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Hualapai Mexican Vole Removed from List of Endangered Species Due to Erroneous Listing

By: Sarah C. Wells
06/28/17

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.

The Service listed the HMV as an endangered species approximately 30 years ago.  At that time, 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 the Service considered primary threats to be degraded 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 the HMV’s biology and life history requirements.

In 2004, the AGFD submitted to the Service a petition to delist the HMV.  The AGFD asserted that the original scientific data used at the time the Service classified the HMV as a subspecies were in error, and that the best scientific data available do not support the taxonomic recognition of the HMV as a distinguishable subspecies.  In May 2008, the Service reached an initial, positive “90-day finding” that the petitioned-for delisting of the Hualapai Mexican vole may be warranted.  However, the Service then initiated a periodic 5-year species status review for the HMV; the Service did not complete that species 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, in June 2015, the Service reached a positive “12-month” finding on the petition, concluding that the HMV warrants delisting and concurrently proposing a rule to delist.  Then, in December 2016, the Service reopened the public comment period for the proposed HMV delisting rule to remedy the Service’s failure to provide local newspaper notice of the rulemaking, as is required by the ESA.  Finally, following closure of the public comment period and the transfer of administrations, the Service has now issued the final HMV delisting rule.  The petition process for the Hualapai Mexican vole spanned over thirteen years from start to finish, whereas the ESA provides a maximum of two years for the entirety of the ESA petition and rulemaking process.

The Service’s approach to the HMV delisting is important beyond the outcome for this single taxon.  The reasoning provides a window into how the Service may consider the continued listing of the many species for which limited information was available at the time of listing and currently-available information is viewed by some as inconclusive.  Here, the Service recognizes that various analyses and reviews undertaken since the HMV’s listing “present multiple interpretations of the taxonomy and distribution of Mexican voles in Arizona, none of which correlates to that of our original listing.”  Yet the Service concludes that, although the best available information presents conflicting information on the taxonomy of Mexican voles in general, it no longer supports the recognition of a separate HMV subspecies, and this level of agreement is sufficient for delisting.  The preamble to the final rule includes a telling Service response to a peer reviewer in favor of a more cautious approach to the delisting determination.  The reviewer states, “The Service should conduct a detailed study and analysis of the vole’s genetics prior to taking any action to reclassify the subspecies.  Conflicting data on genetics should be resolved prior to agency action and should not be used as a justification to delist.”  The Service response reiterates the Service’s statutory obligation to base its action on a petition on a thorough review of the best available scientific and commercial data, which here indicates listing in error.  Importantly, the Service asserted its authority to rely on the best available data and rejected a measure of uncertainty as a basis for continued listing where the best available data indicates listing is not warranted.


Disclosure:  Nossaman represented American Stewards of Liberty and Mohave County, Arizona, in efforts to delist the HMV and continues to represent the American Stewards in petitions to delist other species for which original listing was in error.

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