The Pacific pocket mouse (Perognathus longimembris pacificus) is a small brownish rodent endemic to coastal southwestern California. Historically, the Pacific pocket mouse range (Map: current, historical) once extended from Los Angeles County south to the Mexican border. Pocket mice are only found within 4 kilometers of the coast on finegrained sandy substrates in coastal sage scrub, coastal strand, and river alluvium. The species remains one of the most endangered animals in the United States.

The Center for Biological Diversity, Endangered Habitats League and Natural Resources Defense Council have petitioned the United States Fish and Wildlife Service to revise its critical habitat determination for the Pacific pocket mouse and designate critical habitat pursuant to the federal Endangered Species Act.

When the Service listed the Pacific pocket mouse as an endangered species in 1994, it declined to designate critical habitat, determining that to do so would not be “prudent.” Specifically, the Service concluded that designating critical habitat for the Pacific pocket mouse (1) would lead to an increased threat to the species through the publication of maps identifying the location of the sole Pacific pocket mouse population then known to exist; and (2) would not provide any conservation benefit to the species because the only population then known was located on private property that lacked a “federal nexus” subjecting it to the critical habitat provisions of the ESA. These conclusions can no longer be justified.

Since 1994 two additional Pacific pocket mouse populations have been discovered. These are located on Camp Pendleton, a Marine Corps base to which access is strictly controlled. More importantly, the exact location of the Camp Pendleton populations -- as well as the exact location of the single population that was known to exist in 1994 -- have long since been made public in numerous published environmental surveys. Accordingly, designating critical habitat for the Pacific pocket mouse would not lead to any increased threat to the species. Designating critical habitat for the Pacific pocket mouse would however provide significant additional conservation benefits to the species.

The Camp Pendleton populations are subject to a variety of threats, including construction of a six-lane toll road and Marine Corps operations. The ESA prohibits federal agencies from carrying out, funding or permitting activities which result in the adverse modification of designated critical habitat. Once critical habitat is designated for the Pacific pocket mouse, the Marine Corps will be required to ensure that its operations will not adversely modify any habitat essential to the mouse’s survival. The Federal Highways Administration has jurisdiction over the proposed toll road and operates under the same obligation. The Service has also changed its policy regarding the designation of critical habitat on private property with no apparent federal nexus. The Service now regularly designates critical habitat on private property regardless of whether that property is currently subject to a federal nexus bringing it within the ambit of the ESA.

What you can do:

Send a letter supporting designation of critical habitat: Hon.
Gale Norton, Secretary of the Interior, Main Interior Building, 18th and
C Streets, N.W., Washington, D.C. 20240