Humane Society of the United States v. Ryan Zinke (Lead) ( 2017 )


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  •  United States Court of Appeals
    FOR THE DISTRICT OF COLUMBIA CIRCUIT
    Argued October 18, 2016                Decided August 1, 2017
    No. 15-5041
    HUMANE SOCIETY OF THE UNITED STATES, ET AL.,
    APPELLEES
    v.
    RYAN ZINKE, SECRETARY OF THE INTERIOR, ET AL.,
    APPELLEES
    U.S. SPORTSMEN’S ALLIANCE FOUNDATION, ET AL.,
    APPELLANTS
    STATE OF WISCONSIN, ET AL.,
    APPELLEES
    Consolidated with 15-5043, 15-5060, 15-5061
    Appeals from the United States District Court
    for the District of Columbia
    (No. 1:13-cv-00186)
    Joan M. Pepin, Attorney, U.S. Department of Justice,
    argued the cause for federal appellants Zinke, et al. With her
    on the briefs were John C. Cruden, Assistant Attorney General
    at the time the brief was filed, and David C. Shilton, Attorney.
    2
    Nathan Gambill, Assistant Attorney General, Office of the
    Attorney General for the State of Michigan, argued the cause
    for appellants State of Michigan, et al. With him on the briefs
    were Bill Schuette, Attorney General, Aaron D. Lindstrom,
    Solicitor General, and Pamela J. Stevenson, Assistant Attorney
    General.
    James H. Lister argued the cause for appellant-defendant-
    intervenors Hunter Conservation Coalition, et al. With him on
    the briefs were Anna M. Seidman, Douglas S. Burdin, John I.
    Kittel, and Michael T. Jean. Jeremy E. Clare and William P.
    Horn entered appearances.
    Brad Schimel, Attorney General, Office of the Attorney
    General of the State of Wisconsin, Ryan J. Walsh, Chief
    Deputy Solicitor General, Daniel P. Lennington, Deputy
    Solicitor General at the time the briefs were filed, Jennifer L.
    Vandermeuse, Assistant Attorney General, and Thomas J.
    Dawson, Assistant Attorney General at the time the brief was
    filed, were on the brief for State of Wisconsin and Wisconsin
    Department of Natural Resources.
    Kathryn Landrum, Assistant Attorney General, Office of
    the Attorney General for the State of Minnesota, was on the
    brief for amicus curiae the State of Minnesota in support of
    appellants.
    Peter K. Michael, Attorney General, Office of the
    Attorney General for the State of Wyoming, James Kaste and
    D. David DeWald, Assistant Attorneys General, and Michael
    J. McGrady, Assistant Attorney General at the time the brief
    was filed, Joseph A. Foster, Attorney General, Office of the
    Attorney General for the State of New Hampshire, Douglas A.
    Bahr, Solicitor General, Office of the Attorney General for the
    State of North Dakota at the time the brief was filed, Sean D.
    3
    Reyes, Attorney General, Office of the Attorney General for the
    State of Utah, Cynthia Coffman, Attorney General, Office of
    the Attorney General for the State of Colorado, Lawrence G.
    Wasden, Attorney General, Office of the Attorney General for
    the State of Idaho, Derek Schmidt, Attorney General, Office of
    the Attorney General for the State of Kansas, and Timothy C.
    Fox, Attorney General, Office of the Attorney General for the
    State of Montana, were on the brief for amici curiae the States
    of Wyoming, et al. in support of defendants-appellants and
    intervenor-defendants-appellants.
    Ralph E. Henry argued the cause for appellees The
    Humane Society of the United States, et al. With him on the
    brief was Elizabeth Runyan Geise.
    Amy R. Atwood and Collette L. Adkins were on the brief
    for amicus curiae Center for Biological Diversity in support of
    plaintiffs-appellees The Humane Society of the United States.
    Before: GRIFFITH, MILLETT, and PILLARD, Circuit Judges.
    Opinion for the Court filed by Circuit Judge MILLETT.
    MILLETT, Circuit Judge: The gray wolf once roamed in
    large numbers across the contiguous forty-eight States. But by
    the 1960s, hunting, depredation, and habitat loss drove the gray
    wolf to the brink of extinction, and the federal government
    declared the gray wolf an endangered species. After a portion
    of the gray wolf population rebounded, the government
    promulgated the rule at issue here, which removes from federal
    protection a sub-population of gray wolves inhabiting all or
    portions of nine states in the Western Great Lakes region of the
    United States. The Humane Society of the United States
    challenges that rule as a violation of the Endangered Species
    Act of 1973 (“Act”), 16 U.S.C. § 1531 et seq., and the
    4
    Administrative Procedure Act (“APA”), 5 U.S.C. § 551 et seq.
    Because the government failed to reasonably analyze or
    consider two significant aspects of the rule—the impacts of
    partial delisting and of historical range loss on the already-
    listed species—we affirm the judgment of the district court
    vacating the 2011 Rule.
    I
    A
    Congress enacted the Endangered Species Act “to halt and
    reverse the trend toward species extinction,” and to do so
    “whatever the cost.” Tennessee Valley Auth. v. Hill, 
    437 U.S. 153
    , 184 (1978). As relevant here, a species is “endangered”
    if it “is in danger of extinction throughout all or a significant
    portion of its range[.]” 16 U.S.C. § 1532(6). A species is
    “threatened” if it “is likely to become an endangered species
    within the foreseeable future throughout all or a significant
    portion of its range.” 
    Id. § 1532(20).
    The Endangered Species Act directs the Secretary of the
    Interior to apply five factors in determining whether a
    “species” is endangered or threatened: (i) “the present or
    threatened destruction, modification, or curtailment of [the
    species’] habitat or range”; (ii) “overutilization [of the species]
    for commercial, recreational, scientific, or educational
    purposes”; (iii) “disease or predation”; (iv) “the inadequacy of
    existing regulatory mechanisms”; and (v) “other natural or
    manmade factors affecting [the species’] continued
    existence.”     16 U.S.C. § 1533(a)(1).          In making that
    determination, the Secretary must rely on “the best scientific
    and commercial data available[.]” 
    Id. § 1533(b)(1)(A).
    The
    Secretary of the Interior has delegated the authority to
    determine whether a species is “endangered” or “threatened”
    5
    to the Fish and Wildlife Service (“Service”).            50 C.F.R.
    § 402.01(b).
    The “species” that the Endangered Species Act protects
    are defined to include “any subspecies of fish or wildlife or
    plants, and,” of most relevance here, “any distinct population
    segment of any species of vertebrate fish or wildlife which
    interbreeds when mature.” 16 U.S.C. § 1532(16). 1 The Act
    does not define “distinct population segment.” Nor do agency
    regulations. The Service, however, has issued policy guidance
    stating that the existence of a “distinct population segment”
    turns upon the discreteness and significance of a sub-
    population as compared to the larger species population.
    Policy Regarding the Recognition of Distinct Vertebrate
    Population Segments Under the Endangered Species Act, 61
    Fed. Reg. 4,722, 4,725 (Feb. 7, 1996) (“Segment Policy”). The
    Segment Policy emphasizes that the Service’s authority to
    recognize distinct population segments should be “exercised
    sparingly.” 
    Id. at 4,724.
    To qualify as “discrete” under the Segment Policy, a
    domestic animal population must be “markedly separated from
    other populations of the same taxon as a consequence of
    physical, physiological, ecological, or behavioral factors[.]”
    Segment Policy, 61 Fed. Reg. at 4,725. The “significance” of
    a potential segment turns on such factors as: (i) the
    “[p]ersistence of the discrete population segment in an
    ecological setting unusual or unique for the taxon”; (ii)
    “[e]vidence that loss of the discrete population segment would
    result in a significant gap in the range of a taxon”; (iii)
    1
    The Endangered Species Act defines “species” in a way that
    differs from the scientific definition of species. As used in this
    opinion, “species” refers to the Act’s definition. The phrase
    “taxonomic species” or “taxon” refers to the scientific definition of
    a species.
    6
    “[e]vidence that the discrete population segment represents the
    only surviving natural occurrence of a taxon that may be more
    abundant elsewhere as an introduced population outside its
    historic range”; or (iv) “[e]vidence that the discrete population
    segment differs markedly from other populations of the species
    in its genetic characteristics.” 
    Id. Another key
    term in analyzing a species’ need for
    protection—“range”—is also left undefined by the Act. In
    2014, the Service adopted a policy statement defining “range”
    as a species’ “‘current range,’ not [its] ‘historical range.’”
    Final Policy on Interpretation of the Phrase “Significant
    Portion of its Range” in the Endangered Species Act’s
    Definitions of “Endangered Species” and “Threatened
    Species,” 79 Fed. Reg. 37,578, 37,583 (July 1, 2014) (“Range
    Policy”). The Range Policy further explains that a portion of a
    species’ range will be considered “significant” if the species
    would be in danger of extinction or likely to become so in the
    foreseeable future without that portion of its range. 
    Id. at 37,581.
    Once the Service determines that a species is endangered
    or threatened, it must add the species to a list of protected
    species in the Federal Register. 16 U.S.C. § 1533(c)(1). A
    listed species receives robust federal protections, including
    prohibitions on possessing, killing, selling, importing, or
    exporting its members. 
    Id. § 1538(a).
    Any person that
    knowingly violates those prohibitions faces criminal sanctions,
    including fines of up to $50,000 or a year of imprisonment. 
    Id. § 1540(b)(1).
    The Act further requires the Service “from time to time
    [to] revise” its lists of endangered and threatened species “to
    reflect recent determinations, designations, and revisions.” 16
    U.S.C. § 1533(c)(1). Every five years, the Service must
    7
    “review * * * and determine * * * whether any such species
    should * * * (i) be removed from such list; (ii) be changed in
    status from an endangered species to a threatened species; or
    (iii) be changed in status from a threatened species to an
    endangered species.” 
    Id. § 1533(c)(2)(A),
    (B).
    B
    1
    Regional subspecies of the taxonomic species “gray wolf”
    (Canis lupis) were declared endangered by the federal
    government between 1966 and 1976. The timber wolf (Canis
    lupus lycaon) was first designated as endangered and afforded
    protection in 1967, 32 Fed. Reg. 4,001, 4,001 (March 11,
    1967), followed by the Northern Rocky Mountain wolf (Canis
    lupus irremotus) in 1973, 38 Fed. Reg. 14,678, 14,678 (June 4,
    1973). Both the Mexican wolf (Canis lupus baileyi) and the
    Texas wolf (Canis lupus monstrabilis) were added to the list in
    1976. 41 Fed. Reg. 17,736, 17,737 (April 28, 1976); 41 Fed.
    Reg. 24,062, 24,066 (June 14, 1976).
    With the wolves’ numbers rebounding in certain areas, the
    federal government in 1978 reclassified the gray wolf from its
    regional listings into a single species listing divided into two
    groups: Minnesota gray wolves, which the Service determined
    had recovered to the point of only being threatened, and the
    gray wolf in the remaining forty-seven States, which remained
    endangered. See Reclassification of the Gray Wolf in the
    United States and Mexico, with Determination of Critical
    Habitat in Michigan and Minnesota, 43 Fed. Reg. 9,607, 9,608,
    9612 (March 9, 1978) (“1978 Rule”). 2
    2
    Those two groups were listed before the Endangered Species
    Act was amended to add “distinct population segments” to the
    8
    In 2003, the Service subdivided the gray wolf listing into
    three “distinct population segments”: an Eastern segment, a
    Western segment, and a Southwestern segment. Final Rule to
    Reclassify and Remove the Gray Wolf From the List of
    Endangered and Threatened Wildlife in Portions of the
    Conterminous United States; Establishment of Two Special
    Regulations for Threatened Gray Wolves, 68 Fed. Reg. 15,804,
    15,818 (April 1, 2003) (“2003 Rule”). Included in the Eastern
    segment were the Minnesota gray wolf population and any gray
    wolf population that existed in the Northeast region of the
    United States. 
    Id. at 15,859.
    The Service then designated the
    wolves in the Eastern and Western segments as threatened
    rather than endangered. 
    Id. at 15,857–15,858,
    15,862. The
    wolves within the Southwestern segment continued to be listed
    as endangered. 
    Id. Two district
    courts struck down the 2003 Rule’s attempted
    designation of those three distinct population segments. First,
    a district court in Oregon ruled that, by downlisting the species
    based solely on the viability of a small population within that
    segment, the Service was effectively ignoring the species’
    status in its full range, as the Endangered Species Act requires.
    See Defenders of Wildlife v. Secretary, U.S. Dep’t of the
    Interior, 
    354 F. Supp. 2d 1156
    , 1168–1169 (D. Or. 2005). The
    2003 Rule thus had the “effect of rendering the phrase
    [significant portion of its range] superfluous.” 
    Id. at 1168
    definition of “species.” See Endangered Species Act Amendments
    of 1978, Pub. L. No. 95-632, 92 Stat. 3,751, 3,752. Prior to the 1978
    amendments, the Act defined “species” to “include[] 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.” Endangered Species Act of 1973 § 3, Pub.
    L. 93-205, 87 Stat. 884, 886.
    9
    (alteration in original; internal quotation marks and citation
    omitted).
    Second, a district court in Vermont concluded that the
    Service impermissibly designated and downlisted the Eastern
    segment of gray wolves. National Wildlife Fed’n v. Norton,
    
    386 F. Supp. 2d 553
    , 564–565 (D. Vt. 2005). Fatal to the
    Service’s determination, the court concluded, was the Service’s
    decision to “lump” into the Eastern segment any gray wolves
    in the Northeast region of the United States, without
    ascertaining whether a gray wolf population even existed in the
    Northeast. See 
    id. In so
    holding, the court rejected the
    Service’s argument that the Endangered Species Act required
    it to include any Northeast region wolves in the segment to
    avoid turning them into an impermissible “non-DPS remnant”
    of gray wolves that neither fell within a recognized segment
    nor had independent species or subspecies status of its own. 
    Id. at 564–565.
    In the district court’s view, the Service instead
    could have continued the remnant’s endangered-species status.
    See 
    id. at 565.
    2
    The government did not appeal either the Oregon or the
    Vermont decision. Instead, in what turned out to be the first
    round in successive attempts to delist the gray wolves in the
    Western Great Lakes area, the Service promulgated a new rule
    in 2007 that created a “Western Great Lakes gray wolf distinct
    population segment” and simultaneously delisted that segment,
    removing it completely from the Endangered Species Act’s
    protections. See Final Rule Designating the Western Great
    Lakes Populations of Gray Wolves as a Distinct Population
    Segment; Removing the Western Great Lakes Distinct
    Population Segment of the Gray Wolf From the List of
    Endangered and Threatened Wildlife, 72 Fed. Reg. 6,052,
    10
    6,052 (Feb. 8, 2007) (“2007 Rule”). That rule soon met the
    same fate as its two predecessors. A district court in this circuit
    vacated it for “fail[ing] to acknowledge and address crucial
    statutory ambiguities” concerning the creation of distinct
    population segments for the purpose of delisting. Humane
    Society of the U.S. v. Kempthorne, 
    579 F. Supp. 2d 7
    , 9 (D.D.C.
    2008); 
    id. at 15.
    Again, the government did not appeal.
    In December 2008, the Solicitor of the Department of the
    Interior issued a memorandum analyzing the statutory
    authority for designating distinct population segments for the
    specific purpose of delisting them. See U.S. Fish and Wildlife
    Service Authority under Section 4(c)(1) of the Endangered
    Species Act to Revise Lists of Endangered Species and
    Threatened Species to “Reflect Recent Determinations,” Office
    of the Solicitor, U.S. Dep’t of Interior (Dec. 12, 2008)
    (“Solicitor’s Opinion”). The Solicitor concluded that the Act
    unambiguously allows the Service to identify a segment and
    then delist it. 
    Id. at 3–5.
    The Solicitor started by noting that, once the Service lists
    a species as threatened or endangered, it is obligated to
    periodically revise its list of endangered or threatened species
    in light of any changes in the conservation status of a species.
    Solicitor’s Opinion 3 (citing 16 U.S.C. § 1533(a), (c)(1)). The
    Solicitor then reasoned that the Endangered Species Act
    imposes no textual limit on the Service’s authority to revise its
    list of endangered or threatened species based on intervening
    information and determinations. 
    Id. at 4.
    On that basis, the
    Solicitor determined that the Act unambiguously permits the
    Service to designate a segment within a listed species,
    determine that the segment is no longer endangered or
    threatened, and delist it. 
    Id. at 3–5.
                                   11
    The Solicitor further opined that, even were the statutory
    text ambiguous, his interpretation was a reasonable
    construction of the statute and its purposes. Solicitor’s Opinion
    5–6. The Solicitor reasoned that, because subspecies and
    segments are parts of taxonomic species, any listing of a
    taxonomic species necessarily includes a listing of its
    constituent segments or subspecies. 
    Id. at 7.
    On that basis, the
    Solicitor concluded that, even if the Service could only delist
    an already-listed segment, that requirement would be satisfied
    by the listing of the species that encompassed the segment. 
    Id. The Solicitor
    also reasoned that delisting a recovered segment
    is consistent with the express statutory policies of the Act,
    including fostering federal-state cooperation and focusing
    resources where they are most needed. 
    Id. at 13–19.
    3
    Based on the Solicitor’s Opinion, the Service in 2009
    republished the 2007 rule without notice and comment, adding
    a discussion of “Issues on Remand.” Final Rule To Identify
    the Western Great Lakes Populations of Gray Wolves as a
    Distinct Population Segment and to Revise the List of
    Endangered and Threatened Wildlife, 74 Fed. Reg. 15,070,
    15,075 (April 2, 2009) (“2009 Rule”). The Service relied on
    the Solicitor’s determination that the Endangered Species Act
    permits the Service to “remove an already-listed entity from the
    appropriate list in its entirety, or to reduce the geographic or
    taxonomic scope of a listing to exclude a group of organisms
    previously included as part of an already-listed entity.” 
    Id. at 15,083
    (quoting Solicitor’s Opinion 5 n.8).
    Round Two of the Service’s attempt to delist the gray
    wolves in the Western Great Lakes area ended in the same
    manner as Round One: the 2009 Rule was challenged and
    vacated after the Service acknowledged that it had
    12
    impermissibly promulgated the rule without notice and
    comment, and agreed to settle the case. Humane Society of the
    U.S. v. Salazar, No. 09–1092, Docket Entry No. 27 (D.D.C.
    July 2, 2009).
    As a consequence of all those regulatory missteps, the
    status of gray wolves remained in 2009 what it had been in
    1978: Gray wolves in Minnesota were listed as “threatened,”
    while the wolves in the forty-seven other contiguous States
    were listed as “endangered.”
    C
    1
    This case is Round Three in the Service’s effort to divide
    and delist gray wolves in the broader Western Great Lakes
    region. In 2011, the Service issued a final rule that, in reliance
    on the Solicitor’s Opinion, purported to “revise the boundaries
    of the Minnesota” gray wolf population to include the wolves
    in all or portions of eight other states. Revising the Listing of
    the Gray Wolf (Canis lupus) in the Western Great Lakes, 76
    Fed. Reg. 81,666, 81,666, 81,670 (Dec. 28, 2011) (“2011
    Rule”). Specifically, the 2011 Rule designated the gray wolf
    population in Minnesota, Wisconsin, and Michigan, as well as
    portions of North Dakota, South Dakota, Iowa, Illinois,
    Indiana, and Ohio, as the Western Great Lakes Distinct
    Population Segment. 
    Id. at 81,666,
    81,670. In its next breath,
    the Service delisted that segment. 
    Id. at 81,723.
    In doing so, the Service again expressly adopted the legal
    analysis in the Solicitor’s Opinion regarding its authority to
    delist a segment. See 2011 Rule, 76 Fed. Reg. at 81,670,
    81,683. The Service then reasoned that, because more than 400
    miles existed between the gray wolf population in the Western
    13
    Great Lakes region and other gray wolf packs, the population
    qualified as “discrete.” 
    Id. at 81,671.
    The Service further
    found that the loss of the Western Great Lakes population of
    gray wolves, which contained “70 percent of North American
    gray wolves known to occur south of Canada,” would
    constitute a “significant gap in the range” of the “gray wolves
    in the United States[.]” 
    Id. at 81,672.
    The Service thus
    concluded that the population qualified as “significant.” 
    Id. Accordingly, the
    Service determined that the Western Great
    Lakes population of gray wolves constituted a “distinct
    population segment.” 
    Id. The Service
    next considered whether the segment was
    endangered or threatened throughout all or a significant portion
    of its range. 2011 Rule, 76 Fed. Reg. at 81,721–81,723. In
    making that determination, the Service explained that it would
    interpret “range” to mean “current range.” 
    Id. at 81,722.
    The
    Service also clarified that it would consider a portion of a
    species’ range to be “significant” if that portion is “important
    to the conservation of the species because it contributes
    meaningfully to the representation, resiliency, or redundancy
    of the species.” 
    Id. Finally, the
    Service concluded, after analyzing the five
    statutory endangerment factors, that the Western Great Lakes
    segment was neither endangered nor threatened throughout all
    or a significant portion of its range. 2011 Rule, 76 Fed. Reg.
    at 81,721–81,723. The Service explained that existing rates of
    mortality from disease and human causes had been insufficient
    to prevent growth of the population, and that state plans
    provided adequate monitoring of and protection for the wolf
    segment. See, e.g., 
    id. at 81,694;
    id. at 81,700.
    
                                   14
    2
    The Humane Society filed suit alleging that the 2011 Rule
    violated both the Endangered Species Act and the APA. The
    district court agreed with the Humane Society and vacated the
    2011 Rule, concluding that the Endangered Species Act does
    not permit the Service to designate a segment only to
    immediately delist it. See Humane Society of the U.S. v. Jewell,
    
    76 F. Supp. 3d 69
    , 110 (D.D.C. 2014). While the district court
    agreed that the statutory text was ambiguous, the court
    concluded that the Service’s interpretation was unreasonable
    given the structure, history, and purpose of the Act. 
    Id. at 110–
    113. In the district court’s view, the distinct population
    segment designation could only function as a “one-way
    ratchet,” allowing the Service to provide more, but not less,
    protection for a species. 
    Id. at 112.
    The district court also rejected the Service’s argument that
    it was simply revising the prior Minnesota wolf listing when it
    created the Western Great Lakes segment. The court explained
    that the Minnesota wolves had never been listed as a segment,
    and that the newly created segment altered the original
    geographic boundaries of the Minnesota wolf population.
    Humane 
    Society, 76 F. Supp. 3d at 114
    –115.
    The district court further concluded that the rule was
    arbitrary and capricious because the Service failed to address
    how large losses in the gray wolf’s historical range affected the
    determination that the Western Great Lakes segment was not
    endangered or threatened. Humane 
    Society, 76 F. Supp. 3d at 128
    –132.
    Finally, the district court held that the rule was invalid
    because the Service failed to adequately consider the threat to
    wolves from disease and human-caused mortality and the
    15
    insufficiency of state regulatory measures to protect the wolves
    after delisting. Humane 
    Society, 76 F. Supp. 3d at 132
    –134.
    The district court accordingly vacated the rule. 
    Id. at 136–137.
    II
    The Service’s listing determinations are subject to review
    under Section 706 of the APA, 5 U.S.C. § 706. See American
    Wildlands v. Kempthorne, 
    530 F.3d 991
    , 997 (D.C. Cir. 2008).
    Under that standard, we must overturn an agency decision if it
    is “arbitrary, capricious, an abuse of discretion, or otherwise
    not in accordance with law.” 5 U.S.C. § 706(2)(A).
    We review the Service’s interpretation of the Endangered
    Species Act under the familiar two-step Chevron framework.
    See Chevron U.S.A., Inc. v. Natural Resources Def. Council,
    Inc., 
    467 U.S. 837
    (1984). First, we apply the “traditional tools
    of statutory construction” to determine whether Congress has
    directly spoken to the question at issue. 
    Id. at 842–843
    & n.9;
    Central United Life Ins. v. Burwell, 
    827 F.3d 70
    , 73 (D.C. Cir.
    2016). If the statute’s meaning is clear, the inquiry ends and
    “we must give effect to the unambiguously expressed intent of
    Congress.” Secretary of Labor, Mine Safety & Health Admin.
    v. National Cement Co. of Cal., 
    494 F.3d 1066
    , 1073 (D.C. Cir.
    2007) (internal quotation marks and citation omitted). If,
    however, “the statute is silent or ambiguous with respect to the
    specific issue,” then we will defer to the agency’s considered
    interpretation of the statute if it is “reasonable.” Abington
    Crest Nursing & Rehab. Ctr. v. Sebelius, 
    575 F.3d 717
    , 719
    (D.C. Cir. 2009) (internal quotation marks and citation
    omitted); see also United States v. Mead Corp., 
    533 U.S. 218
    ,
    227–229 (2001).
    The central dispute in this case is whether the Endangered
    Species Act permits the Service to carve out of an already-
    16
    listed species a “distinct population segment” for the purpose
    of delisting that segment and withdrawing it from the Act’s
    aegis. We hold that the Act permits such a designation, but
    only when the Service first makes the proper findings.
    A
    This question of statutory interpretation starts with the
    Endangered Species Act’s plain text. The Act extends its
    protections to an endangered or threatened “species,” and then
    defines such protected species to include “any distinct
    population segment of any species of * * * wildlife[.]” 16
    U.S.C. § 1532(16). The identification and application of the
    Act to “distinct population segment[s]” thus falls
    straightforwardly within the Service’s wheelhouse. That much
    cannot be textually disputed.
    The tougher question is whether that distinct population
    segmentation process is, as the district court ruled, a one-way
    ratchet that only allows the Service to extend the Act’s
    protections to newly recognized groupings. See Humane
    
    Society, 76 F. Supp. 3d at 112
    . Or can the Service, even after
    a species as a whole has been identified as endangered or
    threatened, cleave out a subset of that already-listed species for
    delisting based on the segment’s recovery (or uplisting if it has
    become distinctly imperiled)? Said another way, once a
    species has been listed, must any changes in its listing status
    occur species-wide or can the species and its status be
    dissevered? As to that question, the statutory text is murkier.
    The Endangered Species Act quite plainly allows—
    actually, requires—the Service to periodically revisit and, as
    warranted, revise the status of a listed species. Section
    1533(c)(1) directs the Service to, “from time to time revise
    each list * * * to reflect recent determinations, designations,
    17
    and revisions.” 16 U.S.C. § 1533(c)(1); see 
    id. § 1533(a)(1),
    (b)(1)(A). And Section 1533(c)(2) separately directs the
    Service to “conduct, at least once every five years, a review of
    all [then-listed] species,” and to “determine on the basis of such
    review whether any such species should—(i) be removed from
    such list; (ii) be changed in status from an endangered species
    to a threatened species; or (iii) be changed in status from a
    threatened species to an endangered species.”                   
    Id. § 1533(c)(2)(A),
    (B). Each decision made under those two
    statutory provisions must rely upon the five statutorily
    designated criteria for listing and the best available scientific
    and commercial data.           
    Id. § 1533(c)(1),
    (2); see 
    id. § 1533(a)(1),
    (b)(1)(A).
    Nothing in that statutory language forbids the recognition
    of recovered distinct population segments within a listed
    species. The Secretary’s authority to revise a listing under
    Section 1533(c)(1) is generally unconditioned, as long as the
    underlying determination on which the revision is based (here,
    the finding of a distinct population segment) is grounded in the
    five statutory listing factors and the best available scientific and
    commercial data. See 16 U.S.C. § 1533(c)(1). To be sure,
    subsection (c)(1) cross-references the best-evidence
    requirement of Section 1533(b)(1)(A), which in turn directs the
    Service to “make determinations * * * after conducting a
    review of the status of the species,” 
    id. § 1533(b)(1)(A)
    (emphasis added). But that leaves textually unanswered the
    central question of whether a review of “the species” can itself
    result in the identification of a distinct population segment.
    Section 1533(c)(2)’s quinquennial review provision offers
    some textual support for the Humane Society’s argument that
    a change in status must be made for the species as listed.
    Subsection (c)(2) requires reconsideration of whether “such
    species” as “included in a list” that is “in effect at the time of
    18
    such review” should be changed from endangered to
    threatened, changed from threatened to endangered, or
    removed from the list entirely. 16 U.S.C. § 1533(c)(2)
    (emphasis added). “[S]uch species” would seem to require
    review of the species’ status as listed.
    But while that reading of the statute would be reasonable,
    it is not ineluctable. To begin with, while subsection (c)(2)
    prescribes what decisions the Service must make, its text does
    not foreclose the Service from making additional status
    decisions. In other words, nothing in the statutory language
    indicates that the mandated decisions are a ceiling capping the
    Service’s authority rather than just a minimum-requirements
    floor. In addition, subsection (c)(2) does not detract from the
    Service’s more open-ended revision authority under subsection
    (c)(1).
    The long and the short of all this is that the text of the
    Endangered Species Act does not itself answer the question
    whether the Service can designate a distinct population
    segment from within an already-listed species.
    B
    Because the statute is “silent or ambiguous with respect to
    the specific issue” at hand, the question before this court
    becomes whether the Service’s interpretation is “based on a
    permissible construction of the statute.” United States Sugar
    Corp. v. EPA, 
    830 F.3d 579
    , 605 (D.C. Cir. 2016) (quoting
    
    Chevron, 467 U.S. at 842
    –843). Generally, a “‘reasonable’
    explanation of how an agency’s interpretation serves the
    statute’s objectives is the stuff of which a ‘permissible’
    construction is made[.]” Northpoint Tech., Ltd. v. FCC, 
    412 F.3d 145
    , 151 (D.C. Cir. 2005) (citation omitted). “[A]n
    explanation that is ‘arbitrary, capricious, or manifestly contrary
    19
    to the statute,’ however, is not.” 
    Id. (quoting Chevron,
    467
    U.S. at 844). Accordingly, this court must determine whether
    the Service “has advanced a reasonable explanation for its
    conclusion that the regulations serve * * * [the Act’s]
    objectives,” 
    Chevron, 467 U.S. at 863
    , and whether that
    “interpretation * * * is at least reasonable in light of any
    ambiguities in the statute[,]” District of Columbia. v.
    Department of Labor, 
    819 F.3d 444
    , 449 (D.C. Cir. 2016). See
    United States Sugar 
    Corp., 830 F.3d at 608
    (regulation must
    reflect a “permissible reading” of the statute).
    The Service’s interpretation of Section 1533(c)(1) as
    allowing for the designation of a distinct population segment
    within a listed species is a reasonable reading of statutory text
    and—when properly undertaken, see Part II.C, infra—does not
    contravene the purposes of the Endangered Species Act.
    With respect to the statutory language, the Service’s
    position makes textual sense because subsection (c)(1) itself
    expressly contemplates that new “designations” and
    “determinations” could intervene that would require
    “revis[ing]” an extant listing. 16 U.S.C. § 1533(c)(1).
    Furthermore, the listing of an animal at the species-wide level
    can reasonably be understood to include within it a listing of
    all subspecies and segments within that species. That is to say,
    the Service’s initial listing of all gray wolves in North America
    necessarily listed all possible segments and subspecies within
    that grouping. See Solicitor’s Opinion 7; 2011 Rule, 76 Fed.
    Reg. at 81,670, 81,683. So understood, the Service’s
    interpretation comports with Section 1533(c)(2)’s textual
    requirement that listing changes apply only to species that are
    already “included in a list * * * [that] is in effect,” at the time
    of the Service’s five-year status review, 
    id. § 1533(c)(2).
                                   20
    In addition, the statute requires the Service to attend to
    both parts of the listing process—the initial listing, and the
    revision or delisting—with equal care. After all, both
    subsections (c)(1) and (c)(2) require the Service to rely on the
    same factors and best evidence that were first used to list a
    species when downlisting, delisting, uplisting, or otherwise
    revising that species’ status. Nothing in the statutory text
    compels the Service to put a thumb on the scale in favor of
    listing, nor does the text require the Service to temporize when
    the best evidence indicates that a revision is warranted.
    Indeed, the statutory text leaves room for the Service, at
    the initial stage, to list most of a species as threatened, while
    dividing out a distinct population segment for listing as
    endangered based on its unique circumstances and conditions.
    That same language would also permit the Service at the outset
    to list a segment as threatened even if the remainder of the
    taxon is endangered. See 16 U.S.C. § 1532(16) (defining
    “species” in non-exhaustive terms); cf. Modesto Irrigation
    Dist. v. Gutierrez, 
    619 F.3d 1024
    , 1031–1032 (9th Cir. 2010)
    (Service need not place interbreeding populations of a species
    in the same distinct population segment); Trout Unlimited v.
    Lohn, 
    559 F.3d 946
    , 959–961 (9th Cir. 2009) (upholding the
    Service’s practice of distinguishing between geographically
    co-located hatchery and natural populations of the same
    taxonomic species when listing).
    Because the statutory text and purposes can be read to
    permit such a divided listing on the front end of the listing
    process, the Service likewise can reasonably read the statute to
    permit similar determinations at the revision stage. The
    statutory text does not have to be treated like a one-way street
    leading only to uplisting.
    21
    The Service’s position is also consonant with the purposes
    of the Endangered Species Act, which is to devote needed
    resources to the protection of endangered and threatened
    species, while abating the Act’s comprehensive protections
    when a species—defined to include a distinct population
    segment—is recovered. See, e.g., 16 U.S.C. § 1531 (statutory
    purpose is to provide for the conservation of species when they
    are “endangered” or “threatened”); 
    id. § 1533(b)(2)
    (directing
    the Service to take into account the “economic impact, the
    impact on national security, and any other relevant impact”
    when designating “any particular area as critical habitat”);
    Defenders of Wildlife v. Norton, 
    258 F.3d 1136
    , 1144 (9th Cir.
    2001) (noting Congress’s desire to allow the Service “more
    flexibility in [its] approach to wildlife management”). The
    Service’s interpretation ensures that the most resources can be
    brought to bear where a species continues to be threatened or
    endangered. See Solicitor’s Opinion 18–19; 2011 Rule, 76
    Fed. Reg. at 81,670, 81,683. In that regard, the Act’s direction
    to the Service to evaluate the status of not just species, but
    subspecies and segments, 16 U.S.C. § 1532(16), signals
    Congress’s intent to target the Act’s provisions where needed,
    rather than to require the woodenly undifferentiated treatment
    of all members of a taxonomic species regardless of how their
    actual status and condition might change over time. 3
    Another purpose of the Endangered Species Act is to foster
    state cooperation in the conservation of threatened or
    endangered species. See 16 U.S.C. § 1531(a)(5) (One purpose
    3
    See also 16 U.S.C. § 1539(j) (providing for the discretionary
    use of experimental populations in species recovery); 
    id. § 1539(a)
    (allowing the Service to issue permits for the “taking” of listed
    species in specified circumstances); Loggerhead Turtle v. Council of
    Volusia Cty., 
    148 F.3d 1231
    , 1260 (11th Cir. 1998) (describing
    “flexible” nature of the Service’s authority to allow “incidental
    takes”).
    22
    of the Act is “encouraging the States * * * to develop and
    maintain conservation programs which meet national and
    international standards[.]”); see also Solicitor’s Opinion 16–17
    (“Removing [Endangered Species Act] protections for
    recovered [Distinct Population Segments] of listed species
    reinforces the strong public policy goal of federal-State
    cooperation[.]”); 2011 Rule, 76 Fed. Reg. at 81,670, 81,683
    (incorporating the views expressed in the Solicitor’s Opinion). 4
    Because the locations of distinct population segments not
    uncommonly correspond with geographical lines, empowering
    the Service to alter the listing status of segments rewards those
    States that most actively encourage and promote species
    recovery within their jurisdictions. On the other hand,
    continuing to rigidly enforce the Act’s stringent protections in
    the face of such success just because recovery has lagged
    elsewhere would discourage robust cooperation. The Service’s
    interpretation thus reasonably “encourage[s] the States * * *
    through * * * a system of incentives.” 16 U.S.C. § 1531(a)(5).
    The Humane Society argues that Service action under the
    Act “must be, first and foremost, to provide protections to
    endangered or threatened species.” Humane Society’s Br. 33.
    True enough. But that premise does nothing to answer the
    4
    See also 16 U.S.C § 1533(b)(1)(A) (directing the Service to
    take into account “efforts, if any, being made by any State or foreign
    nation, or any political subdivision of a State or foreign nation, to
    protect such species, whether by predator control, protection of
    habitat and food supply, or other conservation practices, within any
    area under its jurisdiction, or on the high seas,” when determining
    whether to list a species).
    23
    specific question of whether the Service is permitted to tailor
    its protections to where they are most needed.
    Relatedly, the Humane Society argues that designating a
    segment to delist it violates the Service’s formal Segment
    Policy, 61 Fed. Reg. at 4,724–4,725. Aspects of that Policy
    certainly underscore its protective purpose. The Service has
    explained that the identification of distinct population
    segments should “be aimed at carrying out the purposes of the
    Act,” including “to provide a means whereby the ecosystems
    upon which endangered species and threatened species depend
    may be conserved, [and] to provide a program for the
    conservation of such endangered species and threatened
    species.” 
    Id. at 4,722
    (internal quotation mark and citation
    omitted).     Indeed, some of the Policy’s criteria for
    “significance”—which a population must possess to qualify as
    a segment—would seem to most often be relevant to enhancing
    protections for animals. For example, it would not make much
    sense to downlist or delist a population that “represents the only
    surviving natural occurrence of a taxon that may be more
    abundant elsewhere as an introduced population outside its
    historic range.” 
    Id. at 4,725.
    On the other hand, other aspects of the Segment Policy
    plainly work in both the listing and delisting directions. See
    Segment Policy, 61 Fed. Reg. at 4,722 (describing segments as
    being used “for the purposes of listing, delisting, and
    reclassifying species”) (emphasis added); 
    id. at 4,725
    (referring
    to the enumerated segment factors as “apply[ing] similarly for
    addition to the lists[,] * * * reclassification, and removal from
    the lists”) (emphasis added); 
    id. (identifying the
    Segment
    Policy as guiding “the evaluation of distinct vertebrate
    population segments for the purposes of listing, delisting, and
    reclassifying under the Act”) (emphasis added).
    24
    The Solicitor’s Opinion, formally adopted by the Service,
    has now explicitly interpreted the Act to allow the segment tool
    for delisting. See Solicitor’s Opinion 3–5; 2011 Rule, 76 Fed.
    Reg. at 81,670, 81,683. See also Encino Motorcars, LLC v.
    Navarro, 
    136 S. Ct. 2117
    , 2125 (2016) (“Agencies are free to
    change their existing policies so long as they provide a
    reasoned explanation for the change.”).
    The Humane Society also argues that designating a
    segment to delist it violates the specific process set out in the
    Segment Policy, 61 Fed. Reg. at 4,725. That Policy identifies
    three factors to be considered in designating and listing a
    segment: the “discreteness,” “significance,” and “conservation
    status” of a population. 
    Id. The Humane
    Society reads that
    provision to require findings that a population is discrete,
    significant, and has a conservation status of threatened or
    endangered before the Service can designate it.
    But the far more natural reading of the Policy is that it only
    requires a determination that the potential segment is
    threatened or endangered prior to listing, not prior to the
    designation of the segment itself. See Segment Policy, 61 Fed.
    Reg. at 4,725. The Policy specifically sets out identification of
    the segment’s conservation status as an independent step that
    follows after a segment has been identified as a distinct
    population segment because of its discreteness and
    significance. See 
    id. (“Status: If
    a population segment is
    discrete and significant (i.e., it is a distinct population segment)
    its evaluation for endangered or threatened status will be based
    on the Act’s definitions of those terms and a review of the
    factors enumerated in [Section 1533(a)].”) (second emphasis
    25
    added). The Service’s decision in this case thus did not
    contradict its Segment Policy. 5
    * * * * *
    “When it enacted the [Endangered Species Act], Congress
    delegated broad administrative and interpretive power to the
    [Service].” Babbitt v. Sweet Home Chapter of Communities for
    a Great Oregon, 
    515 U.S. 687
    , 708 (1995). And “[t]he task of
    defining and listing endangered and threatened species requires
    an expertise and attention to detail that exceeds the normal
    province of Congress.” 
    Id. Given the
    ambiguity of the
    statutory text, the Humane Society’s proffered interpretation of
    the Act as favoring the use of segments in a protective manner
    may very well be reasonable. But our task under Chevron is
    not to pick from amongst reasonable options. Our task is
    simply to determine whether the Service’s interpretation of the
    ambiguous language is reasonable. We hold that the Service
    permissibly concluded that the Endangered Species Act allows
    the identification of a distinct population segment within an
    already-listed species, and further allows the assignment of a
    different conservation status to that segment if the statutory
    criteria for uplisting, downlisting, or delisting are met.
    5
    Because the Service has the better and more natural reading
    of its Segment Policy, we do not address whether the Service’s
    interpretation is owed deference under Auer v. Robbins, 
    519 U.S. 452
    (1997). Cf. Baptist Mem’l Hosp.-Golden Triangle v. Sebelius, 
    566 F.3d 226
    , 228 (D.C. Cir. 2009) (“We need not tackle the question of
    [Auer] deference: We agree with the Board’s interpretation of its
    Instructions regardless of what, if any, deference we owe it in this
    case.”); see also Talk America, Inc. v. Michigan Bell Tel. Co., 
    564 U.S. 50
    , 67 (2011) (Scalia, J., concurring) (“In this suit I have no
    need to rely on Auer deference, because I believe the [agency’s]
    interpretation is the fairest reading of the orders in question.”).
    26
    C
    Holding that the Service has the legal authority to identify
    a distinct population segment from within an already-listed
    species does not mean it did so properly here. In fact, it did
    not. The fundamental error in the Service’s decision is that, in
    evaluating whether gray wolves in the Western Great Lakes
    region are a “distinct” population segment, the Service failed
    to address the impact that extraction of the segment would have
    on the legal status of the remaining wolves in the already-listed
    species. More specifically, the Service cannot find that a
    population segment is distinct—in the Service’s words, that it
    is severable because it is “discrete” and “significant”—without
    determining whether the remnant itself remains a species so
    that its own status under the Act will continue as needed.
    1
    The Endangered Species Act’s text requires the Service,
    when reviewing and redetermining the status of a species, to
    look at the whole picture of the listed species, not just a
    segment of it. Section 1533(c)(2)(A) requires that the review
    cover the “species included in a list.”               16 U.S.C.
    § 1533(c)(2)(A); see also 
    id. § 1533(c)(1),
    (b)(1)(A) (directing
    the Service, when revising the status of a species, to “make [its]
    determinations * * * after conducting a review of the status of
    the species” as listed) (emphasis added); see also 
    id. § 1533(c)(2)(B).
    As the Service itself argues, that review can
    reasonably be read to include any and all of the composite
    segments or subspecies that might be included within a
    taxonomically listed species. See Solicitor’s Opinion 7–8 &
    n.10; 2011 Rule, 76 Fed. Reg. at 81,670, 81,683. Thus, when
    a species is already listed, the Service cannot review a single
    segment with blinders on, ignoring the continuing status of the
    species’ remnant. The statute requires a comprehensive review
    27
    of the entire listed species and its continuing status. Having
    started the process, the Service cannot call it quits upon finding
    a single distinct population segment.
    The Service’s definition of a “distinct population segment”
    confirms the point. See Segment Policy, 61 Fed. Reg. at 4,725.
    The Service’s two critical criteria for such a segment are
    “discreteness” and “significance.” 
    Id. Both of
    those factors
    must be met before a segment can be recognized.
    To start, the Service looks at the “[d]iscreteness of the
    population segment in relation to the remainder of the species
    to which it belongs.” Segment Policy, 61 Fed. Reg. at 4,725.
    More specifically, to be distinct, a segment must be “markedly
    separated” out “from other populations of the same taxon as a
    consequence of physical, physiological, ecological, or
    behavioral factors.” 
    Id. Those two
    factors clearly envision a
    comparative analysis of a potential segment to the remnant and
    consideration of the segment’s independent severability. 6
    With respect to the “significance” part of the test, the
    Service looks to such factors as whether the segment:
    (i) persists in an “ecological setting” that is “unusual or unique
    for the taxon”; (ii) is the “only surviving natural occurrence of
    a taxon”; (iii) has genetic characteristics that are “markedly”
    different from the rest of the taxon; or (iv) would cause a
    “significant gap” in the taxon’s range if lost. Segment Policy,
    61 Fed. Reg. at 4,725. Each of those factors measures a
    potential segment’s “significance” in relation to the “taxon.”
    That means that an evaluation of “significance” presupposes
    that there is a still-existing taxon against which to compare the
    6
    International borders can also sometimes help to identify a
    discrete population segment. Segment Policy, 61 Fed. Reg. at 4,725.
    That consideration is not at issue in this case.
    28
    potential segment. Indeed, without an evaluation of the taxon
    (both pre- and post-designation of the proposed segment), the
    Service could not in any meaningful way evaluate the proposed
    segment’s significance to that taxon.
    Requiring the Service to look at the implications for both
    the segment and the remnant during the delisting, uplisting, or
    downlisting process thus flows naturally from the Endangered
    Species Act’s text and the Service’s own Segment Policy.
    Even more importantly, omitting analysis of the effect of
    designation on the already-listed species would divest the
    extant listing of legal force. The segment-designation process
    is meant to be “sparing[]” in its use. Segment Policy, 61 Fed.
    Reg. at 4,724. Yet the Service’s disregard of the remnant’s
    status would turn that sparing segment process into a backdoor
    route to the de facto delisting of already-listed species, in open
    defiance of the Endangered Species Act’s specifically
    enumerated requirements for delisting. See 16 U.S.C.
    § 1533(a)(1) (listing five mandatory criteria for altering a
    listing). Accordingly, as a matter of plain statutory design, the
    act of designating a segment cannot in one fell swoop make an
    already-listed species an unlisted and unlistable non-species,
    “sidestep[ping]” the process “Congress has plainly” prescribed
    for delisting. See Natural Resources Def. Council v. EPA, 
    489 F.3d 1364
    , 1372 (D.C. Cir. 2007); see also Whitman v.
    American Trucking Ass’ns, 
    531 U.S. 457
    , 485 (2001) (“[An
    agency] may not construe the statute in a way that completely
    nullifies textually applicable provisions meant to limit its
    discretion.”). Instead, the Service must make it part and parcel
    of its segment analysis to ensure that the remnant, if still
    endangered or threatened, remains protectable under the
    Endangered Species Act.
    29
    2
    In designating the Western Great Lakes wolves as a
    distinct population segment, the Service looked only at the
    characteristics of the Western Great Lakes segment in a
    vacuum, ignoring the second step of determining whether both
    the segment and the remainder of the already-listed wolves
    would have mutually independent statuses as species.
    Prior to the 2011 Rule designating the Western Great
    Lakes segment, the Service had made two listings of gray
    wolves: those in Minnesota that were found to be threatened,
    and those wolves in the lower forty-eight states outside of
    Minnesota that were determined to be an endangered species.
    When the Service attempted to carve the Western Great Lakes
    segment out of the latter, it left the remnant of that already-
    statutorily-protected group in legal limbo without any
    determination that the gray wolves in the continental United
    States outside of the Western Great Lakes segment were
    themselves a species, subspecies, or segment that could
    continue to be protected under the Endangered Species Act.
    Certainly “gray wolves outside the Western Great Lakes
    segment” have never been recognized as a taxonomic species.
    The Service also failed to analyze whether “gray wolves
    outside the Western Great Lakes segment” are either a
    subspecies or a segment. 7 Absent such a determination, the
    Service has left entirely unexplained how the remaining
    wolves’ existing endangered status would continue. Nor did
    the Service make any finding that the remnant was no longer
    endangered under the statutory listing criteria.
    7
    We take no position on whether such a designation by the
    Service would be appropriate. See Florida Power & Light Co. v.
    Lorion, 
    470 U.S. 729
    , 744 (1985).
    30
    Worse still, the Service has announced that, with the
    Western Great Lakes segment carved out, the remnant is no
    longer a protectable “species” and has proposed its delisting for
    that reason alone. See Removing the Gray Wolf (Canis lupus)
    From the List of Endangered and Threatened Wildlife and
    Maintaining Protections for the Mexican Wolf (Canis lupus
    baileyi) by Listing It as Endangered, 78 Fed. Reg. 35,664,
    35,668 (June 13, 2013) (“We conclude that the current C. lupus
    [gray wolf] entity is not a valid species under the Act and now
    propose to remove this entity from the List[.]”). The Service
    did not deny that position at oral argument. See Oral Arg. Tr.
    85–90.
    The Service’s power is to designate genuinely discrete
    population segments; it is not to delist an already-protected
    species by balkanization. The Service cannot circumvent the
    Endangered Species Act’s explicit delisting standards by riving
    an existing listing into a recovered sub-group and a leftover
    group that becomes an orphan to the law. Such a statutory
    dodge is the essence of arbitrary-and-capricious and ill-
    reasoned agency action. See Ragsdale v. Wolverine World
    Wide, Inc., 
    535 U.S. 81
    , 91–92, 94 (2002) (invalidating agency
    action that constituted an “end run around important [statutory]
    limitations” and thus “contravene[d] Congress’ will” and
    “subvert[ed] the careful balance” of the statute).
    The Service argues in the alternative that it did not
    designate a new segment, but rather only revised the 1978
    Minnesota gray wolf segment and then delisted it. We are
    doubtful that the Service’s action can be fairly characterized as
    a revision, especially given the fact the purported revision
    roped-in wolf populations outside of the original Minnesota
    population. See 2011 Rule, 76 Fed. Reg. at 81,678–81,679,
    81,716; 1978 Rule, 43 Fed. Reg. at 9,608 (“There is also a
    group [of wolves] on Isle Royale in Lake Superior, and
    31
    possibly a few scattered individuals in northern Michigan and
    Wisconsin.”). By bringing within the scope of the segment
    those outside-Minnesota wolves, the Service’s “revision” of
    the Minnesota gray wolf segment is in fact a revamping of the
    entire gray wolf listing, including the non-Minnesota
    population listing. But we need not decide that question.
    Whether labeled a revision or a segment-designation, the flaw
    is the same: the failure to address the status of the remnant is
    fatal.
    III
    Under the Endangered Species Act, the determination of a
    species’ endangered or threatened status turns on the threats
    that the species faces “throughout all or a significant portion of
    its range.” 16 U.S.C. § 1532(6), (20). The Service concluded
    that “range” refers to the species’ current range at the time its
    status is evaluated or reevaluated for listing. See 2011 Rule, 76
    Fed. Reg. at 81,721–81,722. The district court held that the
    Service’s decision to delist the Western Great Lakes segment
    failed to adequately address the wolves’ loss of historical
    range. Humane 
    Society, 76 F. Supp. 3d at 128
    –132. Because
    the Service’s interpretation of “range” as focusing on “current
    range” is reasonable, we uphold it. But because the Service
    categorically excluded the effects of loss of historical range
    from its analysis, we hold that the Service’s conclusion about
    the ongoing threat to the Western Great Lakes segment within
    its current range was insufficiently reasoned, and therefore
    arbitrary and capricious.
    A
    Under Chevron, we ask first whether the Endangered
    Species Act speaks directly to the meaning of “range” and, if it
    does not, we must evaluate the reasonableness of the Service’s
    interpretation. 
    See 467 U.S. at 842
    –843.
    32
    The Endangered Species Act does not itself define
    “range.”     See 16 U.S.C. § 1532.            The definitions of
    “endangered” and “threatened” species, however, do use the
    present tense “is” to refer to the status of the species within its
    range. 
    Id. § 1532(6),
    (20). That seems to accord with the
    Service’s position that “range” refers to “current range.” See
    Sherley v. Sebelius, 
    644 F.3d 388
    , 394 (D.C. Cir. 2011) (“The
    use of the present tense in a statute strongly suggests it does not
    extend to past actions.”). But see McNeill v. United States, 
    563 U.S. 816
    , 821–822 (2011) (Congress has “used the present
    tense to refer to past convictions”).
    Still, focusing on verb tense does not get the Service very
    far. That is because the placement of “is” in the definitions
    seems most naturally to require that the species currently be
    endangered or threatened within its range, not to dictate the
    temporal scope of geographical evidence the Service is to
    consider. A species can be found to be endangered now—“is
    in danger of extinction,” 16 U.S.C. § 1532(6) (emphasis
    added)—based just as easily on threats to the species
    throughout its historical range as on threats throughout its
    contemporary range. Cf. Defenders of Wildlife v. Norton, 
    258 F.3d 1136
    , 1145 (9th Cir. 2001) (“[A] species can be extinct
    ‘throughout * * * a significant portion of its range’ if there are
    major geographical areas in which it is no longer viable but
    once was.”) (second alteration in original).
    Outside of its use in the definitions of “endangered” and
    “threatened” species, “range” appears only three times in the
    Act. The term first appears in Section 1533(a), which lists “the
    present or threatened destruction, modification, or curtailment
    of [a species’] habitat or range,” as one of several factors for
    the Service to consider in determining “endangered” or
    “threatened” status. 16 U.S.C. § 1533(a)(1)(A). The term
    appears a few subsections later in Section 1533(c), which
    33
    mandates that the listing of a species as endangered or
    threatened shall “specify with respect to each * * * species
    over what portion of its range it is endangered or threatened,
    and specify any critical habitat within such range.” 
    Id. § 1533(c)(1).
    Neither of those usages casts material light on
    the meaning of “range” because the two references are as
    textually indeterminate as the initial use of the term in Section
    1532.
    The third place that “range” appears is in Section 1539(j),
    which provides that the Secretary may authorize the release of
    any population of an endangered or threatened species “outside
    the current range of such species if the Secretary determines
    that such release will further the conservation of such species.”
    16 U.S.C. § 1539(j)(2)(A). That provision cuts both ways. On
    the one hand, it could be argued that, if “range” already means
    current range, then the adjectival addition of “current” in
    Section 1539(j) would be redundant. On the other hand, the
    use of “current range” in Section 1539(j) could also be read to
    corroborate the Service’s view, since “current range” in
    Section 1539(j) may refer to the listed range of the endangered
    or threatened species. See 
    id. § 1539(j)(2)(A).
    Dictionary definitions do not illuminate the meaning of
    “range” either. As a biological and zoological term of art,
    “range” is commonly defined as a geographical reference to the
    physical area in which a species lives or occurs. See, e.g., 8
    THE OXFORD ENGLISH DICTIONARY 139 (def. 7) (1933)
    (defining “range” as: “[t]he geographical area over which a
    certain plant or animal is distributed”). The most that can be
    said is that such dictionary definitions employ the present
    tense. But that may reflect the nature of dictionary definitions
    34
    generally, rather than suggest any contextual meaning within
    the Endangered Species Act. 8
    Accordingly, traditional rules of statutory construction do
    not answer the question of whether “range” means current or
    historical range. Indeed, the Service and the Humane Society
    both acknowledge that the Act leaves open the possibility that
    “range” may refer to either current or historical range. See
    Service’s Br. 68–69; Humane Society’s Br. 47–48. 9 The
    question then becomes whether the Service’s interpretation of
    “range” as “current range” “is based on a permissible
    construction of the statute.” Mayo Found. for Med. Educ. &
    Research v. United States, 
    562 U.S. 44
    , 54 (2011) (quoting
    
    Chevron, 467 U.S. at 843
    ). It is.
    Although the statute itself does not indicate the meaning
    of “range,” the Service’s interpretation is at least consistent
    with the Endangered Species Act’s use of the present tense in
    provisions discussing the species’ range, 16 U.S.C. § 1532(6),
    (20). And it also accords with Section 1539(j)(2)(A)’s use of
    “current range” in reference to a species’ listed range. In
    addition, focusing on the species’ survival in the range it
    currently occupies is consonant with the purposes of the
    Endangered Species Act, because the threats that a species
    confronts where it currently lives often affect its continued
    8
    None of the parties suggests that legislative history illuminates
    the meaning of “range.”
    9
    Other courts have recognized the ambiguity of the broader
    statutory phrase “in danger of extinction throughout * * * a
    significant portion of its range,” see Defenders of 
    Wildlife, 258 F.3d at 1141
    , or “significant portion of its range,” see Colorado River
    Cutthroat Trout v. Salazar, 
    898 F. Supp. 2d 191
    , 201–203 (D.D.C.
    2012); WildEarth Guardians v. Salazar, 
    741 F. Supp. 2d 89
    , 99–100
    (D.D.C. 2010).
    35
    survival the most and thus bear influentially on whether it
    should be listed. See 2011 Rule, 76 Fed. Reg. at 81,722–81,723
    (discussing threats in areas where the Western Great Lakes
    wolf population currently lives).
    For those reasons, we conclude that the Service’s
    interpretation of “range” to focus on a species’ current range is
    a reasonable interpretation of the Act.
    B
    As with the Service’s designation of distinct population
    segments, the rub in this case is not with the Service’s
    interpretation of the statute, but with its application of the
    statute to the record at hand. While analysis of the
    reasonableness of agency action “under Chevron Step Two and
    arbitrary and capricious review is often the same,”
    Pharmaceutical Research & Mfrs. of America v. Federal Trade
    Comm’n, 
    790 F.3d 198
    , 209 (D.C. Cir. 2015) (internal
    quotation marks and citation omitted), the Venn diagram of the
    two inquiries is not a circle. The question thus remains whether
    the agency arbitrarily and capriciously “‘failed to consider an
    important aspect of the problem’ it faces.” SecurityPoint
    Holdings, Inc. v. Transportation Sec. Admin., 
    769 F.3d 1184
    ,
    1187 (D.C. Cir. 2014) (quoting Motor Vehicle Mfrs. Ass’n of
    the U.S. v. State Farm Mut. Auto. Ins. Co., 
    463 U.S. 29
    , 43
    (1983)).
    We hold that the Service’s analysis of the status of the
    Western Great Lakes segment within its current range wrongly
    omitted all consideration of lost historical range. Just because
    the Endangered Species Act does not compel the Service to
    interpret “range” to mean historical range, that does not mean
    that the Service can brush off a substantial loss of historical
    range as irrelevant to the species’ endangered or threatened
    36
    status. So says the Service itself: The Service’s Range Policy
    is explicit that a species may be “endangered or threatened
    throughout all or a significant portion of its current range
    because [a] loss of historical range is so substantial that it
    undermines the viability of the species as it exists today.”
    Range Policy, 79 Fed. Reg. at 37,584 (emphasis added).
    That is an eminently sensible approach. Range loss can
    “result[] in a species for which distribution and abundance is
    restricted, gene flow is inhibited, or population redundancy is
    reduced to such a level that the entity is now vulnerable to
    extinction or likely to become so within the foreseeable future
    throughout all or a significant portion of its current range.”
    Range Policy, 79 Fed. Reg. at 37,584. In addition, “a species
    with a reduced range is at greater risk of all or most of its
    populations being affected by a catastrophic event such as a
    hurricane or fire.” 
    Id. In other
    words, an adequate evaluation of the threats
    confronting the survival of a species within its current range
    requires looking at more than just the current moment in time.
    The Service, consistent with its own Range Policy, also needs
    to consider the scope of the species’ historical range, and the
    impact that material contraction or relocation might indicate for
    survival within a currently constricted or confined range.
    There is, moreover, no question in this case that “gray
    wolves have been extirpated from most of the southern portions
    of their historical North American range.” 2011 Rule, 76 Fed.
    Reg. at 81,672. The Humane Society estimates that 95% of the
    gray wolf’s historical range has disappeared. Humane
    Society’s Br. 48, 50. The Service does not dispute that figure.
    Despite immense losses in the gray wolves’ historical
    range—including the historical range of those wolves now
    occupying the Western Great Lakes area—the Service nowhere
    37
    analyzed the impact of that loss on the survival of the gray
    wolves as a whole, the gray wolves remnant, or the Western
    Great Lakes segment. Such a failure to address “an important
    aspect of the problem” that is factually substantiated in the
    record is unreasoned, arbitrary, and capricious decisionmaking.
    State 
    Farm, 463 U.S. at 43
    ; see also AEP Tex. N. Co. v. Surface
    Transp. Bd., 
    609 F.3d 432
    , 441 (D.C. Cir. 2010) (agency acted
    arbitrarily and capriciously when it “failed to address the
    unique circumstances of” an issue).
    The Service does not deny the gap in its analysis. Instead,
    the Service points to its determination that the Western Great
    Lakes segment would remain viable in key portions of the
    Western Great Lakes area. See 2011 Rule, 76 Fed. Reg. at
    81,722–81,723. That is a non sequitur. As the Range Policy
    explained, consideration of material changes in a species’
    historical range is critical to a reliable assessment of
    sustainability within the current range. So whatever the
    Service prognosticates about future viability in certain portions
    of the current range cannot be reliably reasoned if it was made
    in a historical vacuum. An important factor—the possible
    enduring consequences of significant loss of historical range—
    was left out of the analysis all together.
    The Service also argues that the Act does not require the
    restoration of a species to its entire historical range. See
    Service’s Reply Br. 27–29. Okay. But giving adequate
    consideration to the effects of large losses of historical range
    on a species’ survival going forward has nothing to do with
    where geographically a species must be restored. The only
    obligation at issue here is for the Service to contend with the
    implications of massive range loss for the species’ endangered
    or threatened status within its current environment.
    38
    Finally, we note that, in undertaking that omitted analysis
    on remand, the Service will have to grapple with predicate
    questions that the Service has evaded thus far, such as:
    •   Defining the physical boundaries of the relevant
    historical range, compare 2011 Rule, 76 Fed. Reg.
    at 81,672 (noting that “[g]ray wolves once lived
    throughout most of North America”), with 
    id. at 81,689
    (finding that this particular population of
    gray “wolves historically occupied the entire
    Midwest”), and 
    id. at 81,725
    (describing the gray
    wolf’s historical range as the entire “Holarctic”
    region); see also 
    id. at 81,687
    (noting that research
    into “whether gray wolves * * * historically
    occupied portions of the eastern United States is
    ongoing”); and
    •   Establishing the appropriate timeframe for
    measuring a species’ historical range, such as the
    enactment of the 1973 Endangered Species Act,
    the enactment of its predecessor statutes in 1966
    and 1969, the Nation’s founding, or some other
    date.
    In sum, because the undisputedly vast loss of historical
    range is a salient factor in determining the endangered or
    threatened status of the Western Great Lakes segment and the
    remnant population within their current ranges, the Service’s
    wholesale failure to address that factor renders the Service’s
    decision unreasoned, arbitrary, and capricious.
    39
    IV
    The Humane Society also argues that the final rule failed
    adequately (i) to explain why the wolf population’s combined
    mortality from humans and disease is not a continuing threat to
    the species’ existence, and (ii) to address the lack of adequate
    plan provisions or other protections for the gray wolves in the
    seven States that make up the Western Great Lakes area.
    Neither argument succeeds.
    A
    With respect to the combined threat to the gray wolves’
    survival from disease and human-caused death, the record
    reflects that the Service adequately wrestled with both
    problems and grounded its decision in substantial evidence.
    1
    With respect to disease mortality, the 2011 Rule addressed
    five diseases that afflict the Western Great Lakes gray wolves:
    canine parovirus, sarcoptic mange, lyme, dog louse, and canine
    distemper virus. The Rule also looked at the possibility of
    other diseases entering the wolf population. 2011 Rule, 76 Fed.
    Reg. at 81,694–81,698. The Service’s analysis was grounded
    in scientific literature specifically analyzing the history and
    impact of disease on the gray wolf population.
    For instance, the Service explained that there was “no
    evidence” that canine parovirus “caused a population decline
    or has had a significant impact on the recovery of the
    Minnesota wolf population.” 2011 Rule, 76 Fed. Reg. at
    81,694. While some studies suggested that canine parovirus
    had reduced pup survival from 1984 to 2004, the Service found
    that there had actually been an increase in pup survival since
    1995. 
    Id. Notably, data
    in Wisconsin showed only a single
    40
    pup death attributable to canine parovirus since 2001, 
    id., and no
    such deaths in Michigan, 
    id. at 81,695.
    With respect to sarcoptic mange, the Service determined
    that mange mortality was “stabilizing or perhaps declining in
    Wisconsin.” 2011 Rule, 76 Fed. Reg. at 81,695. The Service
    pointed to studies indicating that mange infection had not
    increased in Minnesota since 2003, and had in fact declined
    from 17% in 2006 to 10% in 2008. 
    Id. at 81,696.
    As for lyme
    disease and dog louse, the Service reported that there had been
    no confirmed deaths in the Minnesota wolf population from
    dog louse and no reports of clinical symptoms of lyme disease.
    
    Id. Finally, with
    respect to canine distemper virus, the Service
    relied on scientific studies that “predict periodic short-term
    declines * * * but no long-term threat to the wolf population”
    from the disease. 
    Id. The Service
    also acknowledged the possibility that new
    diseases might arise, but concluded there was no sufficiently
    concrete risk to threaten the gray wolf’s survival. 2011 Rule,
    76 Fed. Reg. at 81,696. In that regard, the Service explained
    that Minnesota’s, Michigan’s, and Wisconsin’s state plans all
    provided for the continued monitoring of dead wolves and
    testing of live-captured wolves and wolf feces to detect any
    new diseases that might require intervention. 
    Id. at 81,697.
    Looking at the collective threat from disease, the Service
    concluded that “the overall trend for wolf populations in the
    [Western Great Lakes segment] continues to be upward.” 
    Id. at 81,698.
    The Service added that delisting the wolves “will
    not significantly change the incidence or impacts of disease and
    parasites on these wolves.” 
    Id. The Service
    ’s judgment was corroborated through peer
    review by a veterinary pathologist specializing in wolf disease
    and mortality. The pathologist concluded that the proposed
    41
    rule “definitely contain[ed] an accurate, comprehensive
    synthesis of published and unpublished data on disease and
    predation threats to the Western Great Lakes * * * wolf
    populations.” J.A. 881. She further concurred that “wolf
    populations have grown despite introductions of new
    diseases,” and that “all evidence indicate[d] that [diseases] are
    not likely to endanger the [Western Great Lake] wolf
    populations if delisted.” 
    Id. 2 The
    Service’s analysis of human-caused mortality too was
    satisfactory. Human-caused mortality for wolves comes in
    three forms: fatal accidents (often involving vehicles), legal
    depredation programs, and intentional illegal killings.
    The Service’s 2011 Rule studied human-caused mortality
    in detail. The Service reviewed existing mortality data and
    acknowledged that humans were responsible for 56% of
    diagnosed deaths of radio-collared wolves in Wisconsin from
    1979 to 2009, 69% of such deaths in Minnesota from 1994 to
    2005, and 75% of such deaths in the Upper Peninsula of
    Michigan from 1960 to 1997. 2011 Rule, 76 Fed. Reg. at
    81,698–81,699.
    The Service nevertheless concluded that human-caused
    mortality was not a significant threat to the wolf’s survival, as
    shown by the resilient growth of the gray wolf population
    despite the human-caused deaths. “As long as other mortality
    factors do not increase significantly,” the Service concluded,
    and “monitoring is adequate to document, and if necessary
    counteract, the effects of excessive human-caused mortality
    should that occur, * * * [the] wolf population will not decline
    to nonviable levels” because of human-caused mortality. 2011
    Rule, 76 Fed. Reg. at 81,700 (citation omitted).
    42
    The Service further reasoned that delisting the segment of
    gray wolves would not affect the rate of human-caused
    mortality. That is because accidental and depredation deaths
    are most directly tied to the wolves’ proximity to areas densely
    populated by humans. See 2011 Rule, 76 Fed. Reg. at 81,700
    (“[A] continuing increase in wolf mortalities from vehicle
    collisions, both in actual numbers and as a percent of total
    diagnosed mortalities, is expected as wolves continue their
    colonization of areas with more human developments and a
    denser network of roads and vehicle traffic.”). Additionally,
    the Service looked to Minnesota depredation data from 2007
    and 2008 (the time when the Western Great Lakes wolf
    population was temporarily delisted under the now-vacated
    2007 Rule), and found that the rates of depredation deaths did
    not change materially from before the wolves were delisted. 
    Id. at 81,704
    (noting that 133 Minnesota wolves were killed in
    2007 and 143 wolves in 2008, compared to 134 in 2005 and
    122 in 2006). The Service further found that the Western Great
    Lakes wolf population continued to grow despite the increase
    in depredation deaths in 2007 and 2008 in Wisconsin and
    Michigan. See 
    id. at 81,708
    (noting that the Wisconsin wolf
    population increased 12% between 2008 and 2009); 
    id. at 81,712
    (noting that the Michigan wolf population grew 11%
    between 2008 and 2009).
    The Service also addressed the problem of illegal killings.
    The Service candidly acknowledged the limited data available
    since such killings “generally occur in remote locations and the
    evidence is easily concealed[.]” Final Rule, 76 Fed. Reg. at
    81,698. Nevertheless, the data that the Service was able to
    collect indicated that the number and proportion of wolves
    killed illegally in Wisconsin declined while the gray wolf was
    delisted under the later-vacated 2007 Rule. See 
    id. at 81,696
    (showing 17 of 72 wolves found dead in 2006 had been killed
    illegally and 20 of 72 in 2009, compared to 10 of 90 in 2007
    43
    and 14 of 94 in 2008); 
    id. (illegal killings
    were 67% of all
    mortality in 2006, 62% in 2006, and 44% in 2010 compared to
    19% in 2007 and 23% in 2008). Other than that, the Service
    concluded that it was “not possible at this time to determine if
    human-caused mortality (apart from mortalities from
    depredation control) has significantly changed over the nearly
    35-year period that the gray wolf has been listed as threatened
    or endangered.” 
    Id. at 81,700.
    What ultimately proved most relevant to the Service was
    that, over all of the studied time periods, “all sources of wolf
    mortality, including legal (for example, depredation control)
    and illegal human-caused mortality, have not been of sufficient
    magnitude to stop the continuing growth of the wolf
    population[.]” 2011 Rule, 76 Fed. Reg. at 81,700; see also 
    id. (“Despite human-caused
    mortalities of wolves in Minnesota,
    Wisconsin, and Michigan, these wolf populations have
    continued to increase in both numbers and range.”).
    In short, the record supports the Service’s conclusion that
    disease- and human-caused mortality have not materially
    threatened the expansion of the gray wolf population in the
    Western Great Lakes region, and thus the Service reasonably
    concluded that those factors do not counsel against delisting.
    See Rossello ex rel. Rossello v. Astrue, 
    529 F.3d 1181
    , 1185
    (D.C. Cir. 2008) (“Substantial-evidence review is highly
    deferential to the agency fact-finder, requiring only ‘such
    relevant evidence as a reasonable mind might accept as
    adequate to support a conclusion.’”) (quoting Pierce v.
    Underwood, 
    487 U.S. 552
    , 565 (1988)).
    The Service further noted that state plans in Minnesota,
    Michigan, and Wisconsin would monitor wolf disease and
    mortality, providing an important backstop should new threats
    emerge. See 2011 Rule, 76 Fed. Reg. at 81,697. The veterinary
    44
    pathologist peer reviewer agreed that the state plans would
    adequately monitor and protect against new disease threats.
    Finally, the data evidenced that mortality rates due to disease
    and depredation would not be affected in any significant
    measure by delisting. 
    Id. at 81,700–81,701.
    The Service’s analysis also answers the Humane Society’s
    concern about the combined impact of disease and human-
    caused mortality. The simple reality is that both disease- and
    human-caused deaths have been simultaneously afflicting the
    wolves, and yet the population has continued to grow
    nonetheless.
    B
    The district court also held that the 2011 Rule is arbitrary
    and capricious because the Service failed to adequately address
    what it described as an “unregulated killing zone” in Minnesota
    and the lack of state regulatory plans to monitor and protect the
    wolves in six of the Western Great Lakes States. Humane
    
    Society, 76 F. Supp. 3d at 134
    –136. We again conclude that
    the Service’s decision was reasonable and grounded in
    substantial evidence.
    1
    With respect to the Minnesota state plan, what the district
    court labeled an “unregulated killing zone” refers to
    depredation controls in one particular area of the State. The
    Minnesota Plan divides the State into two zones. Within Zone
    A, an area covering Northeastern Minnesota and the core of the
    wolves’ territory, wolves can only be legally killed in defense
    of a human life, in situations of “immediate threat” to the life
    of a guard animal or domestic pet, or immediately after a
    verified loss of livestock, domestic animals, or pets. See MINN.
    STAT. § 97B.645, subdivs. 3, 5, 6. An “immediate threat” is
    45
    defined as a wolf stalking, attacking, or killing. See 
    id. § 97B.645,
    subdiv. 12(c). Within this zone, a “control area”
    can be opened immediately following the government’s
    verification of the loss of livestock, domestic animals, or pets.
    See 
    id. § 97B.671,
    subdiv. 4(c). However, the control area can
    only be opened for sixty days, and it must be within a one-mile
    radius of the site of the loss. See 
    id. § 97B.671,
    subdiv. 4(c),
    (d). Trained and certified predator controllers will be paid
    $150 for each wolf they kill within the control area. In
    addition, owners of livestock and domesticated animals within
    Zone A may shoot or destroy a wolf that poses “an immediate
    threat” to such animals “on property owned, leased or occupied
    by the owner” of the animal. 
    Id. § 97B.645,
    subdiv. 5.
    Likewise, in Zone B, a controlled killing area can be
    opened following a verified loss of livestock, domestic
    animals, or pets. See MINN. STAT. § 97B.671, subdiv. 4(b).
    The control area may be opened for 30 to 214 days, depending
    on the time of year, and may be opened anytime within five
    years of a verified loss. See id.; J.A. 439. Only trained and
    certified predator controllers, operating with the permission of
    the landowners within the control area, may legally take a wolf.
    See MINN. STAT. § 97B.671, subdivs. 1, 4(b). In addition, a
    person may shoot a wolf on land owned, leased, or managed by
    that person at any time to protect that person’s livestock,
    domestic animals, or pets, regardless of whether the wolf is an
    immediate threat. See 
    id. § 97B.645,
    subdiv. 8.
    Given those limitations, we disagree with the district
    court’s and the Humane Society’s characterization of Zone B
    as an “unregulated killing zone.” See Humane Society, 76 F.
    Supp. 3d at 134; Humane Society’s Br. 77–78. Minnesota only
    permits the killing of a wolf in Zone B by a limited class of
    persons, and only after there has been some threat to livestock
    or domestic animals. And at the time the 2011 Rule issued,
    46
    killing a wolf outside of the plan’s specific authorizations or
    without a license was a gross misdemeanor. See MINN. STAT.
    § 97A.331, subdiv. 7 (2011), repealed by Act of May 3, 2012,
    ch. 277, art. 1, § 91, 2012 Minn. Laws 1169.
    In other words, the Minnesota Plan does not authorize the
    unregulated killing of any wolf at any time by any person. It
    provides for regulated killing. To be sure, killings are allowed
    at higher numbers than the Humane Society wants. That does
    not make the Service’s decision unreasoned or arbitrary and
    capricious, however. To the contrary, the Service adequately
    explained why Minnesota’s new depredation scheme was
    unlikely to threaten the wolves’ survival. In coming to that
    conclusion, the Service did not ignore that the wolves residing
    in Zone B “could be subject to substantial reduction in
    numbers, and at the extreme, wolves could be eliminated from
    Zone B.” 2011 Rule, 76 Fed. Reg. at 81,704. Rather, the
    Service explained that “there is no way to reasonably evaluate
    in advance the extent to which residents of Zone B will use this
    new authority, nor how vulnerable Zone B wolves will be” in
    actuality. 
    Id. What the
    Service did know and found relevant
    to its decision was that statistical data from 2007 to 2008, when
    the Minnesota gray wolves were not federally listed, revealed
    that only six wolves were shot in Zone B during that time
    period, and in 2009 only one additional wolf was taken. 
    Id. Overall, the
    total number of wolves taken through depredation
    controls from 2007 to 2008 (133 in 2007, 143 in 2008) was
    comparable to the number that had been taken under a prior
    federal regulation. See 
    id. (under pre-2007
    federal regulation,
    105 wolves were killed in 2004, 134 in 2005, and 122 in 2006).
    Looking to data from 2007 to 2008 to predict the
    consequences of delisting was entirely reasonable because
    there was an absence of federal regulation and a presence of
    state depredation authorizations nearly identical to the regime
    47
    that would operate after delisting. In addition, the Service is
    obligated to continue monitoring the gray wolf for five years
    following any successful delisting and to make “prompt use”
    of its emergency powers “to prevent a significant risk to the
    well being of any such recovered species.” 16 U.S.C.
    § 1533(g)(2). Concerned entities also remain free to petition
    the Service to relist the gray wolf should it be threatened once
    more. 
    Id. § 1533(b)(3).
    For those reasons, the Service’s
    consideration of the Minnesota plan in its delisting decision
    was not arbitrary or capricious and was reasonably grounded in
    substantial evidence.
    2
    The Service’s decision to delist notwithstanding the lack
    of state plans in North and South Dakota, Illinois, Iowa, Ohio,
    and Indiana also did not rise to the level of arbitrary-and-
    capricious decisionmaking, given the near non-existence of
    gray wolves within those jurisdictions. The boundaries of the
    Western Great Lakes segment includes only portions, at times
    very small ones, of those six States, and few if any gray wolves
    are found there. See, e.g., 2011 Rule, 76 Fed. Reg. at 81,671
    (map of Great Lakes segment area); 
    id. at 81,700
    (sixteen total
    reports of wolf sightings or deaths in North Dakota from 1999
    to 2003); 
    id. at 81,713
    (no gray wolves found in Ohio and
    Indiana). Scientific literature cited by the Service indicates that
    the only gray wolves found in North and South Dakota are
    primarily loners, not packs or mates with pups. 
    Id. at 81,679;
    see also 
    id. at 81,700
    (detailing every report of wolves in North
    and South Dakota). Since 1993, there have been only five
    verified wolf deaths from depredation and eight total deaths
    from all causes of mortality in North and South Dakota. 
    Id. at 81,713
    (depredation deaths); 
    id. at 81,700
    (total deaths). Both
    Ohio and Indiana list the gray wolf as “extirpated” from their
    States. 
    Id. at 81,713
    . Indiana, Illinois, Ohio, and Iowa, “do not
    48
    contain suitable habitat [for gray wolves] or currently
    established packs[.]” 
    Id. In addition,
    the absence of formal state wolf plans does not
    mean that the few wolves in those States lack legal protection.
    The Service explained that, in North Dakota and Iowa, there is
    no open season on wolves because they are “furbearers.” 2011
    Rule, 76 Fed. Reg. at 81,713. Illinois includes gray wolves on
    its state endangered species list, making it illegal to possess or
    kill a wolf in the state. Id.; see 520 ILL. COMP. STAT. 10/3
    (detailing state law protections for endangered species). In
    South Dakota, wolves are not listed as a game animal open for
    hunting. 2011 Rule, 76 Fed. Reg. at 81,713. In short, in North
    Dakota, South Dakota, Iowa, and Illinois, gray wolves are
    protected from indiscriminate hunting. Only in Indiana and
    Ohio, where wolves no longer exist, are there no formal
    protections in place. 
    Id. But it
    is not arbitrary or capricious to
    overlook a State’s failure to protect an animal that does not
    exist within its borders.
    Further, for all six of the States with no wolf plans, the
    Service reasonably concluded that the deaths of any wolves
    that might enter those States would be so minimal as to pose no
    threat to the segment’s survival. 2011 Rule, 76 Fed. Reg. at
    81,713. For example, the deaths since 1993 of a total of eight
    wolves in North and South Dakota is quite unlikely to pose a
    survival threat to the several thousand wolves protected within
    Minnesota’s borders. Similarly, the death of a lone wolf that
    might roam into Indiana or Ohio would be highly unlikely to
    affect the health or sustainability of the Western Great Lakes
    segment.
    The district court faulted the Service’s decision on the
    ground that the limited number of wolves “does not foreclose
    the possibility of an increased presence there[.]” Humane
    49
    
    Society, 76 F. Supp. 3d at 134
    . True. But the Endangered
    Species Act tasks the Service with determining whether the
    species is endangered or threatened, not whether the species
    could reach still higher population levels if given more
    protection. Challenges to expanding a species’ territory do not
    by themselves undermine survival in existing territory.
    We accordingly hold that the absence of conservation
    plans for the gray wolves in North Dakota, South Dakota,
    Illinois, Iowa, Ohio, and Indiana does not render the Service’s
    decision to delist the Western Great Lakes gray wolves
    arbitrary and capricious on this record.
    C
    Finally, the Humane Society challenges the 2011 Rule as
    violating the Service’s statutory obligation to ground the
    delisting decision in the best available science, 16 U.S.C.
    § 1533(b)(1)(A). The Humane Society argues first that science
    does not support the 2011 Rule because the Service admits that
    the Minnesota gray wolf is not a separate species of wolf under
    the Endangered Species Act. The Humane Society argues
    secondly that the 2011 Rule responded to political pressure, not
    science. Neither argument succeeds.
    1
    With respect to the status of the gray wolf in Minnesota,
    the Service initially proposed classifying it as a separate
    species (the “eastern wolf” or Canis lycaon). See Proposed
    Rule to Revise the List of Endangered and Threatened Wildlife
    for the Gray Wolf (Canis lupus), 76 Fed. Reg. 26,086, 20,086
    (May 5, 2011) (“Proposed 2011 Rule”). But in the final 2011
    Rule, the Service admitted that “neither a scientific consensus
    nor the majority opinion of researchers on the taxonomy of
    wolves” supported designating the wolves in Minnesota as a
    50
    distinct species. 2011 Rule, 76 Fed. Reg. at 81,669. In the
    Humane Society’s view, once the Service determined that the
    Minnesota gray wolf was not a separate species, the Service
    should have withdrawn the rule, rather than promulgate a final
    rule “without knowing the species that it is both listing and
    delisting.” Humane Society’s Br. 61 (emphasis in original).
    But the Service did know that the Minnesota wolves that
    it added to the Western Great Lakes segment were part of the
    gray wolf species. See 2011 Rule, 76 Fed. Reg. at 81,669 (“The
    wolves that occupy the [Western Great Lakes segment] have
    long been accepted as gray wolves, C. lupus[.]”). In that
    respect then, the Service’s treatment of the wolves in
    Minnesota as part of the gray wolf species aligns with the best
    science available, which was inconclusive as to whether the
    Minnesota wolves were a separate species or just a subspecies
    of the gray wolf. See 
    id. at 81,668–81,669
    (discussing the
    scientific literature on wolf taxonomy).
    In any event, the Service’s recognition of the Western
    Great Lakes segment did not depend on a finding that the
    Minnesota wolves were a separate species. From the outset,
    the Service proposed recognizing a distinct population segment
    in the region. See Proposed 2011 Rule, 76 Fed. Reg. at 26,094
    (“Within this rule we are proposing changes to the listing for
    C. lupus and are initiating a status review for C. lycaon. These
    two actions combined will address all wolves in the [Western
    Great Lakes] region.”); 
    id. (“Our proposed
    action here is to
    establish the existence of a [Western Great Lakes] distinct
    population segment of C. lupus and to determine that the
    [segment] is neither endangered nor threatened, despite its
    proximity to a closely related species, C. lycaon—a species
    whose status we will evaluate for possible protection under the
    Act in the near future.”). When the science did not support
    according a distinct species status to wolves in Minnesota, the
    51
    Service followed where the science led by treating the
    Minnesota wolves as non-distinct and grouping them with all
    of the other wolves in the Western Great Lakes region.
    2
    The record likewise does not support the Humane
    Society’s charge that the delisting decision was driven by
    politics rather than science. The Society’s argument relies
    primarily on a single letter from United States Senator Amy
    Klobuchar of Minnesota supporting delisting, which prompted
    several emails within the Service discussing the Senator’s
    letter.     But a single communication from an elected
    representative conveying the views of constituents could not by
    itself politically poison an agency’s decisionmaking. That is
    especially true when, as here, the Society does not point to any
    science that the Service ignored, misused, or manipulated, or
    to any material switch in the Service’s position after receiving
    the letter.
    On December 7, 2010, Senator Klobuchar sent a letter to
    Ken Salazar, the then-Secretary of the Interior, “urg[ing]” the
    Service “to expedite the delisting of the gray wolf in the Great
    Lakes” and communicating her intent to introduce legislation
    “to help speed-up this process.” J.A. 771. Assistant Secretary
    Thomas Strickland’s response to Senator Klobuchar referenced
    the 2009 Rule delisting the gray wolf in that region, which at
    that time had been withdrawn due to litigation, and further
    informed the Senator that the Service intended to publish a new
    proposed rule delisting the wolf by April 2011. Senator
    Klobuchar then made a public announcement about the
    Service’s forthcoming proposed rule.
    Such a commonplace senatorial inquiry, standing alone,
    cannot taint an agency decision that is otherwise adequately
    reasoned and grounded in the factual record. And certainly not
    52
    here where the Service’s threefold effort to delist the region’s
    gray wolves preceded the Senator’s letter by multiple years.
    See 2003 Rule, 68 Fed. Reg. at 15,857 (final rule delisting gray
    wolves); 2007 Rule, 72 Fed. Reg. at 6,101 (same); 2009 Rule,
    74 Fed. Reg. at 15,120 (same). In addition, the Service had
    received multiple petitions to delist the Western Great Lakes
    wolves and had decided that those petitions presented
    substantial evidence meriting delisting several months before
    Senator Klobuchar’s letter. See 90-Day Finding on Petitions to
    Delist the Gray Wolf in Minnesota, Wisconsin, Michigan and
    the Western Great Lakes, 75 Fed. Reg. 55,730, 55,735 (Sept.
    14, 2010).
    The Humane Society’s reliance on Save Our Springs v.
    Babbitt, 
    27 F. Supp. 2d 739
    (W.D. Tex. 1997), actually proves
    the opposite. Unlike the case at hand, the Service in Save Our
    Springs succumbed to political pressure and withdrew a
    proposed listing of salamanders even though it had earlier
    stated that the salamander was the “top priority in the region
    for listing.” 
    Id. at 745.
    The level of political pressure,
    moreover, bears no resemblance to the single letter in this case.
    In Save Our Springs, the pressure came through a letter from
    the Governor of Texas, emails from employees worrying that
    listing was a “hot” issue and noting “intense opposition” to the
    proposal from all levels of Texas government, and “inferences
    that political lobbyists for the development community worked
    with political appointees.” 
    Id. The record
    here reflects no such
    concerted pressure, no manipulation or disregard of material
    evidence, and no change in the Service’s course of action
    before and after the single communication. 10
    10
    Likewise, Western Watersheds Project v. Fish & Wildlife
    Service, 
    535 F. Supp. 2d 1173
    (D. Idaho 2007), involved a “well-
    documented history” of a Deputy Assistant Secretary “intervening in
    the listing process,” “editing scientific conclusions” and
    53
    We accordingly find no merit to the charge of improper
    political influence in this case.
    V
    A common remedy when we find a rule is invalid is to
    vacate. See Sugar Cane Growers Co-op. of Fla. v. Veneman,
    
    289 F.3d 89
    , 97 (D.C. Cir. 2002) (“Normally when an Agency
    * * * clearly violates the APA we would vacate its action[.]”).
    But we may remand without vacatur depending upon “the
    seriousness of the order’s deficiencies (and thus the extent of
    doubt whether the agency chose correctly) and the disruptive
    consequences of [vacating the Rule,] an interim change that
    may itself be changed.” 
    Id. at 98
    (citation omitted); Allina
    Health Servs. v. Sebelius, 
    746 F.3d 1102
    , 1110 (D.C. Cir.
    2014); see also United States Sugar Corp. v. EPA, 
    844 F.3d 268
    , 270 (D.C. Cir. 2016) (per curiam) (“Although remand
    without vacatur may in some circumstances invite prejudicial
    agency delay, in other circumstances vacatur itself carries
    more-harmful consequences. We have therefore frequently
    remanded without vacating when a rule’s defects are curable
    and where vacatur would at least temporarily defeat * * * the
    enhanced protection of the [rule].”) (first alteration in original;
    internal quotation marks and citations omitted).
    In this case, the agency’s analysis (i) wholly failed to
    address the effect on the remnant population of carving out the
    Western Great Lakes segment, and in doing so (ii) misapplied
    the Service’s own discreteness and significance tests, and also
    (iii) turned its back on the implications of historical range loss.
    Those are major shortcomings that go to the heart of the
    “intimidating [Service] staffers,” 
    id. at 1175;
    see also 
    id. at 1188
    (The Deputy Assistant Secretary “had extensive involvement in the
    sage-grouse listing decision, used her intimidation tactics in this
    case, and altered the ‘best science’ to fit a not-warranted decision.”).
    54
    Service’s delisting decision. Given the serious and pervading
    role those deficiencies played in the agency’s decisionmaking,
    there is substantial “doubt whether the [Service] chose
    correctly” in promulgating the 2011 Rule, Sugar Cane
    
    Growers, 289 F.3d at 98
    (citation omitted). That makes vacatur
    appropriate. See 
    id. at 97–98;
    Fox Television Stations, Inc. v.
    FCC, 
    280 F.3d 1027
    , 1049, 1052–1053 (D.C. Cir. 2002).
    In addition, vacatur would not trigger disruptive
    consequences. The agency has failed repeatedly over the last
    sixteen years to make a delisting decision that complies with
    the APA, and it has not shown that vacatur here would be any
    more disruptive than it was on the Service’s last three failed
    occasions. With respect to protecting domestic animals in the
    interim, federal regulations already permit depredation control
    in Minnesota, which is where most of the gray wolves in the
    Western Great Lakes segment live. See 50 C.F.R. § 17.40(d).
    Because of the “seriousness of the [Rule’s] deficiencies”
    and the absence of materially “disruptive consequences,” we
    affirm the judgment of the district court vacating the Service’s
    2011 Rule.
    So ordered.