Defenders of Wildlife v. Ryan Zinke , 849 F.3d 1077 ( 2017 )


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  •  United States Court of Appeals
    FOR THE DISTRICT OF COLUMBIA CIRCUIT
    Argued September 23, 2016              Decided March 3, 2017
    No. 14-5300
    DEFENDERS OF WILDLIFE, ET AL.,
    APPELLEES
    v.
    RYAN ZINKE, IN HIS OFFICIAL CAPACITY AS SECRETARY OF
    THE UNITED STATES DEPARTMENT OF THE INTERIOR, ET AL.,
    APPELLANTS
    STATE OF WYOMING, ET AL.,
    APPELLEES
    Consolidated with 14-5311, 14-5312, 14-5313, 14-5314,
    14-5315
    Appeals from the United States District Court
    for the District of Columbia
    (No. 1:12-cv-01833)
    Joan M. Pepin, Attorney, U.S. Department of Justice,
    argued the cause for Federal Appellants. With her on the briefs
    were John C. Cruden, Assistant Attorney General, and David C.
    Shilton, Attorney.
    2
    Jay Jerde, Special Assistant Attorney General, Office of the
    Attorney General for the State of Wyoming, argued the cause
    for appellant State of Wyoming. Jeremiah I. Williamson,
    Assistant Attorney General, entered an appearance.
    John A. Sheehan was on the brief for amicus curiae
    Wyoming Wolf Coalition-2013's in support of appellant State of
    Wyoming.
    Timothy J. Preso argued the cause for appellees/cross-
    appellants Defenders of Wildlife, et al. With him on the brief
    was Ralph E. Henry, Jr.
    Anna M. Seidman, Douglas S. Burdin, Jeremy S. Clare,
    Michael T. Jean, and John I. Kittel were on the briefs for the
    non-governmental defendant-intervenor-appellants/cross-
    appellees. Christopher A. Conte entered an appearance.
    Before: ROGERS, BROWN and PILLARD, Circuit Judges.
    Opinion for the Court filed by Circuit Judge ROGERS.
    ROGERS, Circuit Judge: The gray wolf in Wyoming has
    been a protected species since 1973 pursuant to the Endangered
    Species Act (“ESA”) and its predecessor. In 2011, the Secretary
    of the Interior proposed to delist the wolf on the basis of the
    recovery of the Northern Rocky Mountain gray wolf population
    and the conservation management plan of the State of Wyoming.
    Environmental groups opposed the delisting, and thereafter
    Wyoming made statutory and regulatory changes and created an
    Addendum to its management plan. Upon consideration of these
    changes and other data, the Fish and Wildlife Service, acting on
    the Secretary’s behalf, delisted the wolf in Wyoming as it had in
    the adjacent states of Montana and Idaho. Removal of the Gray
    Wolf in Wyoming From the Federal List of Endangered and
    3
    Threatened Wildlife and Removal of the Wyoming Wolf
    Population’s Status as an Experimental Population, 
    77 Fed. Reg. 55,530
     (Sept. 10, 2012) (the “Rule”). Environmental
    groups sued, and the district court vacated the Rule, agreeing
    that the Service had arbitrarily determined that Wyoming had
    put into place adequate “regulatory mechanisms.” 
    16 U.S.C. § 1533
    (a)(1)(D). The court rejected the environmental groups’
    other challenges to the Rule.
    The Secretary and the State of Wyoming appeal, principally
    on the ground that the district court erred by failing to defer to
    the Service’s reasonable interpretation of “regulatory
    mechanisms” to include the State’s management plan for a wolf
    population buffer, which although not itself legally binding, is
    a practical entailment of the State’s statutory population minima.
    Environmental groups cross-appeal the district court’s
    conclusions that the Rule includes adequate provisions on
    genetic connectivity between wolf subpopulations and does not
    imperil the wolves in a “significant portion” of their range. For
    the following reasons, we reverse the judgment vacating the
    Rule and otherwise affirm.
    I.
    Section 4(a)(1) of the ESA provides that the Secretary is to
    determine whether a species is endangered or threatened because
    of one or more of the following factors:
    (A) the present or threatened destruction, modification,
    or curtailment of its habitat or range; (B)
    overutilization for commercial, recreational, scientific,
    or educational purposes; (C) disease or predation; (D)
    the inadequacy of existing regulatory mechanisms; or
    (E) other natural or manmade factors affecting its
    continued existence.
    4
    
    16 U.S.C. § 1533
    (a)(1). This determination is to be made
    “solely on the basis of the best scientific and commercial data
    available . . . after taking into account those efforts, if any, being
    made by any State . . . to protect such species, whether by
    predator control, protection of habitat and food supply, or other
    conservation practices, within any area under its jurisdiction.”
    
    Id.
     § 1533(b)(1)(A). A species — defined to include “any
    distinct population segment . . . which interbreeds when
    mature,” id. § 1532(16) — must be listed if its survival is
    threatened or endangered “throughout all or a significant portion
    of its range,” id. § 1532(6), (20). Section 4(f) requires the
    Secretary to develop and implement recovery plans for all listed
    species, id. § 1533(f)(1), incorporating “objective, measurable
    criteria which, when met, would result in a determination . . .
    that the species be removed from the list,” id.
    § 1533(f)(1)(B)(ii). Once the species has recovered sufficiently
    to be delisted, Section 4(g) requires the Secretary, in cooperation
    with the States, to monitor the species’ status “for not less than
    five years.” Id. § 1533(g)(1). Additionally, the Secretary is
    instructed to “make prompt use of the authority . . . to prevent a
    significant risk to the well being of any such recovered species.”
    Id. § 1533(g)(2). By regulation, the Secretary has instructed that
    upon listing a species the Fish and Wildlife Service (hereinafter,
    “the Service”) shall develop and implement recovery plans
    calling for “improvement in the status of listed species to the
    point at which listing is no longer appropriate under the criteria
    set out in section 4(a)(1) of the [ESA].” 
    50 C.F.R. § 402.02
    .
    The Northern Rocky Mountain gray wolf had by the 1930s
    been extirpated from Montana, Idaho, and Wyoming by western
    settlers who aggressively poisoned, trapped, and shot them. In
    the 1980s, gray wolves from Canada began to colonize
    northwestern Montana. In 1995 and 1996, 35 wolves from
    Alberta and British Columbia were reintroduced in Central
    Idaho, and 31 more were reintroduced in Yellowstone National
    5
    Park, virtually all of which is in northwestern Wyoming. The
    Service set recovery goals for Montana, Idaho, and Wyoming
    of at least 10 breeding pairs and 100 wolves, for a total Northern
    Rocky Mountain population of at least 30 breeding pairs and
    300 wolves, with adequate genetic connectivity between the
    three subpopulations (i.e., at least one migrant per generation
    that disperses from one subpopulation to another and
    successfully breeds). 
    76 Fed. Reg. 61,782
    , 61,791, 61,814 (Oct.
    5, 2011) (“NPRM”).
    The Service designated the Northern Rocky Mountain gray
    wolf as a distinct population segment in 2008, and proposed in
    2009 to delist the wolf in Montana and Idaho. Following
    various court challenges and intervention by Congress, that
    delisting occurred in 2011. Reissuance of Final Rule to Identify
    the Northern Rocky Mountain Population of Gray Wolf as a
    Distinct Population Segment and to Revise the List of
    Endangered and Threatened Wildlife, 
    76 Fed. Reg. 25,590
     (May
    5, 2011); see also All. for the Wild Rockies v. Salazar, 
    672 F.3d 1170
    , 1171–72 (9th Cir. 2012). In proposing delisting in
    Wyoming in 2011, the Service recounted the characteristics and
    history of the gray wolf. NPRM, 76 Fed. Reg. at 61,788–89.
    These characteristics include adaptability, resiliency,
    territoriality, an ability to reproduce quickly, and a tendency to
    live in family packs of two to twelve, although sometimes
    significantly larger. From 1995 to 2008, the Northern Rocky
    Mountain gray wolf population grew an average of 20%
    annually despite an average human-caused mortality rate of
    23%. By 2002, the recovery goal had been met for three
    consecutive years. At the end of 2011, the Northern Rocky
    Mountain gray wolf population consisted of a minimum of 1,774
    wolves and 109 breeding pairs, thus far exceeding the Service’s
    recovery goals. Rule, 77 Fed. Reg. at 55,539. This population
    represented a 400-mile “southern range extension of a vast
    contiguous wolf population that number[ed] over 12,000 wolves
    6
    in western Canada and about 65,000 wolves across all of Canada
    and Alaska.” Id. at 55,547.
    The Service’s proposal to delist the remaining Northern
    Rocky Mountain gray wolves in Wyoming was based on
    federal-state cooperative efforts to develop an adequate state
    regulatory framework, taking into account court decisions that
    had found prior state plans deficient. First, because a significant
    part of the Wyoming gray wolf subpopulation lives beyond
    Wyoming’s jurisdiction on tribal and federal lands — the Wind
    River Indian Reservation and Yellowstone National Park — the
    Service concluded that it would suffice for Wyoming to
    maintain a wolf population of “at least” 10 breeding pairs and
    100 wolves in the parts of the State over which Wyoming has
    jurisdiction. NPRM, 76 Fed. Reg. at 61,788. The wolves on
    tribal and federal lands, in turn, would provide an “additional
    buffer” above minimum recovery goals, id., thus roughly
    aligning Wyoming with the existing management requirements
    of 15/150 in Montana and Idaho, id. at 61,791. To meet these
    obligations, Wyoming agreed to repeal a regulatory requirement
    that it aggressively manage the wolf population down to the bare
    minimum required by law. In addition, it stated in its
    management plan that it intended “to maintain an adequate
    buffer above the minimum recovery goals” to ensure that
    unexpected mortality did not jeopardize its compliance with the
    10/100 minima. Id. at 61,788. Next, Wyoming would manage
    wolves as game animals in a permanent trophy area that
    comprises 15.2% of the State, in which the vast majority of
    Wyoming wolves live. During the peak dispersal season, the
    trophy area would also expand southward approximately 1,300
    square miles and cover an additional 1.3% of the State, to
    protect wolves migrating to and from the Idaho subpopulation.
    The remaining area, which covers only 19% of the State’s
    suitable wolf habitat, would be designated a predator area in
    which wolves could be killed with few restrictions.
    7
    Taking these commitments together, the Service concluded
    that Wyoming had provided for adequate regulatory
    mechanisms and proposed delisting contingent upon Wyoming
    enacting the agreed-upon changes into law. Id. at 61,811.
    Wyoming did so. See, e.g., 
    Wyo. Stat. Ann. § 23-1
    -
    101(a)(xii)(B)(I), (II); 
    id.
     § 23-1-304(a), (n). Consistent with the
    Service’s practice of submitting its rulemakings for independent
    peer review, four of five peer reviewers agreed that, under the
    proposed regulatory framework, Wyoming’s wolf population
    would continue to be viable after delisting. Rule, 77 Fed. Reg.
    at 55,538. Some commenters disputed the adequacy of
    Wyoming’s management plan and, in particular, the danger that
    human-caused mortality could reduce the wolf population below
    Wyoming’s required minimum. See id. at 55,555. In response,
    Wyoming submitted an Addendum to its management plan to
    affirm its commitment to maintain an adequate population
    buffer above minimum recovery levels, to “be determined
    through an adaptive management approach and [which] may
    fluctuate based on natural population dynamics and the effects
    of specific management actions.” Wyo. Game & Fish Comm’n,
    Addendum: Wyoming Gray Wolf Management Plan at 3–5
    (Mar. 22, 2012) (the “Addendum”). The Service relied on this
    Addendum in promulgating the Rule, stating, for instance, that
    “Wyoming’s wolf population will be further buffered because
    [the State Commission] intends to maintain an adequate buffer
    above minimum population objectives.” 77 Fed. Reg. at 55,538;
    id. at 55,555–56.
    The district court, in response to two lawsuits challenging
    the Rule, granted the environmental groups’ motion for
    summary judgment in part. It upheld Wyoming’s management
    plan as adequate to ensure genetic connectivity between the
    three gray wolf subpopulations. It also upheld the Service’s
    determination that the predator area in southern and eastern
    8
    Wyoming does not constitute a “significant portion” of the gray
    wolf’s range, and that a lack of protection in those areas will not
    prevent genetic exchange. It concluded, however, that
    Wyoming’s inadequate regulatory framework rendered arbitrary
    the Service’s determination that the wolf is not threatened or
    endangered in Wyoming. The district court found that, although
    the Rule imposed on Wyoming a duty to manage above the
    minimum level of 10 breeding pairs and 100 wolves, and
    although Wyoming statutes had been amended to require “at
    least” the minimums, only the Addendum to the State’s
    management plan included a commitment to managing above
    that level and it was not legally enforceable. Absent that legal
    commitment to maintain the buffer, the district court vacated the
    Rule. See Defs. of Wildlife v. Jewell, 
    68 F. Supp. 3d 193
    ,
    209–10 (D.D.C. 2014).
    The Secretary, Wyoming, Safari Club, and the National
    Rifle Association appeal the vacatur of the Rule, and the
    environmental groups (hereinafter, “appellees”) cross-appeal the
    denial of summary judgment on their genetic connectivity and
    “significant portion” challenges to the Rule. Our review of the
    grant or denial of summary judgment is de novo. See Defs. of
    Wildlife v. Jewell, 
    815 F.3d. 1
    , 7 (D.C. Cir. 2016). Where, as
    here, the district court reviewed agency action under the
    Administrative Procedure Act (“APA”), our review is highly
    deferential to the agency, see American Wildlands v.
    Kempthorne, 
    530 F.3d 991
    , 997–98 (D.C. Cir. 2008), while
    according no particular deference to the judgment of the district
    court, see In re Polar Bear Endangered Species Act Listing, 
    709 F.3d 1
    , 8 (D.C. Cir. 2013); accord Friends of Blackwater v.
    Salazar, 
    691 F.3d 428
    , 432 (D.C. Cir. 2012).
    9
    II.
    Under Section 4(a) of the ESA, one of the statutory factors
    that the Secretary must consider in determining whether to delist
    a protected species is “the inadequacy of existing regulatory
    mechanisms.” 
    16 U.S.C. § 1533
    (a)(1)(D). Section 4(b), in turn,
    requires the Secretary to consider a broad range of conservation
    efforts, if any, being made by the state to protect the species.
    See 
    id.
     § 1533(b)(1)(A). The Secretary contends that nothing in
    the ESA requires those efforts to be legally binding.
    Tracking the familiar two-step analysis under Chevron
    U.S.A., Inc. v. Natural Resources Defense Council, Inc., 
    467 U.S. 837
    , 842–43 (1984), the Secretary points out that the plain
    language of “regulatory mechanisms” is broader than only
    legally binding measures. Had Congress intended to so limit the
    analysis, it could have used “State law or regulation,” as it did
    elsewhere in the ESA, e.g., 
    16 U.S.C. § 1535
    (f). Moreover, a
    requirement that Section 4(b) efforts be legally binding would
    be duplicative of Section 4(a)(1)(D), which addresses existing
    “regulatory mechanisms.” 
    Id.
     § 1533(a)(1)(D). Therefore, the
    Secretary concluded the term “regulatory mechanisms” was
    ambiguous and may permissibly include state management plans
    that do not have the force of law. We agree that Congress has
    not “directly spoken” to the question, Chevron, 
    467 U.S. at 842
    ,
    and that the term is ambiguous, see 
    id. at 843
    , for the reasons the
    Secretary explains. Further, under Chevron’s second step, it was
    “permissible,” 
    id.,
     for the Secretary to rely on Wyoming’s
    management plan, which includes a commitment to manage for
    a buffer in conjunction with its statutory obligations. The
    Secretary properly does not view the management plan as
    merely a speculative promise of future action in light of
    Wyoming’s statutory and regulatory amendments. Although
    appellees rely on the dictionary in maintaining that a
    “‘regulation’ demands more than voluntary compliance,” see
    10
    Appellees Br. 32 (citing 13 OXFORD ENGLISH DICTIONARY 524
    (2d ed. 1989)), they overlook that Wyoming “is implicitly
    ‘required’ [to maintain a buffer] as the only practicable means
    of achieving the explicit requirement of maintaining at least” 10
    breeding pairs and 100 wolves on state land. Fed. Appellants
    Reply Br. 13 (first emphasis added); 
    Wyo. Stat. Ann. § 23-1
    -
    304(a).
    Much of the parties’ underlying legal dispute about the
    adequacy of Wyoming’s management plan has been addressed
    by this court. In In re Polar Bear, 
    709 F.3d 1
    , this court
    discussed “regulatory mechanisms” and “conservation efforts”
    interchangeably, concluding that the Service reasonably found
    that existing regulatory mechanisms were inadequate despite
    Canada’s use of sport-hunting fees to fund local conservation
    programs, which it determined did nothing to offset the threat to
    polar bears from loss of sea ice habitat. 
    Id.
     at 16–17. More
    significantly, and post-dating the district court’s vacatur of the
    Rule, this court upheld the Service’s determination to rely on a
    state management plan in Defenders of Wildlife, 815 F.3d at 6,
    17, crucial terms of which were conservation agreements
    voluntarily entered into by landowners seeking to earn
    environmental mitigation credits that would relieve them of
    additional duties if the species at issue were listed. As here, the
    exercise of judgment by the Service in that case was based upon
    its experience under similar management plans in two adjacent
    states, with species-protective terms that, although not
    themselves legally codified, the Service had seen in operation
    and was reasonably certain would be fulfilled. Id. at 6–7. There
    too, environmental objections were raised similar to those of
    appellees, but the court concluded the Service adequately
    responded to them and exercised its judgment in a responsible
    and reasoned way. Id. at 17.
    In other words, the question now before the court turns on
    11
    whether the rulemaking record demonstrates the Service
    exercised its judgment in a reasonable way in concluding that
    Wyoming’s management plan, which explains how the State
    intends to carry out its day-to-day implementation of its legal
    obligations, will adequately protect Wyoming’s gray wolf
    population after delisting. See 
    16 U.S.C. § 1533
    (a)(1)(D),
    (b)(1)(A). That determination, this court acknowledged, is a
    quintessential judgment call that Congress left to the Secretary,
    and by delegation to the Service, which has years of experience
    in evaluating what is reasonably likely to be implemented and
    effective. See Defs. of Wildlife, 815 F.3d at 17. The ESA
    provides no definition of “regulatory mechanisms,” and neither
    the district court nor appellees suggests why the Secretary’s
    interpretation is unreasonable. Although appellees may disagree
    with the Service’s conclusion that Wyoming can be trusted to
    manage for a buffer, that is a separate question. Given
    Congress’s direction that state conservation efforts must be
    considered, 
    16 U.S.C. § 1533
    (b)(1)(A), their consideration as
    part of the State’s “regulatory mechanisms” is hardly contrary
    to congressional intent. Appellees disagree with the Service’s
    assessment of Wyoming’s management plan, but not with the
    statutory obligation to take into account all state conservation
    efforts, or with the proposition that, in some instances, non-
    binding measures “if sufficiently certain and effective to
    alleviate a threat [of endangerment] may render a [legally
    binding] regulatory mechanism unnecessary . . . after delisting,”
    Appellees Br. 37-38. The Rule may be set aside only if
    “arbitrary, capricious, an abuse of discretion, or otherwise not in
    accordance with law.” Am. Wildlands, 
    530 F.3d at 997
     (quoting
    
    5 U.S.C. § 706
    (2)); see Motor Vehicle Mfrs. Ass’n of U.S., Inc.
    v. State Farm Mut. Auto. Ins. Co., 
    463 U.S. 29
    , 42–43 (1983).
    The record demonstrates that the Service reasonably and
    adequately responded to concerns about the reliability of
    Wyoming’s management plan. As the preamble to the Rule
    12
    makes clear, the Service determined that Wyoming’s
    management plan is a reliable indicator of how the State plans
    to implement its statutes and regulations because that plan
    aligned with the State’s own incentives. That is, managing at
    minimum levels “would severely limit State flexibility to
    address wolf depredation issues, limit wolf harvest
    opportunities, and increase the risk of relisting.” Rule, 77 Fed
    Reg. at 55,567. The Service similarly noted that a failure to
    ensure a buffer would place Wyoming at risk of violating its
    own statutory and regulatory commitments, if faced with
    unexpected and uncontrollable sources of mortality like disease.
    
    Id.
     As a point of comparison, the Service also looked to the
    post-delisting behavior of the adjacent states of Montana and
    Idaho, which had both maintained wolf populations well above
    minimum targets. See 
    id. at 55
    ,567–68. It noted that none of
    the states had indicated any interest in managing down to
    minimum levels; the Service underscored that state wildlife
    managers “have consistently reiterated . . . their desire not to
    come close to their floor levels” due to concerns about reduced
    management flexibility and potential relisting. 
    Id. at 55,567
    .
    The district court did not question those assumptions or
    considerations, but vacated the Rule solely because the
    provision in Wyoming’s management plan for an additional
    buffer is not legally binding. Nothing in the ESA demands that
    level of certainty, however, and in Defenders of Wildlife, the
    court upheld the withdrawal of a listing proposal where the
    Service had found that the voluntary conservation efforts were
    “sufficiently certain to be implemented” based on the strength
    of the participating state’s incentives, 815 F.3d at 6 (quoting the
    Service’s Policy for Evaluation of Conservation Efforts When
    Making Listing Decisions, 
    68 Fed. Reg. 15,100
    , 15,114–15
    (Mar. 28, 2003)). The Service’s decision to delist in the absence
    of legal certainty is compatible with the ESA’s requirement for
    monitoring of the species after delisting “for at least five years”
    13
    and its emergency provisions authorizing the Secretary to take
    immediate action to ensure the delisted species does not become
    threatened or endangered again. See 
    16 U.S.C. § 1533
    (b)(7),
    (g). So understood, the Service could reasonably conclude that
    Wyoming’s efforts set forth in its management plan were
    sufficiently certain to be implemented based on the strength of
    the State’s incentives. And although Wyoming’s antagonistic
    history toward wolves may provide appellees reason to disagree,
    the Service took that history into account, see, e.g., Rule, 77
    Fed. Reg. at 55,566, and it worked with the State to rectify
    deficiencies previously identified by the courts, id. at 55,551–52.
    That appellees disagree with the Service does not undercut its
    reasoned determination that, in light of Wyoming’s plan to
    manage for a buffer, especially given the State’s own interests,
    Wyoming has established an adequate regulatory framework.
    Appellees nonetheless maintain the Service’s reliance on a
    non-binding management plan is arbitrary because the Service
    had already determined that the threat of human mortality must
    be “adequately regulated.” Appellees Br. 38–39 (quoting Rule,
    77 Fed. Reg. at 55,588). The preamble to the Rule does not state
    that Wyoming’s buffer must be regulated; to the contrary, it was
    the general threat of human-caused mortality that required
    regulation “in the form of binding minimum population targets
    by geographic area.” 77 Fed. Reg. at 55,568. The Service found
    that such protections are in place. Wyoming is bound under its
    own law to manage for “at least ten (10) breeding pairs of gray
    wolves and a total of at least one hundred (100) individual gray
    wolves.” 
    Wyo. Stat. Ann. § 23-1-304
    (a). It will also use a
    licensing system to regulate the frequency with which wolves
    can be killed in the trophy area, see, e.g., Wyo. Admin. Code
    Game Hunt Ch. 21 § 7, which affords Wyoming additional
    control over human-caused mortality. See Greater Yellowstone
    Coal., Inc. v. Servheen, 
    665 F.3d 1015
    , 1032 n.7 (9th Cir. 2011).
    Elsewhere, the preamble is even clearer on this point, discussing
    14
    regulation and buffers separately: “[I]f human-caused mortality
    is adequately regulated and population targets are sufficient to
    allow for other potential unforeseen or uncontrollable sources of
    mortality, no other potential threats are likely to compromise the
    population’s viability.” Rule, 77 Fed. Reg. at 55,588. Because
    the Service never deemed a regulatory buffer necessary, it did
    not contradict itself by failing to require one.
    Nor did the Service disclaim any reliance on the states’
    incentives to manage for a buffer, as appellees suggest. The
    preamble to the Rule states:
    Should management needs be identified in future years,
    all three States have regulatory authority to modify
    management to meet such needs; although we did not
    rely upon this in making our decision, we recognized
    all three States have a strong incentive to maintain the
    [Northern Rocky Mountain distinct population
    segment] and its subpopulations well above minimum
    population levels.
    77 Fed. Reg. at 55,590 (emphasis added). Appellees read “this”
    to refer to the states’ “strong incentive” in the following clause,
    while the Secretary responds that it refers to the states’
    “regulatory authority” in the preceding clause. Even assuming
    the sentence is not a model of clarity, its meaning is apparent
    upon examination. If “this” were meant to refer to “strong
    incentive” in the following clause, then there would be no
    conceptual link between the two halves of the sentence, and they
    would have been separated by a period rather than a semi-colon.
    The sentence, moreover, comes at the end of a section
    explaining the adequacy of Wyoming’s current regulatory
    structure, and cannot fairly be understood as meaning “And even
    if the current regulatory structure is inadequate, Wyoming can
    just change it.” Instead, the Service noted Wyoming’s authority
    15
    to legislate while making clear that it did not rely on this fact; it
    relied on the State’s incentives to make sure future legislation is
    unnecessary. The preamble, further, makes clear that the
    Service did rely on state incentives, see, e.g., Rule, 77 Fed. Reg.
    at 55,567, so it would have been illogical for it to claim
    otherwise.
    Also without merit is Wyoming’s position that it is not
    required to manage for a buffer at all. This sleight of hand may
    lend some credence to appellees’ concerns about the State’s
    commitment, but it cannot overcome the rulemaking record and
    the documents submitted by the State in order to obtain
    delisting. The Service considered “unacceptable” Wyoming’s
    previous approach of managing down to bare minimum levels.
    Rule, 77 Fed. Reg. at 55,588. More to the point, the preamble
    states that Wyoming “will, and must, maintain a buffer to
    consistently meet its minimum management targets.” Id. at
    55,556 (emphasis added). This language manifests a clear intent
    by the Service to bind Wyoming, and therefore the preamble
    itself has the force of law. See Kennecott Utah Copper Corp. v.
    U.S. Dep’t of Interior, 
    88 F.3d 1191
    , 1223 (D.C. Cir. 1996).
    Wyoming’s Addendum acknowledges that managing for
    minimum populations would restrict its ability to deal with
    depredating wolves and risk a status review and potential
    relisting. See Rule, 77 Fed. Reg. at 55,567; 
    16 U.S.C. § 1533
    (b)(7), (g). As the Secretary explains, Wyoming is
    implicitly required to maintain a buffer “as the only practicable
    means of achieving the explicit requirement” of maintaining at
    least 10 breeding pairs and 100 wolves on state land. Fed.
    Appellants Reply Br. 13; 
    Wyo. Stat. Ann. § 23-1-304
    (a).
    Appellees’ remaining challenges to Wyoming’s regulatory
    framework, which the district court did not reach in light of its
    vacatur of the Rule, also lack merit. First, the Service was not
    arbitrary in relying on Wyoming’s management plan to maintain
    16
    the statutorily required buffer, contrary to appellees’ contention
    that maintaining a buffer would conflict with state law.
    Appellees point to Wyoming’s lethal take statute but ignore the
    statutory and regulatory limitations that preserve the State’s
    buffer authority. The statute provides for the promulgation of
    rules under which permits “shall be issued as long as the
    removals authorized by such permits could not reduce the
    numbers of gray wolves below” the 10/100 minimum. 
    Wyo. Stat. Ann. § 23-1-304
    (n). The rules “shall provide for
    suspending the issuance of permits or cancelling existing
    permits if further lethal control could cause the numbers of gray
    wolves to be reduced below” the minimum. 
    Id.
     As
    promulgated, those rules provide that a “Lethal Take Permit
    shall only be issued by the Department if legal removal of gray
    wolves will not prevent the Department from” meeting the
    10/100 minimum. Wyo. Admin. Code Game Hunt Ch. 21 §
    7(a). If further lethal take “may prevent the Department from
    achieving [its] management objectives,” the issuance of
    additional permits “shall be immediately suspended” and
    existing permits “shall be immediately cancelled.” Id.
    § 7(b)(iii). In addition to these binding provisions, the
    Addendum states that “[i]f the population approaches the
    minimum recovery level . . . the Department has the statutory
    authority to suspend issuance of Lethal Take Permits or cancel
    existing Lethal Take Permits.” Addendum at 7.
    The Service concluded that these provisions will not
    interfere with Wyoming’s ability to maintain a buffer because
    they require the suspension or cancellation of permits if further
    mortality “could” compromise the State’s minimums. Rule, 77
    Fed. Reg. at 55,557. If State law had said “would” or “will,”
    then it might conflict with a buffer, but State law requires
    suspension of permits upon the possibility of compromise. See
    id. Appellees focus on the phrase “permits shall be issued,”
    maintaining this mandatory language trumps any discretion the
    17
    State might otherwise have to provide for a buffer. They ignore
    that the mandate (“shall”) is tempered by a condition (“as long
    as [issuance] could not reduce” the population below 10/100).
    
    Wyo. Stat. Ann. § 23-1-304
    (n) (emphasis added). In other
    words, the mere possibility that minimums “could” be
    compromised is enough to warrant the permit’s rejection. See
    77 Fed. Reg. at 55,557. To the extent appellees also maintain
    that, because the preamble’s reference to “could” is not present
    in the State regulation, a permit must be issued as long as it “will
    not prevent” Wyoming from reaching its minimum, Appellees
    Br. 47–48 (quoting Wyo. Admin. Code Game Hunt Ch. 21
    § 7(a)), they overlook that the permit “shall only be issued . . .
    if [it] will not prevent” Wyoming from reaching its minimum.
    Wyo. Admin. Code Game Hunt Ch. 21 § 7(a). The regulation
    sets a necessary condition, not a mandate, for the permit to be
    issued. See also id. § 7(b) (“If the requirements of . . . Section
    7(a) are met . . . .”). As noted, a separate provision requires the
    suspension or cancellation of permits if they “may” prevent
    Wyoming from managing for 10/100, see id. § 7(b)(iii), thus
    preserving the State’s ability to maintain a buffer if the wolf
    population falls to near minimum levels.
    Appellees also point out that Wyoming’s lethal take statute
    authorizes a permit when wolves are “harassing . . . livestock or
    other domesticated animals,” 
    Wyo. Stat. Ann. § 23-1-304
    (n),
    and yet it fails to define “harassing.” They worry that if the
    State were to define “harassing” broadly, permitting under that
    provision could jeopardize any planned buffer. In downplaying
    this concern, the Service relied on a letter from Wyoming’s
    Governor stating that prior to issuing a permit due to
    harassment, State officials will verify that wolves were present
    and that an actual attack was likely. Rule, 77 Fed. Reg. at
    55,585–86 (citing Letter of Gov. Matthew H. Mead to U.S. Fish
    & Wildlife Serv. (May 15, 2012)). Appellees maintain that the
    Service’s reliance on the Governor’s letter was unreasonable,
    18
    because it is a non-binding promise, but that issue is largely
    irrelevant. Regardless of how broadly Wyoming defines
    “harassing,” or whether it independently verifies harassment
    before issuing a permit, it is legally bound to suspend all
    harassment permits if they “could” compromise the State’s
    minimums. 
    Wyo. Stat. Ann. § 23-1-304
    (n).
    Second, appellees maintain the Service’s delisting action
    was arbitrary because it failed to secure a regulatory
    commitment to suspend permits where necessary to ensure
    genetic connectivity between subpopulations. They correctly
    point out that the Service had identified this as a “Major Issue”
    in a mark-up of Wyoming’s proposed regulations,
    recommending that Wyoming add genetic connectivity as
    another grounds for suspending permits. Appellees, however,
    tell only half of the story. The Service also noted in the mark-up
    that it “could live with a commitment to this goal generally here,
    and let the [management] plan include more specifics.” Draft
    Revisions, Chapter 21 Regulations – Gray Wolf Management,
    at 4 (Feb. 24, 2012). Consistent with that guidance, the final
    State regulation added a general commitment to “ensur[ing]
    genetic diversity and connectivity,” even though it was not
    included in Section 4(a)(i) as the Service’s reviewer would have
    preferred. See Wyo. Admin. Code Game Hunt Ch. 21 § 4(a)(ii).
    To the extent appellees maintain the Service arbitrarily
    ignored that Wyoming’s lethal take regulations could override
    that non-binding commitment to genetic connectivity, the
    Service correctly points out that the ESA “does not mandate that
    regulatory mechanisms exist to protect a species from any
    conceivable impact.” Fed. Appellants Reply Br. 31. Rather, the
    ESA requires protection only “against threats that would cause
    the species to be ‘an endangered species or a threatened
    species.’” Id. (quoting 
    16 U.S.C. § 1533
    (a)(1)). Because the
    rulemaking record showed that the wolves’ genetic health is
    19
    strong, and because Wyoming has other tools at its disposal
    (including reduction in harvest levels and in its own wolf control
    actions, and, if necessary, translocating wolves to other
    subpopulations), the Service concluded that the State’s
    commitment to ensuring genetic connectivity into the Greater
    Yellowstone Area (“GYA”) was sufficient. Rule, 77 Fed. Reg
    at 55,595–96. Even if a close issue, because the Service
    considered this permitting exception important, the studies in the
    record support the Service’s view that genetic connectivity is not
    an immediately pressing concern. See Michael D. Jimenez et
    al., Wolf Dispersal in the Northern Rocky Mountains in Western
    United States: 1993 – 2008 (2011) (“Jimenez Study”); Bridgett
    M. vonHoldt et al., A Novel Assessment of Population Structure
    and Gene Flow in Grey Wolf Populations of the Northern Rocky
    Mountains of the United States, 19 Molecular Ecology 2214
    (2010) (“vonHoldt Study”). The Service determined that “even
    if no new genes entered into the GYA (a near impossibility),
    genetic diversity is likely many decades, and perhaps a century
    or more, away from becoming an issue and even then, it would
    be unlikely to threaten the GYA population.” Rule, 77 Fed.
    Reg. at 55,596. In this context, the Service’s acceptance of a
    non-binding commitment to genetic connectivity was not
    arbitrary and capricious.
    Third, appellees maintain that any buffer will be
    undermined by Wyoming’s allowance for unlimited killing of
    wolves “doing damage to private property.” 
    Wyo. Stat. Ann. § 23-3-115
    . Although the Service relied on the State’s ability to
    limit human-caused mortality, e.g., Rule, 77 Fed. Reg. at 55,555,
    appellees view this provision to create a “hole . . . in the State’s
    authority.” Appellees Br. 54. In particular, appellees are
    concerned about the ability of ranchers to bait wolves onto their
    property by leaving animal carcasses out. The Service
    concluded this concern was “improbable [and] theoretical,”
    noting that a representative of the Wyoming Attorney General’s
    20
    office advised that baiting could be prosecuted under Wyoming
    law. Rule, 77 Fed. Reg. at 55,561. In the Service’s judgment,
    “such a scenario is unlikely to occur and exceedingly unlikely
    to become a meaningful source of mortality” because ranchers
    are more likely to seek a lethal take permit or hunting tag than
    risk prosecution for baiting. Id. It noted as well that, baiting
    aside, similar defense-of-property allowances have been in place
    in Montana and Idaho since delisting and the overall wolf
    population has continued to grow. Id. at 55,585. Indeed, the
    record reflects that in Idaho only six defense-of-property kills
    are known to have occurred in 2009 and thirteen in 2010. Thus,
    the Service determined that the allowance “will not compromise
    . . . Wyoming’s ability to meet the agreed-upon population
    objectives.” Id. Appellees speculate that baiting could become
    most problematic as population levels decrease to near 10/100,
    at which point permits would be suspended and ranchers would
    have no choice but to bait. Again, as the Secretary observes, the
    ESA does not require a regulation to address every “far-fetched
    ‘what-if’ scenario” that opponents of delisting can imagine.
    Fed. Appellants Reply Br. 35. Given the slight impact of these
    allowances in Idaho and Montana, and the absence of evidence
    of baiting, the Service was not unreasonable in rejecting this
    concern.
    III.
    On cross appeal, appellees contend that the Service
    arbitrarily concluded that genetic connectivity is currently
    sufficient, and will remain so after delisting. They also contend
    the Service arbitrarily concluded Wyoming’s unregulated
    predator area is not a “significant portion” of the wolves’ range.
    We are not persuaded that the district court erred in rejecting
    appellees’ challenges.
    21
    A.
    To ensure the wolves’ long-term genetic health, the Service
    has determined that, as a general rule, there should be at least
    one effective migrant per generation, i.e., one wolf that travels
    every four years from another subpopulation and passes on its
    genes. Rule, 77 Fed. Reg. at 55,593. The GYA is the most
    isolated core recovery area within the Northern Rocky Mountain
    region, and thus a key concern of the Service has been the
    number of effective migrants entering the GYA from northwest
    Montana and central Idaho.
    The Service relied on two studies to determine that genetic
    connectivity is currently sufficient. The Jimenez Study found
    that five radio-collared wolves had migrated into the GYA
    between 1992 and 2008, of which two were confirmed to have
    mated successfully and one was confirmed not to have. Rule, 77
    Fed. Reg. at 55,593. Because only 20–30% of wolves were
    radio-collared, the Service determined that the number of actual
    migrants was likely several times higher than the five
    documented. Applying the Jimenez Study’s estimate that 35%
    of migrants effectively breed, the Service concluded that there
    was likely more than one effective migrant per generation, and
    specifically as many as 1.5. Because the number of dispersals
    increase as the wolf population increases, and the Northern
    Rocky Mountain population increased from 55 to more than
    1,655 over the course of the study, the Service inferred that a
    large proportion of dispersals occurred in recent years.
    The vonHoldt Study sampled genetic material of Northern
    Rocky Mountain wolves between 1995 and 2004, when the total
    population was between 101 and 846 wolves. Id. It “detected
    genetically effective dispersal among the three recovery areas,”
    with high levels of genetic variation and low levels of
    inbreeding. vonHoldt Study at 4412. As the population
    expanded over the course of the study, “observed heterozygosity
    22
    remained high,” id. at 4416, and “[i]nbreeding coefficients . . .
    remained low for all recovery phases,” id. at 4417. A co-author
    of the vonHoldt Study, Daniel Stahler, determined separately
    that the genetic sampling data indicated a minimum of 0.42
    effective migrants per generation had entered the GYA during
    the study. There was consensus that this significantly
    underestimated the number of actual effective migrants because
    only about 30% of the population was sampled, but
    disagreement about how to calculate the actual number. One
    paper suggested that the Stahler estimate is “almost certainly
    low by at least half,” Rule, 77 Fed. Reg. at 55,593 (quoting
    Mark Hebblewhite et al., Restoration of Genetic Connectivity
    Among Northern Rockies Wolf Populations, 19 Molecular
    Ecology 4383, 4384 (2010) (“Hebblewhite et al., Genetic
    Connectivity”)), but Stahler has objected to that particular
    extrapolation as mere guesswork. The Rule’s preamble quoted
    Hebblewhite’s multiplier as a “suggest[ion],” while noting that
    additional analysis “may be needed” to pin down the actual
    number. Id.
    Appellees contend that these studies show that the
    minimum requirement of one effective migrant per generation
    has not been met, and that the Service’s contrary conclusion was
    arbitrary. They claim the Jimenez Study found “[o]nly two
    dispersing wolves actually bred,” Appellees Br. 61, thus
    resulting in approximately 0.62 effective migrants per
    generation. Leaving aside that this Study accounted for only
    20–30% of the wolf population, appellees ignore that two other
    dispersing wolves may have effectively bred, as only one of the
    five was confirmed not to have done so. Thus, it is possible that
    the dispersals observed by the Jimenez Study alone met the
    threshold, even before extrapolating the effective dispersals of
    the entire population. Appellees similarly take issue with the
    Service’s reliance on the vonHoldt Study because even
    assuming Hebblewhite is correct that the 0.42 effective migrant
    23
    rate is too low by half, a 0.84 rate would still be insufficient.
    They understand Stahler to believe that Hebblewhite
    overestimated the actual effective migrant rate. In fact, Stahler
    clarified that he was not claiming that the actual number could
    not be “as high as this (or higher in recent years),” but simply
    that no data supported quantifying the actual number as at least
    double the observed number. Email from Dan Stahler to Mike
    Jimenez and Seth Willey (Sept. 7, 2011). Contrary to appellees’
    assertion, the Service did not “fail[] to grapple with Stahler’s
    objection,” Appellees Reply Br. 10, but rather cited Stahler in
    noting that additional analysis may be needed. Rule, 77 Fed.
    Reg. at 55,593.
    The ESA requires that the Service rely on the “best
    scientific . . . data available,” 
    16 U.S.C. § 1533
    (b)(1)(A), and the
    Service’s evaluation of this data falls within its area of expertise
    and is entitled to deference by the court. Defs. of Wildlife, 815
    F.3d at 14. Appellees do not suggest that there are better studies
    available, nor do they meaningfully dispute that both studies’
    results are understated, requiring some extrapolation upward.
    Instead, they disagree with the Service’s conclusion that the
    studies show an effective migrant rate above one per generation.
    Such competing views about scientific data and policy choices,
    however, fail to show that the Service’s conclusions were
    arbitrary and capricious or contrary to law. In re Polar Bear,
    709 F.3d at 3.
    Of course, whether these levels of genetic connectivity will
    be sustained after delisting may be a closer question, but such a
    projection is still within the expertise of the Service. Two
    Service scientists noted that, because effective dispersals are
    hovering just above one-per-generation, “there is not a lot of
    wiggle room per assuring effective migration through natural
    dispersal into the GYA.” Ed Bangs and Mike Jimenez, Draft
    Memo at 3 (May 24, 2011) (“Bangs Memo”). The Service
    24
    nonetheless concluded that “the GYA wolf population will not
    be threatened by lower genetic diversity in the foreseeable
    future.” Rule, 77 Fed. Reg. at 55,596. It projected that the
    overall Northern Rocky Mountain wolf population will stabilize
    around 1,000 wolves after delisting in Wyoming. Id. at 55,594.
    Although appellees object that the projection has no basis,
    especially in light of the states’ documented hostility toward
    wolves and their binding commitments only to manage 400
    total, in reality, two years after delisting, known 2011
    populations remained many times larger than the minimums in
    Idaho (746), Montana (653), and the Northern Rocky Mountains
    as a whole (1,774). Rule, 77 Fed. Reg. at 55,539. These
    population numbers in adjacent states, which offer an indication
    of what Wyoming will experience after delisting, provided a
    rational basis for the Service to project that the Northern Rocky
    Mountain population will level off around 1,000 wolves.
    Appellees still maintain that even if the Service’s projection
    is accepted, it was arbitrary to conclude that effective dispersals
    will reach one per generation because of the increase in wolf
    killings and the paucity of effective dispersals when the
    population was under 1,000. As noted, currently known levels
    of effective dispersal provide very little cushion above the one-
    per-generation threshold, so “very small changes in survival of
    a very small proportion of dispersing wolves into Wyoming may
    have significant repercussions.” Bangs Memo at 2. The
    Secretary explains that the 1,300 square-mile flex area, which
    sits across the border from two protected areas in Idaho, was
    created to provide a protected corridor for dispersing wolves as
    they seek a southern route around the Teton Mountains. The
    Secretary also discounts the importance of the expansive
    predator area, because it contains little suitable habitat and sits
    to the southeast of the GYA subpopulation, while the Montana
    and Idaho subpopulations are to the northwest. And the
    Secretary allows for the possibility that some dispersing wolves
    25
    will wander into the predator area en route to the GYA, but
    concludes “it is certainly not the only or even the likeliest
    route.” Fed. Appellants Reply Br. 52; see 77 Fed. Reg. at
    55,564.
    Appellees object that the seasonal flex area is too small to
    protect migrants, citing a recommendation by Bangs and
    Jimenez that the permanent trophy area extend south to Big
    Piney, WY. As to length, the flex area is only protected for 4.5
    months per year, while an average dispersal takes 5.5 months to
    complete, thus ensuring that “the average dispersing wolf [will
    pass through] a free-fire zone for at least part of its journey.”
    Appellees Br. 70–71. And even in the protected flex area,
    appellees point out, dispersing wolves can still be killed by those
    holding lethal take or hunting permits. Appellees also refer to
    the Service’s conclusion in 2009 that, due to snow depths and
    concentration of prey, wolves dispersing into the GYA from the
    west were likely to skirt the mountains and “move through the
    predatory area.” See Final Rule to Identify the Northern Rocky
    Mountain Population of Gray Wolf as a Distinct Population
    Segment and To Revise the List of Endangered and Threatened
    Wildlife, 
    74 Fed. Reg. 15,123
    , 15,176 (Apr. 2, 2009) (“2009
    Rule”).
    This aspect of appellees’ challenge too involves some
    sleight of hand. The predatory area proposed in 2009 was much
    larger (at least 88% of the State) than the current proposal. See
    
    id.
     The Service had recommended that Wyoming “minimize
    take in all suitable habitat and across all of Wyoming’s potential
    migration routes,” 
    id.,
     which the current permanent and flex
    trophy areas are aimed to accomplish. Rule, 77 Fed. Reg. at
    55,564. Moreover, the Service does not dispute that migrants
    will enter the predator area, but explains why that would not
    preclude dispersals: migrants are harder to locate and kill than
    resident wolves, as demonstrated by Idaho hunting data showing
    26
    minimal harvest in areas with few resident wolves even during
    peak dispersal season. See id.
    Were genetic connectivity entirely dependent on natural
    dispersals, it is possible Wyoming’s current management plan
    would prove inadequate due to the apparent closeness to the
    minimum threshold in the GYA. But the Service persuasively
    responded, pointing out that Wyoming has committed to account
    for dispersing wolves when setting quotas, and to collect
    samples to monitor for genetic diversity; further, if monitoring
    shows that natural dispersals are inadequate, it will modify its
    population management program; and if those modifications
    prove inadequate over numerous generations, it will employ
    human-assisted genetic exchange as a stopgap measure. Rule,
    77 Fed. Reg. at 55,595–96. In this way the Rule accounts for,
    and protects against, the possibility that natural dispersals could
    fall short, or at least it was not arbitrary and capricious for the
    Service to so conclude.
    Appellees lastly contend that the ESA’s purpose precludes
    the Service from delisting a species where its survival depends
    on human-assisted translocation (essentially, trapping a wolf and
    trucking it to another subpopulation to breed). This proves too
    much. The ESA aims “to provide a program for the
    conservation of” endangered and threatened species, 
    16 U.S.C. § 1531
    (b), by using “all methods and procedures which are
    necessary” to bring those species back to the point where the
    law’s protections are no longer necessary, 
    id.
     § 1532(3). From
    this purpose, appellees infer a prohibition against delisting if the
    ESA’s “methods and procedures” — i.e., “live trapping[] and
    transplantation,” id. — are still necessary. Yet if the Service
    cannot delist a species when live trapping and transplantation
    may still be necessary, the logic of appellees’ interpretation
    would mean delisting could not occur if other less invasive
    methods like “research, census, law enforcement, [and] habitat
    27
    acquisition” are still necessary. See id. By the same token, the
    Secretary’s regulations contemplate delisting even if the species
    depends on continued regulatory protection, see 
    50 C.F.R. § 424.11
    (d), so appellees’ view of the statutory imperative as
    allowing only an entirely self-sufficient species to be delisted
    can hardly be correct. The authority cited by appellees, Trout
    Unlimited v. Lohn, 
    559 F.3d 946
     (9th Cir. 2009), is not to the
    contrary. There, the Ninth Circuit concluded that the ESA
    requires consideration of the entire species, not just the naturally
    hatched portion, and that, in deciding to downlist the species, the
    Service rationally considered how the artificially hatched fish
    benefit naturally hatched fish. See 
    id.
     at 957–58. Thus,
    downlisting was appropriate even though that decision rested on
    the use of “artificial propagation,” one of the ESA’s “methods
    and procedures.” See 
    16 U.S.C. § 1532
    (3).
    Notably, the Secretary emphasizes that under the Rule
    translocation would only be necessary as a last resort, and that
    “‘natural connectivity is the preferred approach.’” Fed.
    Appellants Reply Br. 54 (quoting 77 Fed. Reg. at 55,565). The
    Service expects natural levels of dispersal to be sufficient, so
    “wolves in the GYA are not expected to need or rely on human-
    assisted migration often, if ever.” Rule, 77 Fed. Reg. at 55,565.
    This is not a case, then, in which greater reliance on such
    techniques could render a delisting decision arbitrary. It suffices
    to conclude that the ESA did not prohibit the Service from
    delisting in Wyoming where translocation could eventually be
    necessary as a stopgap measure after many generations of
    insufficient natural connectivity.
    B.
    Section 3 of the ESA defines an endangered species as one
    in danger of extinction “throughout all or a significant portion
    of its range.” 
    16 U.S.C. § 1532
    (6). In Wyoming’s predator area
    wolves can be killed without restriction, and appellees contend
    28
    it was arbitrary for the Service to conclude this is not a
    significant portion of the wolves’ range.
    The predator area contains only 19% of the State’s suitable
    habitat, and as of 2011, it contained only 3 of 27 breeding pairs,
    8 of 48 packs, and 46 of 328 wolves in Wyoming. Rule, 77 Fed.
    Reg. at 55,602. The Service concluded that even if all of those
    wolves were killed, the remaining wolves in Wyoming would be
    sufficient to maintain a recovered population. Id. As for
    dispersing wolves, it acknowledged that some will be killed in
    the predator area, but it concluded that even if no dispersing
    wolves successfully traversed the Wyoming predator area,
    genetic health would not be affected to the point of endangering
    the remainder, id. at 55,602–03, due in part to “the current high
    level of genetic diversity” in the Northern Rocky Mountain gray
    wolf population, id. at 55,596. Thus, according to the Service,
    the predator zone cannot be deemed a “significant portion” of
    the wolves’ range because the species would not become
    endangered even if every single wolf there were killed. Id. at
    55,602–03.
    Appellees respond that the Service “cannot have it both
    ways, deeming the predator zone insignificant even if all wolves
    in the area are killed, but then discounting the genetic-exchange
    impacts . . . by speculating that some wolves may survive” their
    passage through the predator zone. Appellees Reply Br. 28. But
    the Service has not offered “contradictory statements,” see id.,
    only complementary ones: it expects that some wolves will
    successfully traverse the predator area, but even if that proves
    incorrect, genetic health will not decline so much as to endanger
    the wolves. Rule, 77 Fed. Reg. at 55,602–03. Appellees’
    challenge rests on the mistaken assumption that migrants have
    no choice but to traverse the predatory area, making “safe
    passage through this area . . . essential to genetic exchange.”
    Appellees Br. 78. The rulemaking record is clear, however, that
    29
    wolves can disperse directly into the GYA from Idaho and
    Montana “without moving through Wyoming” at all, thereby
    accomplishing the desired connectivity goal. Rule, 77 Fed. Reg.
    at 55,564; see also id. at 55,534, 55,540.
    Appellees also maintain that the Service irrationally
    reversed its 2009 determination that all of Wyoming constituted
    a significant portion of the wolves’ range. See 2009 Rule, 74
    Fed. Reg. at 15,183. This 2009 determination was deemed
    arbitrary and capricious in 2010, see Wyoming v. U.S. Dep’t of
    the Interior, Nos. 09-CV-118J & 09-CV-138J, 
    2010 WL 4814950
    , at *45 (D. Wyo. Nov. 18, 2010), when based on a
    broader, more inclusive definition of “significant portion,”
    pursuant to a 2007 opinion of the Solicitor of the Interior that
    was later withdrawn. See Fed. Appellants Reply Br. 57. By
    contrast, the 2012 Rule is based on the Service’s new, more
    restrictive interpretation of the ambiguous phrase “significant
    portion” as a portion of the range that would endanger the
    species’ survival if removed. See Rule, 77 Fed. Reg. at
    55,601–02. Appellees do not challenge the Service’s definition
    of “significant portion;” rather, they maintain that even under
    that definition the predator area is significant and that the
    Service fails to explain the reversal of its 2009 determination.
    In 2010, the district court ruled that all of Wyoming was not
    appropriately subjected to trophy game management, without
    specifying how much of Wyoming could be so designated. In
    appellees’ view, then, the factual underpinnings of the 2009
    determination are unaffected by the district court’s ruling, and
    yet the Service has failed to explain why they are no longer
    controlling.
    The 2009 determination has been overtaken by events. Not
    only has the Service adopted a new definition of “significant
    portion of its range,” see Rule, 77 Fed. Reg. at 55,602–03, but
    Wyoming’s regulatory framework has changed, id. at
    30
    55,589–90, and new scientific data has become available in
    recent studies, see id. at 55,593 (citing the vonHoldt Study and
    the Jimenez Study). Indeed, Hebblewhite has concluded that
    vonHoldt’s 2010 study is more comprehensive and robust than
    her earlier work showing a lack of genetic connectivity:
    “[C]oncerns that this highly vagile and fecund species might
    suffer negative effects of genetic isolation . . . have been
    effectively laid to rest by vonHoldt et al.’s (2010) exhaustive
    work.” Hebblewhite et al., Genetic Connectivity at 4384. The
    Service has offered ample rationale for determining that the
    predator area was never “envisioned to meaningfully contribute
    to wolf recovery in the region” and is thus not a “significant
    portion of its range.” Rule, 77 Fed. Reg. at 55,602–03.
    Accordingly, we reverse the judgment vacating the Rule
    and otherwise affirm. The court has no occasion to consider the
    additional contentions of the Safari Club and NRA that the Rule
    reasonably advances conservation efforts and social tolerance
    for wolves among hunters and ranchers.