Gray Wolves Under the Endangered Species Act (ESA):Distinct Population Segments and Experimental Populations

Kristina Alexander
Legislative Attorney

M. Lynne Corn
Specialist in Natural Resources Policy

After near eradication of the gray wolf from the lower 48 states in the first half of the 20th century, the wolf was on the Endangered Species Act’s (ESA’s) first list of endangered species, divided into two subspecies—the Eastern Timberwolf and the northern Rocky Mountain wolf. In 1978 the wolf was listed at the species level (the gray wolf) as endangered in all of the conterminous 48 states except Minnesota, where it was listed as threatened. With the exception of experimental populations established in the 1990s, in which the U.S. Fish and Wildlife Service (FWS) reintroduced wolves to selected areas, protections for the gray wolf have diminished as wolf populations have increased in some areas—such as in the Northern Rocky Mountains. The use of distinct population segments (DPSs), a term created in the 1978 ESA amendments, has played a role in that reduced protection. DPSs allow vertebrate species to be divided into distinct groups, based on geography and genetic distinctions. This report analyzes the DPS designation process as it is applied to the gray wolf. It also examines experimental populations of wolves under the ESA.

Experimental populations (Ex Pops) of wolves were reintroduced in three regions in the United States in the 1990s: Central Idaho, Yellowstone, and Blue Range (in Arizona and New Mexico, known as Mexican gray wolves). The Ex Pops in Central Idaho and Yellowstone have grown to over 1,650 wolves as of December 31, 2010, while the Mexican gray wolf population has not surpassed 59 wolves, and as of January 2011 totaled 50.

ESA protection for wolf DPSs has changed back and forth since the first DPSs—Western, Eastern, and Southwestern—were proposed in 2003. Each effort by FWS to delist the wolf or designate a DPS has been rejected by a court. In 2003, FWS determined that because of the population size, the Western and Eastern DPSs no longer needed the protection of the ESA and so those DPSs were downlisted from endangered to threatened. Courts nullified the rulemaking. In 2007, FWS designated and delisted the Western Great Lakes DPS, and in early 2008, FWS designated and delisted the Northern Rocky Mountain DPS. However, courts found both delistings flawed and vacated both rulemakings. In April 2009, FWS again established DPSs in the Western Great Lakes and the Northern Rockies and delisted both populations except for in Wyoming. FWS settled the suit regarding the Western Great Lakes delisting, returning the population to its previous status (threatened and endangered). In August 2010, a court ruled that the Northern Rockies delisting violated the ESA, directing that the delisting be declared invalid. The Northern Rockies wolves were returned to their experimental population status, meaning they were treated as threatened in most circumstances but were endangered outside of the Ex Pop boundaries.

A March 2011 conditional settlement agreement would have ended lawsuits by the participating plaintiffs about Northern Rocky Mountains DPSs for at least five years, but it fell through when a court ruled it lacked the authority to reinstate part of the 2009 DPS rule. Days after the agreement collapsed, Congress passed a law (P.L. 112-10) directing FWS to reissue the 2009 DPS rule. Section 1713 of P.L. 112-10 required FWS to reissue the 2009 Northern Rockies DPS rule within 60 days of April 15. This law ends federal protection of the gray wolf in Montana, Idaho, eastern Washington, eastern Oregon, and north-central Utah, but keeps the wolf as a listed species in the rest of the lower 48 states. The Federal Register notice was issued May 5, 2011.

Also in April, FWS announced it would delist the gray wolf in the Western Great Lakes area, and announced a new species of wolf, the eastern wolf (Canis lycaon).


Date of Report: May 5, 2011
Number of Pages: 26
Order Number: RL34238
Price: $29.95

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