Order Code RL34238
Gray Wolves Under
the Endangered Species Act: Distinct Population
Segments and Experimental Populations
November 5, 2007
Kristina Alexander
Legislative Attorney
American Law Division
M. Lynne Corn
Specialist in Natural Resources Policy
Resources, Science, and Industry Division

---

Gray Wolves Under the Endangered Species Act:
Distinct Population Segments and
Experimental Populations
Summary
The wolf was among the first animals protected under the Endangered Species
Preservation Act, a predecessor to the current Endangered Species Act (ESA). In
1978 the gray wolf was listed 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, the protections for the gray wolf
have been diminishing since that date, as wolf populations have increased in some
areas. 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
distinction. In 2007 the wolf was removed from the endangered species list for most
of its range, based on two DPSs — the Northern Rocky Mountains and the Western
Great Lakes. This report looks at the DPS process as it is applied to the gray wolf.
It also reviews experimental populations of wolves under the ESA and their
protections.

---

Contents
Background and Regulatory History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Wolf Populations: A Taxonomic View . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Species and Distinct Population Segments . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Regulatory History of Distinct Population Segments . . . . . . . . . . . . . . 5
Pros and Cons of Distinct Population Segments . . . . . . . . . . . . . . . . . . 6
Gray Wolf Distinct Population Segments . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Litigation Regarding Western and Eastern DPSs . . . . . . . . . . . . . . . . . 8
Experimental Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Experimental Populations of Gray Wolves . . . . . . . . . . . . . . . . . . . . . . . . . 10
Yellowstone Litigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Southwest Litigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Section 4(d) Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Section 4(d) Rules for Gray Wolves . . . . . . . . . . . . . . . . . . . . . . . . . . 12

---

Gray Wolves Under
the Endangered Species Act:
Distinct Population Segments and
Experimental Populations
Background and Regulatory History
The history of gray wolf protection is interconnected with the history of the
Endangered Species Act (ESA) (16 U.S.C. §§ 1531- 1543). Gray wolf protection
began at the nascency of the ESA, when it was one of the first species covered under
the Endangered Species Protection Act of 1966.1 As the ESA has been amended, so
has gray wolf protection. The act provides the basis for determining which species
are threatened and endangered, and how those listed species will be protected.
Amendments allow consideration of distinct groups within species for protection.
The act allows introduction of experimental populations to areas where the species
no longer exists, and provides regulatory protections for that introduction. Each of
these elements will be discussed in this report generally, and more specifically in the
context of gray wolf protection.
For centuries, wolf populations have been under attack by humans. The effort
to reduce or eliminate the species was designed to protect humans from a perceived
direct threat to humans or to protect livestock or favored game species. Wolves were
eventually eliminated in most states in an effort supported by the science community
at the time. But coinciding roughly with the forester Aldo Leopold’s essay “Killing
the Wolf” in A Sand County Almanac in 1948, this view began to change. Leopold
wrote:
I was young then, and full of trigger-itch; I thought that because fewer wolves
meant more deer, that no wolves would mean hunters’ paradise. But after seeing
the green fire die, I sensed that neither the wolf nor the mountain agreed with
such a view.... Since then I have lived to see state after state extirpate its wolves.
I have watched the face of many a newly wolfless mountain, and seen the
south-facing slopes wrinkle with a maze of new deer trails. I have seen every
edible bush and seedling browsed, first to anaemic desuetude, and then to death.
In 1967, when the gray wolf was listed under the first version of the Endangered
Species Act, it was listed in two subspecies, the eastern timber wolf, and the northern
1 P.L. 89-669, 80 Stat. 926 (October 15, 1966).

---

CRS-2
Rocky Mountain wolf.2 In 1978 the gray wolf was relisted as endangered at the
species level throughout the lower 48 states, with the exception of Minnesota, where
it was listed as threatened.3 In the 1990s actions were taken to reintroduce the wolf
into areas where it had been eradicated. Experimental populations were introduced
into the Yellowstone area and central Idaho,4 and in Arizona, New Mexico and
Texas.5 Efforts to protect the wolf have always been controversial, however. The
Fish and Wildlife Service (FWS) reports receiving, and denying, “several petitions”
to delist the wolf in all or part of the 48 states.6 Additionally, in 1987 legislation was
introduced to remove the gray wolf from the ESA protected list.7 The amendment
failed.
Wolf Populations: A Taxonomic View
Like many large mammals, such as bears (Ursus arctos), mountain lions (Felis
concolor), and white-tailed deer (Odocoileus virginianus), gray wolves (Canis lupus)
have a complicated, even convoluted, taxonomic history. Variations in color, size,
and bone structure have led some mammalogists to name wolves in various areas as
different subspecies or populations, where other credible experts would see only a
single species with variability. Here are scientific definitions of a few key terms:
! A population is a group of “organisms of the same species that
inhabit a specific area.”
! A species is a “naturally [occurring] population or a group of
potentially interbreeding populations that is reproductively isolated
(i.e., cannot exchange genetic material) from other such populations
or groups.”
! A subspecies is a “taxonomic category that subdivides species into
morphologically distinct groups of individuals representing a step
toward the production of a new species, although they are still fully
capable of interbreeding. Subspecies are usually geographically
isolated.”
! Taxon, or the plural taxa, is defined as: “a grouping of organisms
given a formal taxonomic name at any rank: species, genus, family,
order, class, division, phylum, or kingdom.”8
2 The first list of endangered species included the timber wolf (Canis lupus lycaon) and the
red wolf (Canis niger, now called Canis rufus). 32 Fed. Reg. 4001 (March 11, 1967).
3 43 Fed. Reg. 9607 (March 9, 1978).
4 59 Fed. Reg. 60252 (November 22, 1994).
5 63 Fed. Reg. 1752 (January 12, 1998).
6 68 Fed. Reg. 15803, 15807 (April 1, 2003).
7 The proposed legislation would have amended an authorizations act to fund the ESA.
H.Amdt. 576 (100th Congress): “(b) Exception to Listing. — Upon enactment of this
subsection of this Act, the gray wolf, Canis Lupus, shall not be considered an endangered
or threatened species under the Endangered Species Act of 1973.”
8 All the definitions are from Henry W. Art (ed.), The Dictionary of Ecology and
(continued...)

---

CRS-3
These terms may appear clear; however, there are no simple measures to draw
unequivocal distinctions. Biologists commonly divide their colleagues into
“lumpers” and “splitters,” based on their inclinations in classifying organisms. As
the names suggest, lumpers are those who tend to minimize differences, and see one
or a few species, perhaps with some variations, while splitters would tend to
emphasize those differences, dividing a species into many subspecies, or populations.
For wolves, which are (or were) found in temperate and polar areas throughout the
Northern Hemisphere, some observers (splitters) would argue that there are as many
as 24 subspecies in North America and eight in Europe and Asia.9 More recently,
lumpers have had the upper hand, and FWS recognizes two species (gray and red
wolves), and divides the gray wolf into six “distinct population segments,” based in
part on administrative and procedural criteria.10
While confusing to the non-scientist, this muddled state of taxonomic affairs is
entirely predictable for several reasons. First, wolves are extremely wide-ranging,
both as a species and as individuals, so interbreeding among them could certainly
muddy the picture. Second, the consistency of variations over time is hard to
determine, since long-range studies of long-lived species are rare. Third,
evolutionary change does not stop, and wolves are an adaptable species, as shown by
their behavior and by their presence in a tremendous variety of ecosystems.11 If FWS
scientists’ choice of state boundaries to delineate wolf populations is criticized as
arbitrary, the debate among academic scientists also has an air of informed judgment
— and there is no reason to predict that either debate will end any time soon.

Species and Distinct Population Segments
If the scientific community is somewhat inconsistent on its identification of
species, the law has fared no better. The ESA definition of species has changed since
the early days of the act. In 1973 the definition included “any subspecies of fish or
wildlife or plants and any other group of fish or wildlife of the same species or
smaller taxa in common spatial arrangement that interbreed when mature.”12 In 1978
8 (...continued)
Environmental Science (New York: Henry Holt and Co. 1993).
9 See discussion, citing various authors, in L. David Mech, The Wolf: The Ecology and
Behavior of an Endangered Species, pp. 29-31 ( Garden City, NY: Natural History Press
1970).
10 The wolves of Alaska, which have never been listed under the ESA, would constitute a
seventh population, with equally uncertain boundaries.
11 For example, should global warming proceed and arctic snow cover diminish, will the
genes for white coats diminish in the arctic wolves? That may be likely, since more brightly
colored wolves would be at a disadvantage in much of the year and over a growing area.
Natural selection would then tend to disfavor these animals and their offspring.
12 P.L. 93-205, § 3(11), 87 Stat. 886.

---

CRS-4
that definition was amended to include the term distinct population segment (DPS)
and was limited to vertebrate DPSs only.13 The change was controversial.
The General Accounting Office (GAO) (now the Government Accountability
Office) recommended limiting the definition of species to higher taxonomic
categories than populations, and exclude all distinct populations, including
geographically separated populations.14 GAO proposed the following definition: “The
term ‘species’ includes any subspecies of fish, wildlife, or plants.”15 GAO found the
1973 definition to be overly broad:
We found that Interior’s Fish and Wildlife Service is listing populations of
species in limited geographical areas as endangered or threatened instead of
listing the entire species. This has occurred because the Service has interpreted
the definition of “species” to include populations, regardless of their size,
location, or total numbers. Using the Service’s interpretation of the term,
squirrels in a specific city park could be listed as endangered even though there
is an abundance of squirrels in other parks in the same city and elsewhere. Such
listings had increased the number of potential conflicts between endangered and
threatened species and federal, state, and private projects and programs.16
Congress did not follow the GAO recommendation. It agreed with FWS that
the service needed to be able to adopt different management practices for different
populations, based on their need. A Senate committee report discussing populations
said “the committee agrees that there may be instances in which FWS should provide
for different levels of protection for populations of the same species,” although it
advised the practice be used “sparingly and only when the biological evidence
indicates that such action is warranted.”17
Thus, Congress revised and limited the definition of species in 1978 by
eliminating taxonomic categories below subspecies from the definition, except for
vertebrates.18 The revised, and still current, definition is: “any subspecies of fish or
wildlife or plants, and any distinct population segment of any species of vertebrate
13 P.L. 95-632; 16 U.S.C. § 1532(16).
14 GAO Testimony before the Subcommittee on Resource Protection, No. 108960, p. 5
(April 3, 1979).
15 GAO Testimony before the Subcommittee on Resource Protection, No. 108960, Attach.
1 (April 3, 1979).
16 GAO Testimony before the Subcommittee on Resource Protection, No. 108960, p. 3-4
(April 3, 1979).
17 S.Rept. 96-151, p. 7 (May 15, 1979). The discussion occurs after the amendment,
because, according to the Senate report, “some clarification would be useful.”
18 H.Rept. 95-1625 at 25 (September 25, 1978). Restriction to vertebrates is a severe
limitation, in terms of numbers of species able to enjoy this level of protection. Insects
alone outnumber all other animals — including vertebrates — by three to one. Donald J.
Borror, et al., An Introduction to the Study of Insects, p. 1. (Saunders College Publishing:
New York, 5th ed. 1981).

---

CRS-5
fish or wildlife which interbreeds when mature.”19 However, the phrase distinct
population segment had no meaning in the scientific community, outside of the ESA,
and was not used in endangered species listings for nearly two decades.
Regulatory History of Distinct Population Segments. A DPS generally
refers to a portion of a listed species, separated from the rest of the species by genetic
distinction and range. The legislative history offers two examples of when different
protection is appropriate within a species: 1) when a U.S. population of an animal is
near extinction even though another population outside the United States is more
abundant; and 2) where conclusive data have been available only for certain
populations of a species and not for the species as a whole.20
In 1996 a policy regarding DPS was introduced by FWS (hereinafter referred to
as “the Policy”).21 The Policy contains the criteria that must be met for protection
of a species at the population level. First, the population segment must be discrete.
Factors considered to determine discreteness are whether the segment is “markedly
separated from other populations of the same taxon as a consequence of physical,
physiological, ecological, or behavioral factors.”22 Discreteness can also be found
if the population is delimited by international governmental boundaries. Although
state boundaries are frequently used to describe a DPS, they cannot be used under the
Policy to determine discreteness.
Next, the population segment must be found to be significant, meaning its
demise would be an important loss of genetic diversity.23 Four factors are listed in
the policy for determining a species’ significance: 1) persistence of the segment in
an ecological setting unusual or unique for the taxon; 2) evidence that loss of the
DPS would result in a significant gap in the range of the taxon; 3) evidence that the
DPS represents the only surviving natural occurrence of a taxon within its historic
range; or 4) evidence that the DPS differs markedly from other populations of the
species in its genetic characteristics. Genetic evidence is allowed to be considered
but is not required. The policy indicates that “available scientific evidence of the
discrete population segment’s importance” will be considered in finding significance,
but does not specify the best available scientific evidence.
If a species is found to be both discrete and significant, then its status is
reviewed to see whether it is endangered or threatened. A DPS species is reviewed
to determine whether it should be listed under exactly the same procedures as any
other listing. The listing determination is to be based solely on the “best scientific
and commercial data available.”24
19 ESA § 3; 16 U.S.C. § 1532(16).
20 S.Rept. 96-151, p. 7 (May 15, 1979).
21 61 Fed. Reg. 4722 (February 7, 1996).
22 61 Fed. Reg. at 4725.
23 61 Fed. Reg. at 4724.
24 ESA § 4(b); 16 U.S.C. § 1533(b).

---

CRS-6
Pros and Cons of Distinct Population Segments. Agency efficiency
and focus were two intended benefits of DPSs, according to the Policy. The Policy
said determining DPSs will “concentrate ... efforts toward the conservation of
biological resources at risk of extinction.”25 The Policy suggested the practice of
using DPSs could help endangered species by focusing on smaller groups:
This may allow protection and recovery of declining organisms in a more timely
and less costly manner, and on a smaller scale than the more costly and extensive
efforts that might be needed to recover an entire species or subspecies. The
Services’ [FWS & the National Marine Fisheries Service’s] ability to address
local issues (without the need to list, recover, and consult rangewide) will result
in a more effective program.26
The FWS has followed Congress’s admonition to apply the practice “sparingly.”
According to FWS, only 39 of the 374 vertebrates listed under the ESA are DPSs.
Some have criticized DPSs as being used to remove ESA protections from
certain segments of a listed species. In three cases, the listing classification of DPSs
appears to be used solely to remove animals from protected status.27 The DPS
designation and the delisting occurred on the same day in the same Federal Register
notice. Those three cases are:
! Columbian white-tailed deer, Douglas Co. DPS — July 24, 2003;
! Gray wolf, Western Great Lakes DPS — February 8, 2007;
! Grizzly bear, Yellowstone DPS — March 29, 2007.
In other examples, the species has become downlisted (having its status dropped
from endangered to threatened) the same day as being designated a DPS:
! Gray wolf, Western DPS — downlisted April 1, 2003;
! Gray wolf, Eastern DPS — downlisted April 1, 2003.
However, for many more species, the designation of a DPS improved its
protection status. Here are some examples:
! California Bighorn Sheep, Sierra Nevada DPS — listed as
endangered January 3, 2000;
! Canada Lynx, contiguous U.S. DPS — listed as threatened
March 24, 2000;
! Atlantic Salmon, Gulf of Maine DPS — listed as endangered
November 17, 2000;
25 61 Fed. Reg. at 4725.
26 61 Fed. Reg. at 4725.
27 In the case of the bald eagle, a petition to recognize a new bald eagle DPS in Arizona was
filed at the time the entire bald eagle species was being removed from the ESA. The DPS
designation would have kept ESA protections in place for the Sonoran Desert bald eagle.
However, FWS found the Sonoran population did not meet the criteria for a DPS. 72 Fed.
Reg. 37345, 37357 (July 7, 2007).

---

CRS-7
! Dusky Gopher Frog, Mississippi DPS — listed as endangered
December 4, 2001;
! Pygmy Rabbit, Columbia Basin DPS — listed as endangered
March 5, 2003;
! California Tiger Salamander, Sonoma County DPS — listed as
endangered March 19, 2003;
! Northern Sea Otter, Southwest Alaska DPS — listed as threatened
August 9, 2005.
Gray Wolf Distinct Population Segments
Since the issuance of the Policy, FWS has pursued dividing the gray wolf into
more DPSs. The regulatory actions regarding gray wolf DPSs are numerous. In 2003
FWS divided wolves into three DPSs: Western, Eastern and Southwestern.28 This
rulemaking then downlisted the Eastern and Western DPSs from endangered to
threatened under the ESA. At the same time, gray wolves were removed from
protection in 14 southern and eastern states where they have not occurred in recent
times. This rulemaking was vacated by two federal courts, which is discussed later
in this report. After the 2003 DPS rulemaking was nullified, two other DPSs of the
gray wolf were proposed: Northern Rocky Mountain, and Western Great Lakes.29
The Western Great Lakes population was declared a distinct population segment in
2007, and delisted at the same time.30 On that same date, the Northern Rockies DPS
was designated and the population delisted, except for the population in Wyoming
because Wyoming’s state laws were found not to provide enough protection for the
wolf.31
Efforts to name the wolves of the Alexander Archipelago in Alaska as
threatened or endangered have not succeeded,32 in part because the wolves in that
region have not been considered as a DPS.
As noted above, wolf taxonomy is complex, but the choices made in
distinguishing DPSs have significant effects. In particular, if FWS agrees with
taxonomic lumpers, and recognizes only a few DPSs, then the recovery task
becomes simpler than it would be if many DPSs are recognized. Some observers
would argue that the very rare wolf sightings in Northern New York and New
28 68 Fed. Reg. 15803 (April 1, 2003). This rule was vacated by court order. See Defenders
of Wildlife v. U.S. Dept. of the Interior, 354 F. Supp. 2d 1156 (D. Or. 2005). A discussion
of that case is presented later in this report.
29 The Northern Rocky Mountain DPS includes Washington, Oregon, Utah, Montana,
Idaho, and Wyoming; the Western Great Lakes DPS includes North Dakota, South Dakota,
Minnesota, Wisconsin, and Michigan.
30 72 Fed. Reg. 6052 (February 8, 2007).
31 72 Fed. Reg. 6106 (February 8, 2007). FWS is considering delisting the population in
Wyoming, based on a 2007 state law. 72 Fed. Reg. 36969 (July 6, 2007).
32 See Biodiversity Legal Foundation v. Babbitt, 943 F. Supp. 23 (D.D.C. 1996) (remanding
the decision not to list the Alexander Archipelago gray wolf to DOI, as its decision was not
based solely on the best scientific and commercial data); 62 Fed. Reg. 46709 (September 4,
1997) (upon remand, no finding that the wolf was threatened).

---

CRS-8
England should represent a portion of a DPS which extends into Canada, and
therefore entitle them to recovery in their own right.33 In addition, whether a few
lone wolves inhabit the area or simply visit it occasionally, reintroduction proponents
would further argue that an abundance of apparently suitable habitat and high prey
populations make the region suitable for recovery efforts.
Regardless of the merits or demerits of this argument and the surrounding facts,
Northeast wolf designation hinges on a taxonomic assessment that the language of
the ESA elevates far beyond an academic debate between lumpers and splitters.
FWS considers the wolves (if any) in that area to be part of the same DPS of much
larger area.34 And if a portion of the DPS reaches its recovery goals, FWS — arguing
that it does not have legal responsibility to recover a species throughout its historic
range — would be relieved of the burden of recovering the species in the remainder
of the DPS’s range. Thus, the decision of whether to mount an effort to recover
relatively rare wolves in the remote Northeast (and certain other areas) depends on
two questions, one legal and one scientific:
! Does ESA require that a species be recovered in all or most of the
remaining areas of suitable habitat?
! Do (or did) the wolves of the Northeast constitute a DPS, and if
none remain, should presumably genetically similar wolves in
nearby parts of Canada be used to repopulate the area?
Two cases address these issues.
Litigation Regarding Western and Eastern DPSs. The rule downlisting
two of the three DPSs of the wolf in 2003 was challenged in two federal district
courts. The dispute focused on how a DPS’s range was defined under the ESA. The
plaintiff environmental groups before the District Court for the District of Oregon
argued that FWS considered only where the wolves were currently located when
determining their viability. This allowed FWS to count wolves only in the areas they
occupied. However, FWS had found areas outside of the wolves’ current range that
33 See 72 Fed. Reg. 6051-103 (February 8, 2007) for a discussion of wolf recovery goals,
including goals for establishing additional populations of the Western Great Lakes DPS.
34 Essentially, one DPS of the lower 48 states is created from all regions not in three named
areas. Thus, according to FWS, the lower 48 states has one population of wolves, except:
(1) Where listed as an experimental population;
(2) Minnesota, Wisconsin, Michigan, eastern North Dakota (that portion north
and east of the Missouri River upstream to Lake Sakakawea and east of the
centerline of Highway 83 from Lake Sakakawea to the Canadian border), eastern
South Dakota (that portion north and east of the Missouri River), northern Iowa,
northern Illinois, and northern Indiana (those portions of IA, IL, and IN north of
the centerline of Interstate Highway 80), and northwestern Ohio (that portion
north of the centerline of Interstate Highway 80 and west of the Maumee River
at Toledo); and
(3) Mexico.
See FWS website at [http:/ecos.fws.gov/tess_public/SpeciesReport.do].

---

CRS-9
were suitable habitat, although no wolves were present. The plaintiffs argued that this
method was contrary to the ESA and prior caselaw, because the act requires that a
species is endangered if it is at risk of extinction in “all or a significant portion of its
range.” The court agreed that FWS had violated the ESA by equating the wolves’
current range with a “significant portion of its range.”35 The court vacated the rule.
The other suit was before the District Court for the District of Vermont, which
issued a decision eight months after the Oregon court. The plaintiffs in Vermont
challenged the final rule’s designation of an Eastern DPS, a change from the
proposed rule. The proposed rule had two DPSs for that area: a Northeast DPS and
a Western Great Lakes DPS. The court found procedural flaws and also that the FWS
failed to consider the “significant portion of its range” in a way consistent with the
ESA.36 The court criticized FWS’s method before vacating the rule: “The FWS
simply cannot downlist or delist an area that it previously determined warrants an
endangered listing because it ‘lumps together’ a core population with a low to non-
existent population outside of the core area.”37

Experimental Populations
In 1982 Congress added the concept of experimental populations to the ESA as
a way of reintroducing species without severe restrictions on the use of private and
public land in the area.38 Experimental population designations are sometimes
referred to as Section 10(j) rules. The practice allows introduction of a species
outside its current range to restore it to its historic range.
Two criteria must be met for an experimental population to comply with the
law. First, DOI must have authorized the release of the population. Second, the
population must be wholly separate geographically from other animals of that
species.39 Congress required the separation so that the introduced population could
be clearly distinguished.
Members of an experimental population are considered to be threatened under
the act, and thus, can have special rules written for them.40 In fact, Congress referred
to special rules for experimental populations as a way to reduce public opposition to
35 Defenders of Wildlife v. U.S. Dept. of the Interior, 354 F. Supp. 2d 1156 (D. Ore. 2005).
36 National Wildlife Federation v. Norton, 386 F. Supp. 2d 553 (D. Vt. 2005). FWS has
since changed its interpretation of a “significant portion of its range.” See DOI Solicitor’s
Opinion, M-37013 (March 16, 2007), available at [http://www.doi.gov/solicitor/M37013.
pdf].
37 National Wildlife Federation v. Norton, 386 F. Supp. 2d at 556.
38 P.L. 97-304 §6(6), 96 Stat. 1424; 16 U.S.C. § 1539(j).
39 ESA § 10(j); 16 U.S.C. § 1539(j).
40 ESA § 10(j)(2)(C); 16 U.S.C. § 1539(j)(2)(C). See discussion of Section 4(d) Rules,
below.

---

CRS-10
the release of certain species, using the red wolf as an example.41 Congress suggested
in a report that the special regulations could allow killing members of the species:
The committee fully expects that there will be instances where the regulations
allow for the incidental take of experimental populations .... The committee also
expects that, where appropriate, the regulations could allow for the directed
taking of experimental populations. For example, the release of experimental
populations of predators, such as red wolves, could allow for the taking of these
animals if depredations occur or if the release of these populations will continue
to be frustrated by public opposition.42
Unlike DPSs, experimental populations may not necessarily have the same
protections under the ESA. FWS will first determine whether the experimental
population is of a species that is in imminent danger of extinction. That decision is
based on whether the loss of the population would appreciably diminish the species’
prospect for survival. If so, the experimental population is deemed essential and is
treated as an endangered species. Currently, there are no essential experimental
populations. If it is deemed nonessential, the experimental population is treated as
a species that is proposed for listing as threatened or endangered. There is no critical
habitat designation for an experimental population if it is nonessential. Also, federal
actions that may take a member of the population do not require a Section 7
consultation under the ESA, unless the species is in a national wildlife refuge or a
national park.
Examples of species with nonessential experimental populations are the
Colorado pikeminnow (or squawfish), the southern sea otter, the gray wolf in the
Southwest and in the Yellowstone area, the black-footed ferret, and the whooping
crane.
Experimental Populations of Gray Wolves
Despite near-eradication of wolves in the lower 48 states, some of the wolves’
old territories survived in their absence, though in a highly modified form. At the
end of the 20th century, FWS formed plans to reintroduce the wolf to parts of its
historic range, using the experimental population provisions of the ESA. No
reintroduction was more controversial than that in the greater Yellowstone
ecosystem, where all other large vertebrates were still present, and where many
scientists agreed that elk populations — a favorite wolf prey — had reached harmful
levels. When wolves were returned, the science community was nearly giddy
anticipating the potential effects from a first-ever return of a major predator to a
nearly intact ecosystem. The excitement was intense partly because the Yellowstone
area was already well studied, with long-term data on many species, including both
competitors (e.g., coyotes and, to some extent, grizzlies) and potential prey (e.g., elk,
moose, and bison). As scientists had expected, wolves had a profound effect on elk,
but there is also evidence of effects that were less predictable — on aspens,
41 1982 U.S. Code Cong. and Admin. News, p. 2807.
42 1982 U.S. Code Cong. and Admin. News, at 2834.

---

CRS-11
cottonwoods, beavers, beetles, mice, red foxes, ravens, and voles, among others.43
However, the road to the reintroduction was, and still is, fraught with litigation and
controversy.
Wolves also had been exterminated in the southwest. FWS recognized a
separate subspecies, the Mexican wolf (Canis lupus baileyi), which was probably
gone from the United States but found in very low numbers in Mexico. After a
cooperative and successful captive breeding program of wolves obtained from
Mexico, reintroduction was begun in 1998, in an area centered in the Apache
National Forest in Arizona and the Gila National Forest in New Mexico. In both the
Yellowstone and the Southwest cases, litigation was a major factor in the
reintroduction effort.
Yellowstone Litigation. While the recovery plan for the Northern Rockies
gray wolf acknowledged that the species may have to be reintroduced into the area
around Yellowstone National Park, that decision was controversial. Suit was filed to
compel FWS to bring some wolves to Yellowstone. However, the court ruled the
action was moot as it could not compel FWS to act,44 and an appropriations rider in
1992 blocked any funding for bringing the wolf to the area.
In 1995 and 1996 FWS released 66 gray wolves from Canada in Yellowstone
and central Idaho. A man accused of violating the ESA for killing one member of the
Yellowstone experimental population argued that he had killed a Canada wolf, which
was not an endangered species. This argument failed. The Ninth Circuit upheld the
regulations for the experimental population, holding that once the wolves from
Canada were introduced into the park, they became protected under the ESA.45
Another lawsuit argued that because the Yellowstone experimental population
may interact and breed with the few lone wolves in the area the experimental
population violated Section 10(j) of the ESA. (The lone wolves may have been
remaining wolves that somehow survived extermination, feral wolves, or wolves
dispersing from farther north.) Section 10(j) requires that experimental populations
must be “wholly separate geographically from nonexperimental populations of the
same species.” (ESA § 10(j)(1); 16 U.S.C. § 1539(j)(1).) The district court ruled that
the Yellowstone population would have to be removed. However, the Tenth Circuit
overruled the decision.46 The court rejected the argument that the legislative history
of experimental populations (as discussed earlier in this report) meant that the
experimental population must be separate from every naturally occurring individual
animal. The court deferred to the DOI management plan for the reintroduction,
finding it did not conflict with the statute.
43 For an account of some of the changes, and a sense of the excitement in the scientific
community, see Jim Robbins, “Lessons from the Wolf,” Scientific American (June 2004).
44 Defenders of Wildlife v. Lujan, 792 F. Supp. 834 (D.D.C. 1992) (referring to P.L. 102-
154, 105 Stat. 970, 993-94 (1991)).
45 United States v. McKittrick, 142 F.3d 1170 (9th Cir. 1998).
46 Wyoming Farm Bureau Federation v. Babbitt, 199 F.3d 1224 (10th Cir. 2000).

---

CRS-12
A more recent claim disputed FWS management of the wolves. A rancher
argued the agency failed to control wolves that were preying on livestock. After FWS
killed three wolves, including the lead male wolf of the offending pack, no more
depredations were found. The court dismissed the claims on procedural grounds.47
Southwest Litigation. The reintroduction of the wolf to the Southwest was
no less controversial. Ranchers sued, claiming the action violated the National
Environmental Policy Act (NEPA), as well as the ESA. The court found for FWS,
even though livestock owners and FWS had different estimates as to the impact of
the wolves on domesticated stock.48
Once the wolf was reintroduced to the Southwest, environmentalists sued FWS
for not acting to modify the reintroduction regulations.49 The action was dismissed
as moot. The area remains a center of intense public controversy about wolves.
Section 4(d) Rules
Special rules may be issued for both distinct population segments and
experimental populations. When a species is designated as threatened, rather than
endangered, FWS has discretion to issue special rules for that species. (Endangered
species have protections that are expressly stated in the act.) Under Section 4(d) of
the ESA, FWS may decide how the protections of the act related to taking, or
harming of the threatened species, are applied. These regulations are called Section
4(d) rules or special rules. A DPS is treated like a species under the act; therefore,
the special regulation provision also applies to threatened DPSs. Under Section
10(j)(3)(C), experimental populations are treated as threatened species, and so are
also covered under this provision. Special rules provide customized protection that
FWS deems necessary and advisable for the species’ conservation. FWS is not
limited in determining the protections and can allow the full range of protections in
the act to threatened species. The special rules are promulgated in Title 50 (Part 17)
of the Code of Federal Regulations.
Section 4(d) Rules for Gray Wolves. According to FWS, Section 4(d)
rules are intended to reduce conflicts between the provisions of the act and needs of
people near the areas occupied by the species. This type of special rule has been in
effect for the threatened gray wolves in Minnesota for many years, and was extended
to gray wolves in other states, when and where the wolf was downlisted. Under the
rule for Minnesota, individual wolves that have preyed on domestic animals can be
killed by designated government agents. FWS asserts that this rule avoids even
larger numbers of wolves being killed by private citizens who otherwise might take
wolf control into their own hands.50
47 Gordon v. Norton, 322 F.3d 1213 (10th Cir. 2003).
48 New Mexico Cattle Growers v. U.S. Fish and Wildlife Service, 1999 WL 34797509
(D.N.M. 1999).
49 Center for Biological Diversity v. Kempthorne, 498 F. Supp. 2d 293 (D.D.C. 2007).
50 50 C.F.R. § 17.40(d).

---

CRS-13
In 2003 as part of the rulemaking that was vacated, FWS issued Section 4(d)
rules for two DPSs: Eastern and Western. The special rules would have allowed
individuals to kill Western DPS wolves in the act of attacking livestock on private
land, and to harass wolves near livestock. Permits to kill wolves could also be issued
to landowners who showed wolves routinely were present and formed a significant
risk to livestock. FWS said that, as in Minnesota, the rule would “increase human
tolerance of wolves in order to enhance the survival and recovery of the wolf
population.”51 In Michigan and Wisconsin citizens would be able to kill any wolf
within one mile of killed livestock, and in other Eastern states beside Minnesota, any
lethal measures could be used within four miles of such a site. (68 Fed. Reg. at
15868.) This rule was vacated, as discussed earlier.
51 68 Fed. Reg. at 15864.

---