The Tucson-based Center for Biological Diversity has sued the U.S. Fish and Wildlife Service to protect the endangered Mount Graham red squirrel.

The squirrel is found in the higher elevations of a southeastern Arizona mountain, where it has lived for thousands of years.

The Center for Biological Diversity says that structures on the mountain, from cabins to a University of Arizona observatory, have interfered with recovery.

The number of squirrels fluctuates, but the center maintains it is still too low.

“The problem that we have now is, is that the habitat that’s protected officially, called critical habitat, doesn’t protect the squirrels, because essentially none live there,” said Robin Silver, a spokesman for the center.

Silver said that climate change, wildfire and forest management have nearly eliminated the squirrel’s best habitat, forcing it into lower elevations.