On June 23, 2017, the U.S. Fish and Wildlife Service (Service) promulgated a long-awaited final rule to delist the Hualapai Mexican vole (Microtus mexicanus hualpaiensis) (HMV) due to the Service’s determination that the original 1987 listing of the HMV under the Endangered Species Act (ESA) was in error. Based upon more recent scientific and commercial information, the Service concluded that the HMV is not a distinguishable subspecies of Mexican vole and thus is not a valid taxonomic entity listable under the ESA. This error in taxonomic classification was first raised by a delisting petition filed in August 2004 by the Arizona Game and Fish Department (AGFD). The delisting goes into effect on July 24, 2017.

When the Service listed the HMV as endangered approximately 30 years ago, the Service considered the HMV to be one of three subspecies of Mexican vole found in Arizona. The Service believed the HMV occupied an extremely restricted range within only the Hualapai Mountains of Arizona and listed the HMV based on perceived threats posed by degradation of habitat due to drought, livestock grazing, and human recreation. The Service’s 1991 Recovery Plan for the HMV outlined management and research priorities but included no recovery criteria due to the lack of information on HMV biology and life history requirements.

In 2004, the AGFD petitioned the Service to delist the HMV. The AGFD asserted that the original scientific data used to classify the HMV as a subspecies were in error, and that the best scientific data currently available do not support the taxonomic recognition of the HMV as a distinguishable subspecies. Following the Service’s May 2008 positive “90-day finding” that the petitioned-for delisting of the HMV may be warranted, the Service then initiated a periodic 5-year species status review for the HMV; the Service did not complete the status review or the requisite “12-month” finding on the delisting petition. Following years of apparent Service inaction on the HMV petition, in January 2015, Mojave County, Arizona, and the non-profit private property rights group American Stewards of Liberty filed a 60-day notice of intent to sue the Service for failure to reach a timely 12-month finding on the HMV delisting petition. Approximately six months later, the Service issued a positive “12-month finding” on the petition and concurrently proposed a rule to delist the HMV. Following the Service’s December 2016 reopening of the public comment period for the proposed rule to remedy a procedural error, the Service has now issued the final HMV delisting rule. Overall, the delisting petition process for the HMV spanned nearly thirteen years, although the ESA establishes a maximum of two years for the entirety of the ESA petition and rulemaking process.