The small nocturnal squirrel is only found in higher elevations of West Virginia and one county in Virginia. The U.S. Fish and Wildlife Service removed it from the list under the Bush Administration after a count found 1,200 of the animals. That was up from 10 animals spotted in 1985.
The groups say they filed the lawsuit because they claim the agency did not follow its own recovery plan for the species. They're also concerned that the squirrels' habitat is now in danger of development.
The Department of Interior declined to comment on the litigation.
