TUCSON, Ariz.— The Center for Biological Diversity and Maricopa Audubon today filed a notice of intent to sue the U.S. Fish and Wildlife Service to expand critical habitat for Arizona’s highly endangered Mount Graham red squirrels.

The squirrels live only in the Pinaleño Mountains, an isolated “sky island” range in southeastern Arizona. Only about 78 remain on Earth.

The squirrels’ current designated critical habitat includes only spruce-fir forests above 9,200 feet. Telescope construction, wildfires and fires set unnecessarily to protect the telescopes have pushed the squirrels to lower elevations and mixed-conifer forests that lack official habitat designation. Hotter, drier conditions from climate change are also believed to be harming the squirrels.

In December 2017 the Center and Maricopa Audubon petitioned the Service to expand the critical habitat to include lower-elevation, mixed-conifer forests. The agency was required to issue a one-year finding in response to the 2017 petition but has failed to do so.

“For almost three years, Fish and Wildlife Service officials have done nothing to protect the habitat crucial for the squirrel to survive,” said Robin Silver, a Center cofounder. “With so few Mount Graham red squirrels left, this lack of action is inexcusable. Every day the agency delays is another day the red squirrels are pushed closer to extinction.”

One challenge for the squirrel is that the best remaining habitat is occupied by a Forest Service-owned camp and recreational cabins in the Columbine area. These were supposed to have been removed to mitigate the damage caused by the telescope construction. The Center and Maricopa Audubon filed suit June 10 to force the removal of the structures. The Columbine area contains the only surviving habitat that can be restored in the short term to help the severely endangered squirrel.

“After widespread loss of their homes to the telescopes and fire, the squirrels desperately need new habitat protection,” said Mark Larson, Maricopa Audubon president.