Press Release: New study finds politics, not science, led agency to lower goals for recovery of Mexican wolves

PRESS RELEASE: July 12, 2019
Contact: Carlos Carroll, (530) 628-3512, This email address is being protected from spambots. You need JavaScript enabled to view it.

New study finds politics, not science, led agency to lower goals for recovery of Mexican wolves.
Conclusions illustrate broad problems with recovery planning for wolves and other species.

In a new peer-reviewed study published in Scientific Reports, a journal of the Nature Publishing Group, researchers
have analyzed the science used by the US Fish and Wildlife Service to support its goals for recovery of the endangered Mexican wolf. The researchers found that politics inappropriately skewed development of criteria for recovery and delisting, a process which the Endangered Species Act requires to be solely based on scientific data. The study’s findings have broad implications for how agencies conduct endangered species recovery planning, especially for controversial species such as the wolf.

The Mexican wolf is the most endangered large mammal in North America. Because the current US wild population of 131 Mexican wolves descends from only 7 founders, the population faces severe threats from inbreeding and low genetic diversity, as well as other factors such as illegal killing. In 2013, a team of scientists convened by the Service developed draft Mexican wolf recovery criteria which proposed that a metapopulation totaling 750 wolves within the US would be necessary for recovery of the subspecies. These criteria were ultimately shelved after generating opposition from prominent politicians in southwestern US states. In 2017, new recovery criteria were developed with greater involvement by state representatives that called for less than half as many wolves (320) inhabiting a smaller portion of the southwestern states. A group of scientists decided to analyze whether the contrasting sets of goals could both be based on best-available science, as required by law.

The team of six researchers led by Dr. Carlos Carroll of the Klamath Center for Conservation Research included experts in genetics and population modeling, three of whom had served on one or more Mexican wolf recovery
teams. The scientists analyzed the population viability models which had informed development of both the 2013 and 2017 recovery criteria by forecasting the potential future for Mexican wolves. They found that the 2017 modeling process found smaller population goals were adequate for several reasons. The 2017 modeling team, which included state political appointees as well as scientists, chose optimistic values for threat factors such as disease risks without accounting for uncertainty in the data, increased the thresholds for what level of extinction risk and loss of genetic diversity was deemed “acceptable”, and assumed that many of the wild population’s wolf packs would continue to receive supplemental feeding even after delisting in order to counter continuing threats from genetic inbreeding and other factors. The authors describe why each of these decisions runs counter to best scientific practice or the Endangered Species Act. The study offers eight recommendations to strengthen scientific integrity and limit inappropriate political influence on endangered species recovery goals.

Summarizing the study’s findings, Dr. Carroll stated “Scientists often disagree, and our conclusions are not focused on which of the two models used the “best” estimate for specific threats such as disease. Instead, our results indicate that agencies need to account for uncertain data when crafting recovery criteria rather than assume the most optimistic outcome. We also demonstrate that many of the factors influencing the population model’s predictions are policy-based rather than scientific, and that the policy decisions embedded within the 2017 PVA are at odds with typical practice and the intent of the ESA.”

“Recovery goals based on politics rather than science slow Mexican wolf recovery by allowing the agency to forego opportunities to establish new populations in suitable habitat and to underestimate the number of wolves that need to be released from captivity into the wild population to improve genetic health. Such cases where political decisions are characterized as purely science-based should also concern us because they undermine scientific integrity and the transparent decision-making we expect from federal agencies” said Dr. Carroll.

Link to paper:


Dr. Carlos Carroll is an ecologist with the Klamath Center for Conservation Research, in Orleans, California. His research focuses on habitat, viability, and connectivity modeling for a diverse group of threatened and endangered species ranging from large carnivores to rare and endemic plant species. More information about his research can be found at