Western Gray Squirrel populations and is a major source of mortality. Other species of Eastern Gray Squirrels, fox squirrels, California ground squirrels and Wild Turkeys are expanding and compete with the Western Gray.Listed as extirpated in some California areas, the Western Gray Squirrel in southern California is generally found only in the mountains and surrounding foothill communities. Local rehabilitation experts recount the Eastern Fox Squirrels were released in urban regions Los Angeles throughout the 20th Century. Fox squirrels (Sciurus niger) were introduced to the Los Angeles area in about 1904. Civil war and Spanish American war veterans residing at the Sawtelle Veteran’s Home on Sepulveda and Wilshire Boulevards brought fox squirrels as pets to this site from their homes in the areas surrounding the Mississippi Valley (possibly Tennessee). Other introductions of fox squirrels to the Los Angeles area may have taken place during more recent times but detailed records are not available. These aggressive cousins drove the more reclusive Western Grays back into the mountains, where competition was not so strong. This non-native species introduction appears to be the largest threat in the southern California area.