Excerpts: The parties make much of FWS's footnote interpreting the phrase "interbreeds when mature" in the ESA's definition of "species." In the footnote, FWS takes the position that the phrase means that "a DPS must consist of members of the same species or subspecies," as defined by the "biological species" concept. See Remand Mem. 1 n.1. Intervenors assert that the phrase means that members of a DPS must be "capable of interbreeding." ... And AFRC asserts that the phrase means that members of a DPS must actually interbreed. ... The Court need not now decide which (if any) of these interpretations is correct, however, because under any interpretation of the phrase "interbreeds when mature," FWS has rationally concluded that central California murrelets actually interbreed when mature with other murrelets in the tri-state DPS, albeit at low levels. The judge said he needed "to clarify the following statement in [his] March 30, 2013 memorandum opinion: 'If the genetic distinctiveness of the two populations comprising the tri-state DPS means that they do not interbreed when mature, then FWS's significance determination cannot be upheld.' See Am. Forest Res. Council, 2013 WL 1289724, at *11" (Opinion here) In remanding FWS's significance determination here, the Court's intent was not to define once and for all the meaning of the arguably "ambiguous" phrase "interbreeds when mature." Because the phrase appears in the ESA's text, the Court concluded that interbreeding when mature, however defined, is a statutory condition for classification as a DPS. The Court did not hold that FWS must make an explicit finding that members of a DPS interbreed when mature in every case. But because in this case AFRC had asserted that two genetically distinct populations cannot interbreed when mature, and because FWS had not spoken on this disputed issue of biology, the Court remanded the significance determination to obtain the agency's considered view. See Am. Forest Res. Council, 2013 WL 1289724, at *11. The Court intended only to have FWS determine whether central California murrelets and other murrelets in the DPS "interbreed when mature," not to define the meaning of that phrase for the agency. Accordingly, a perhaps better formulation of the Court's prior statement is that FWS's significance determination would be called into question if the genetic distinctiveness of the two murrelet populations in the tristate DPS means that they do not, or cannot, "interbreed when mature," however that phrase is defined. In light of its determination that central California murrelets interbreed when mature with other murrelets in the DPS, FWS reaffirmed its January 2010 significance determination. Its reasoning is not difficult to discern. Factors that may bear on a DPS's biological and ecological significance include: "[p]ersistence of the discrete population segment in an ecological setting unusual or unique for the taxon," "[e]vidence that loss of the discrete population segment would result in a significant gap in the range of a taxon," and "[e]vidence that the discrete population segment differs markedly from other populations of the species in its genetic characteristics." 61 Fed. Reg. at 4725. FWS initially found that loss of the tri-state DPS would result in a significant gap in the murrelet's range because the tri-state area accounts for about 18 percent of the murrelet's coastal distribution, spans 17 degrees of latitude, is located at the southern periphery of the murrelet's range, and contains an ecologically distinct forest system, the coastal redwoods. See 75 Fed. Reg. at 3430. The agency also found that loss of the DPS would result in the loss of "unique genetic characteristics" that are significant to the taxon. [B]ecause FWS has concluded that central California murrelets are properly included in the DPS, its previously stated rationales remain valid and, in the Court's view, are adequate to withstand arbitrary and capricious review. The Court will not second guess FWS's determination that a hypothetical loss of 18 percent of the murrelet's coastal distribution and 17 degrees of latitude would be significant, as that is the kind of judgment that is best left to agency expertise. Re: vacatur and remand FWS has not asked for vacatur, and neither AFRC nor intervenors argue that any remand should be with vacatur, so the Court does not consider vacatur an option at this time. The Court therefore weighs the equities of remanding without vacatur against those of deciding the merits and possibly vacating the challenged rule. Weighing the equities here, the Court will grant FWS's motion for voluntary remand without vacatur. As previously stated, avoiding further litigation of this matter will conserve the resources of the Court and the parties, as well as taxpayer dollars. A substantial part of the relief requested – a remand of the murrelet critical habitat designation to FWS – will be granted whether FWS's motion is granted now or AFRC prevails on the merits later. Although FWS hints that briefing on the merits would be "solely" about vacatur, the Court has little confidence that the merits litigation would be so confined. AFRC does not limit its request to briefing the issue of vacatur, and intervenors do not concede that AFRC would prevail on its critical habitat claims. See AFRC VR Opp'n 2, 19 (request to "present dispositive summary judgment motions on the critical habitat claims"); Intervenors' VR Resp. 4-5 (stating that merits determination would require "review of the not-yet-filed administrative record and fully-developed legal argument"). And even if the appropriateness of vacatur were the only issue before the Court, determining the seriousness of the critical habitat rule's deficiencies would necessitate the expenditure of considerable time and resources. Finally, the Court concludes that, although AFRC has raised some legitimate objections, it will not be unduly prejudiced by remand without vacatur. As a practical matter, since briefing on the merits has not yet transpired, it would be many months before a decision on the merits could be rendered by the Court. The critical habitat designation would remain in force during that time regardless of the Court's decision today, and so the additional amount of time that AFRC will be subject to the rule as a result of voluntary remand is actually less than three years. Also, the murrelet critical habitat designation is a longstanding rule that may be justified by FWS on remand. The real possibility that the rule's deficiencies can be addressed on remand, and hence that the rule would not be vacated in any case, decreases the expected benefit to AFRC and the public of going forward with this litigation now. That possibility also increases the likelihood that a three-year interim vacatur will be unduly disruptive. And AFRC has not convinced the Court that the ill-defined prejudice to its timber interests outweighs the certain benefits to be gained by avoiding further litigation. Hence, the Court will remand the murrelet critical habitat designation to FWS and order FWS to submit a new proposed critical habitat designation by not later than September 30, 2015, and a new final critical habitat designation by not later than September 30, 2016.