Two rare Arizona cactuses have been added to the federal list of endangered species. The designation by the United States Fish and Wildlife Service came ahead of the partial shutdown of the federal government. A settlement with the Center for Biological Diversity required the agency to speed protection decisions for 757 species across the country. The Acuna cactus is found on small knolls and gravel ridges in desert areas of Maricopa, Pima and Pinal counties. The plants are threatened by drought, climate change, predation and invasive species. The Fickeisen plains cactus is more rare and found in Coconino and Mohave counties. The rounded, quarter-sized cactus retracts below ground in the winter and summer.