TUCSON, Ariz.— The Center for Biological Diversity and Maricopa Audubon sued the U.S. Fish and Wildlife Service today for failing to protect habitat essential to the survival and recovery of southeast Arizona’s Mount Graham red squirrels. These squirrels are the most endangered terrestrial animal in the United States.

Today’s lawsuit, filed in U.S. District Court in Tucson, said the Service has unlawfully delayed updating the squirrels’ critical habitat in response to a 2017 petition, violating the Endangered Species Act.

“It’s pathetic that the Fish and Wildlife Service recognized these squirrels were in jeopardy more than two decades ago but now ignores this when there are fewer squirrels and less habitat,” said Robin Silver, cofounder of the Center for Biological Diversity. “The squirrel’s situation is now even more dire as they face a historic habitat bottleneck, isolated in tiny islands of mature canopied forest that are widely separated from each other. This greatly increases predation risks and the likelihood that these squirrels will go extinct.”

Mount Graham red squirrels live only in the Pinaleño Mountains, an isolated “sky island” range in southeastern Arizona. Nearly all the squirrels now live outside the currently designated critical habitat areas, which only include spruce-fir forests above 9,200 feet elevation. The squirrels’ original critical habitat was destroyed by construction of mountaintop telescopes, wildfires and fires set unnecessarily to protect the telescopes. A census from the fall of 2023 found just 144 squirrels.

In December 2017 the Center and Maricopa Audubon petitioned the Service to update the squirrels’ critical habitat to include lower-elevation, mixed-conifer forests where the squirrels are now living. Those forest areas were not included in the original 1990 critical habitat designation since at that time most squirrels lived in spruce-fir forests at the mountain’s highest elevations.

The groups sued in April 2019 and again in November 2020 to compel the agency to expand the habitat, but so far the agency has failed to act, violating the Endangered Species Act.

Today’s lawsuit follows on the heels of a U.S. District Court magistrate judge’s recommendation last month that the Service redo its biological analysis for the Mount Graham area recreational summer cabins and summer camp. Both developments are located outside of the currently protected habitat and in the only canopied forest habitat available for short-term restoration.

“The Fish and Wildlife Service is refusing to restore the only habitat available for these squirrels because they’re afraid to inconvenience a few renters by moving their recreational structures to other locations,” said Charles Babbitt, conservation chair of Maricopa Audubon. “The most extensive amount of surviving mature canopied forest that can be restored quickly should be protected so the squirrels can survive and thrive.”