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

The wolf was nearly eradicated from the lower 48 states in the first half of the 20th century. In 1974 U.S. Fish and Wildlife Service (FWS) placed gray wolf subspecies, the eastern timber wolf, the Mexican wolf, and the northern Rocky Mountain wolf, on the Endangered Species Act’s (ESA) first list of endangered species. In 1978 FWS replaced the subspecies listings by listing the gray wolf species (Canis lupus) as endangered in all of the conterminous 48 states except Minnesota, where FWS listed it as threatened. In 2011 FWS found that this listing was in error; that more targeted regional units were appropriate for wolves (notably in the Southwest and Pacific Northwest); that a newly recognized species, the eastern wolf (Canis lycaon), not the gray wolf, occupied the Northeast; and that all or parts of 29 eastern states should be removed from the gray wolf’s historic range.

With the exception of experimental populations (Ex Pops) of gray wolves that FWS established in order to reintroduce wolves to selected areas, protections for the gray wolf have diminished as wolf populations have increased in areas such as the Northern Rocky Mountains. The use of distinct population segments (DPSs), a term created in the 1978 ESA amendments, has played a role in reduced protection. Through DPSs, vertebrate species may be divided into distinct groups, based on geography and genetic distinctions for listing purposes.

Ex Pops of wolves were reintroduced in three regions of the United States in the 1990s: Central Idaho, Yellowstone, and the Blue Range of Arizona and New Mexico. 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 of the Blue Range has not surpassed 59 wolves, and as of January 2011 totaled 50.

ESA protection for wolf DPSs has varied 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 or settled by the agency. Most recently, the April 2009 rules that had established and then delisted DPSs in the Western Great Lakes and the Northern Rockies were nullified as a result of litigation. As a consequence, the Northern Rockies wolves resumed their Ex Pop status, meaning they were treated as threatened in most circumstances but were endangered outside of the Ex Pop boundaries. Wolves in the rest of the lower 48 states were again endangered, with the exception of Minnesota wolves, which were threatened.

The April 2009 rule for the Northern Rockies was the topic of legislation in April 2011, when Congress took the unusual step of directing FWS to delist an endangered species. Section 1713 of P.L. 112-10 required FWS to reissue the 2009 Northern Rockies DPS rule. FWS’s reissuance of that rule on May 5, 2011, ended federal protection of the gray wolf in Montana, Idaho, eastern Washington, eastern Oregon, and north-central Utah, but kept the wolf as a listed species in the remainder of the lower 48 states. Also on May 5, 2011, FWS proposed designating a DPS in the Western Great Lakes area and delisting those gray wolves. On October 5, 2011, FWS proposed delisting the wolves in the Wyoming DPS and terminating the Ex Pop. The proposal is contingent upon the Wyoming legislature’s passing certain management requirements.

This report analyzes the ESA as it applies to gray wolves and, in particular, Ex Pops and DPSs.


Date of Report: November 1, 2011
Number of Pages: 34
Order Number: RL34238
Price: $29.95

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