Mount Graham Red Squirrel
(Tamiasciurus hudsonicus grahamensis)


The Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis) is one of twenty-five subspecies of red squirrels found throughout North America.

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The Mt. Graham subspecies is found only on the Pinaleņo (Graham) Mountains of southeastern Arizona.  They were believed to be extinct in the 1950's, but were "rediscovered" in the 1970's.  The squirrel was added to the Federal endangered species list in June 1987 by the U.S. Fish and Wildlife Service.

The Mt. Graham subspecies has been isolated from other subspecies of red squirrels since the end of the Pleistocene glacial periods approximately 10,000 years before present.  Recent studies have shown that the Mt. Graham red squirrel differs genetically from the other red

squirrel subspecies found in the nearby White Mountains and elsewhere in North America (Sullivan and Yates. 1994. Storm over a Mountain Island. University of Arizona Press, Tucson, AZ).

Initially, some biologists believed that the Mt. Graham red squirrel could only survive in spruce-fir habitat on the mountain range, resulting in an 800 hectare (1961 acre) area of the highest elevations ( above 3048 m or 10,000 ft.) of the Pinaleņo Mountains being designated as critical habitat.  In 1988, the U.S. Fish and Wildlife service designated most of this area as a red squirrel refugium.  Access to the refugium is restricted by a permit system administered by the USDA-Forest Service.  This action has also served to protect three high elevation cienegas (wetlands).  Since 1989, however, significant numbers of red squirrels have been found at lower elevations on the mountains, calling into question the validity of designating only spruce-fir as critical habitat and the effectiveness of the refugium restrictions.  Currently, red squirrels are found throughout the mixed-conifer and spruce-fir habitat zones, from about 2375 m (7800 ft.) on the north and east slopes to 3267 m (10,720) on High Peak.

The Mt. Graham red squirrel and the Pinaleño Mountains have been the center of considerable controversy since the 1980's due to the construction of The Mount Graham International Observatory on one of the highest peaks in the range.  Information on the facility and the controversy surrounding it is barely touched on in this web site.  We have, however, provided a few related links.

[Natural History]   [Pinaleño Mountains]    [Monitoring Project]   [Event Time Line]   [Bibliography]    [Related Links]

This site is maintained by the Mount Graham Biology Program - The University of Arizona

If you have any questions or comments please email us
Last updated November, 2006.