Give the Mexican Gray Wolf a Scientific Recovery Plan!

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We applaud the efforts that the USFWS and its partners have put into recovering the critically imperiled Mexican Gray Wolf (Canis lupus baileyi). However, we have serious concerns over the recently adopted Mexican Wolf Recovery Plan (MWRP). Listed below are just three of our many worries:

Under the MWRP, the range of the Mexican Gray Wolf would be restricted to south of Interstate 40 (I-40). The argument for this range restriction is that the subspecies is not native to north of I-40, and a single morphology-based study, Heffelfinger et al. (2017), is used to justify this conclusion (USFWS 2017a, USFWS 2017b). However, genetics-based studies have found that the Mexican Gray Wolf is part of a Southern Gray Wolf clade and that haplotypes from this clade have been found in historical wolves that lived as far north as Colorado and Utah; this genetic evidence suggests that the historical range of the Mexican Gray Wolf has been underestimated (Leonard et al. 2005; NCEAS 2014; Hendricks et al. 2016). In addition, suitable habitat exists for Mexican Gray Wolves in the Grand Canyon Ecoregion and the Southern Rocky Mountains, which have been recommended as reintroduction sites for the subspecies (Wayne & Hedrick 2011; Carroll et al. 2014). Scientists have previously criticized the restricted range as unscientific (NCEAS 2014), and in the peer reviews to the MWRP, the I-40 range restriction and the heavy reliance on Heffelfinger et al. (2017) to define historical range have been criticized (USFWS 2017c). Mexican Gray Wolves should not have their range restricted, and reintroductions should be considered in the Grand Canyon Ecoregion and the Southern Rocky Mountains.

Under the MWRP, the recovery goal for the Mexican Gray Wolf is 320 in the USA and 200 in Mexico, for a total population size of 520 wolves distributed between two populations; genetic connectivity between these two populations is not a required criteria for recovery. In addition, a population cap of 380 in the USA is recommended (USFWS 2017a). The recovery goal is too low to ensure the survival of the Mexican Gray Wolf and contradicts recent scientific findings, which suggest that at least 750 wolves distributed among three interconnected populations are required to recover the subspecies; genetic connectivity between populations is vital for recovery (Wayne & Hedrick 2011; Carroll et al. 2014). The USFWS should either adopt this science-based suggestion as the recovery goal or use this recommendation as a basis to conduct further research into a scientifically viable recovery goal. In addition, the USFWS should completely eliminate the population cap, as this is unnecessary, unscientific, and unethical.

Under the MWRP, one of the recovery criteria is that the Mexican Gray Wolf population has a 90% probability of persistence over 100 years (USFWS 2017a). While this sounds like a viable goal, this would mean that the subspecies has a 10% probability of extinction. Under the criteria for the IUCN Red List of Threatened Species, a 10% probability of extinction over 100 years would qualify a species as Vulnerable (VU), which is defined as "facing a high risk of extinction in the wild" (IUCN 2012). If the Mexican Gray Wolf qualifies as VU under the IUCN Red List of Threatened Species when it meets the "recovery" goals, then it is not truly recovered and is still at risk of extinction. The goal of any recovery plan should be to fully recover a species, not to place it into a less severe threatened category. The USFWS should revise this recovery criteria to better reflect what qualifies as a healthy population under the IUCN Red List of Threatened Species criteria.

The purpose of the Endangered Species Act (ESA) is stated as “to provide a program for the conservation of… endangered species” (Congress 1973), with the ESA defining an Endangered species as “any species which is in danger of extinction throughout all or a significant portion of its range” (Congress 1973). The Mexican Gray Wolf is listed as Endangered under the ESA, and as such the USFWS is obligated to protect and recover the subspecies (Congress 1973; USFWS 2017a). The recently adopted MWRP may be a violation of the ESA since it would provide inadequate conservation actions for the Mexican Gray Wolf, and under a worst-case scenario, it could potentially result in the extinction of this Endangered subspecies.

We ask that you please revise the MWRP so that it better reflects the science of what is necessary to recover the Mexican Gray Wolf.


Carroll, C., R. Fredrickson, & R. C. Lacy. 2014. Developing metapopulation connectivity criteria from genetic and habitat data to recover the endangered Mexican wolf. Conservation Biology 28: 76 – 86.

Heffelfinger, J. R., R. M. Nowak, & D. Paetkau. 2017. Clarifying historical range to aid recovery of the Mexican wolf. The Journal of Wildlife Management 81: 766 - 777.

Hendricks, S. A., P. R. S. Clee, R. J. Harrigan, J. P. Pollinger, A. H. Freedman, R. Callas, P. J. Figura, & R. K. Wayne. 2016. Re-defining historical geographic range in species with parse records: implications for the Mexican wolf reintroduction program. Biological Conservation 194: 48 – 57.

IUCN. (2012). IUCN Red List Categories and Criteria: Version 3.1. Second Edition. Gland, Switzerland and Cambridge, UK: IUCN. Iv + 32pp.

Lenk, H. 2017. Struggle for existence: Mexican gray wolves in the American Southwest. BS thesis. Arizona State University, Tempe, Arizona.

Leonard, J. A., C. Vila, & R. K. Wayne. 2005. Legacy lost: genetic variability and population size of extirpated US grey wolves (Canis lupus). Molecular Ecology 14: 9 – 17.

NCEAS (National Center for Ecological Analysis and Synthesis). 2014. Review of proposed rule regarding status of the wolf under the Endangered Species Act. University of California.

US Congress. 1973. Endangered Species Act. 16 U.S.C. <>

USFWS (United States Fish and Wildlife Service). 2003. Endangered and threatened wildlife and plants; final rule to reclassify and remove the gray wolf from the list of endangered and threatened wildlife in portions of the conterminous United States; establishment of two special regulations for threatened gray wolves.

USFWS (United States Fish and Wildlife Service). 2017a. Mexican wolf recovery plan, first revision.

USFWS (United States Fish and Wildlife Service). 2017b. Biological report for the Mexican wolf (Canis lupus baileyi).

USFWS (United States Fish and Wildlife Service). 2017c. Comments on the draft biological report (May 1, 2017) for the Mexican wolf (Canis lupus baileyi).

Wayne, R., & P. Hedrick. 2011. Genetics and wolf conservation in the American west: lessons and challenges. Heredity 107: 16 – 19.