The Mt. Graham Red Squirrel
Monitoring Program

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The Mount Graham red squirrel (MGRS) is an endangered subspecies found only in the Pinaleño Mountains of Graham County, southeastern Arizona.  Reported to be extinct in the 1960s, the squirrel was rediscovered in 1972 and listed as endangered in 1987.

The Arizona-Idaho Conservation Act was passed in 1988, which allowed the construction of an astrophysical observatory on the Pinaleņo Mountains within MGRS habitat.  As a result, the University of Arizona, one of the financial supporters of the observatory, is required to fund a monitoring program responsible for determining whether or not construction of the Mount Graham International Observatory (MGIO) is having any negative impact on the squirrel population.  The MGRS Monitoring Program, a separate entity from the Observatory, keeps track of the red squirrel population within 300 m of the observatory and access road. In addition, two non-construction areas are monitored for comparison as control groups.

The monitored area, (originally 326 ha) is divided into two habitat types: mixed-conifer forest and spruce-fir forest.  The mixed-conifer forest is located below 3050m elevation and is composed primarily of Douglas-fir (Pseudotsuga menziesii), corkbark fir (Abies lasiocarpa var. arizonica), Engelmann spruce (Picea engelmannii), ponderosa pine (Pinus ponderosa), white pine (Pinus strobiformis), and aspen (Populus tremuloides).  The spruce-fir is higher in elevation than the mixed-conifer forest and is dominated by Engelmann spruce and corkbark fir. This portion of the Mt. Graham red squirrel population has been monitored since 1989 and has ranged in size from 27 to 229 individuals.  Fire damage, insect outbreaks, weather fluctuations and variation in food resources have occurred during the course of study.

The Mt. Graham Red Squirrel Monitoring Program is continuously analyzing ecological data that has been collected throughout the course of the project. Several manuscripts have been published and there are always more in the works.

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