Mount Graham Red Squirrel

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Mount Graham Red Squirrel

Tamiasciurus hudsonicus grahamensis

Status	Endangered
Listed	June 3, 1987
Family	Sciuridae (Squirrels)
Description	Grayish brown tree squirrel.
Habitat	Mountain woodlands.
Food	Conifer seeds.
Reproduction	Litter of one to seven young.
Threats	Limited range, logging, construction.
Range	Arizona

Description

The Mount Graham red squirrel, Tamiasciurus hudsonicus grahamensis, is grayish brown, tinged with rust or yellow on the back, and has a dark lateral line separating the lighter underparts from the darker sides. The tail is bushy, and the ears are slightly tufted in winter. Average body length is about 8 in (20 cm); average tail length is 5 in (14 cm). This squirrel differs from the common red squirrel (Tamiasciurus hudsonicus ) by having a smaller body and shorter tail. The common red squirrel is found in Canada, Alaska, and northern and western states.

Behavior

The Mount Graham red squirrel is a tree squirrel. Although it has not yet been closely studied, similar squirrels produce one or two litters per year after a gestation period of 40-45 days. Litter size is from one to seven, and the young are born blind. This species feeds primarily on conifer seeds. It does not hibernate, but during the winter relies on caches of stored seeds, known as middens. Middens are built up in cool, moist places such as crevices, hollow logs, and stumps.

Habitat

The squirrel's preferred habitat is in higher altitude (above 10,000 ft (3,050 m) stands of mature Engelmann spruce and corkbark fir. It also inhabits mixed-conifer and spruce-fir habitat zones, from elevations of about 7,800 ft (2,380 m) on the north and east slopes to 10,720 ft (3,270 m) on High Peak.

Distribution

The Mount Graham red squirrel has historically been found only in the Pinaleno Mountains of Graham County in southeastern Arizona.

The current range of the Mount Graham squirrel falls entirely within the Safford Ranger District of the Colorado National Forest. A survey of middens in 1986 yielded a population estimate of about 320 animals. The count for 1987 (the first year of an annual survey) was approximately 245 individuals, down 25 percent. The drop in population was due to a poor spruce cone crop. Based on counts of active middens in 1988, the squirrel population had declined to about 215. The 1990 survey showed a possible rise in the population again, with an estimation, including juveniles, of between 250 and 300 animals.

Since 1989, biologists have discovered that, while the squirrel was once thought to inhabit only the spruce-fir habitat on the Pinaleno range 1700 acres (690 hectares) of the highest elevations (10,000 ft (3,050 m) which have been designated as critical habitat and are managed by the U.S. Forest Service—the species range dips far below these heights. Significant red squirrel populations have been found at lower elevations on the mountains. A census in the fall of 1993, found about 55% of the total population in this zone, with about 25% in the spruce-fir zone and 20% in the mixed-conifer zone.

Threats

This species was common within its range around the turn of the century but was declining by the 1920s, and rare by the 1950s. The major cause of its decline was the loss of forest habitat caused by logging. Most accessible stands of mature timber had been cut by 1973. Further harvesting of trees could eliminate remaining habitat; however, the squirrel's listing as an Endangered Species set in motion the designation of 1,700 acres (690 hectares) as critical habitat, managed by the Forest Service, with restricted access for outsiders. The Mount Graham red squirrel also suffers from competition with the introduced tassel-eared squirrel (Sciurus aberti ).

In the late 1980s and early 1990s, there was some concern that the construction of the Mount Graham International Observatory, a large astrophysical observatory complex of the University of Arizona within the squirrel's range, would seriously threaten the remaining populations. The squirrel was listed in 1987 (over objections from the University of Arizona), and Congress approved the observatory building permit in 1988, though the university was required to work with conservationists to protect the squirrel.

Conservation and Recovery

To fulfill the terms of its permit, the University funds a monitoring program to determine the extent of the construction project's impact on the squirrel population (so far, two telescopes are in operation and construction continues). Five biologists are on staff to monitor the red squirrel population around the observatory site, and so far there have been no indications of a negative impact caused by the ongoing construction.