Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for 22 Species in the Commonwealth of the Northern Mariana Islands and the Territory of Guam
Federal RegisterMar 24, 2026
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
[Docket No. FWS-R1-ES-2024-0194; FXES1111090FEDR-267-FF09E21000]
RIN 1018-BI17
Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for 22 Species in the Commonwealth of the Northern Mariana Islands and the Territory of Guam
AGENCY:
Fish and Wildlife Service, Interior.
ACTION:
Proposed rule.
SUMMARY:
We, the U.S. Fish and Wildlife Service (Service), propose to designate critical habitat for 9 animal species and 13 plant species from the Mariana Islands (the U.S. Territory of Guam and the Commonwealth of Northern Mariana Islands) under the Endangered Species Act (Act). In total across both the Territory and Commonwealth, approximately 59,886 acres (24,235 hectares) on the islands of Aguiguan, Alamagan, Asunción, Guam (including the island of Cocos), Pagan, Rota, Saipan, Sarigan, and Tinian fall within the boundaries of the proposed critical habitat designation. We also announce the availability of an economic analysis of the proposed designation of critical habitat for these species.
DATES:
We will accept comments received or postmarked on or before June 22, 2026. Comments submitted electronically using the Federal eRulemaking Portal (see
ADDRESSES
, below) must be received by 11:59 p.m. eastern time on the closing date.
We must receive requests for a public hearing, in writing, at the address shown in
FOR FURTHER INFORMATION CONTACT
by May 8, 2026.
ADDRESSES:
Comment Submission:
You may submit comments by one of the following methods:
(1)
Electronically:
Go to the Federal eRulemaking Portal:
https://www.regulations.gov.
In the Search box, enter FWS-R1-ES-2024-0194, which is the docket number for this rulemaking. Then, click on the Search button. On the resulting page, in the panel on the left side of the screen, under the Document Type heading, check the Proposed Rule box to locate this document. You may submit a comment by clicking on “Comment.”
(2)
By hard copy:
Submit by U.S. mail to: Public Comments Processing, Attn: FWS-R1-ES-2024-0194, U.S. Fish and Wildlife Service, MS: PRB/3W, 5275 Leesburg Pike, Falls Church, VA 22041-3803.
We request that you send comments only by the methods described above. We will post all comments on
https://www.regulations.gov.
This generally means that we will post any personal information you provide us (see Information Requested, below, for more information).
Availability of supporting materials:
Supporting materials, such as the economic analysis, are available on the Service's website at
https://www.fws.gov/project/critical-habitat-mariana-islands,
at
https://www.regulations.gov
at Docket No. FWS-R1-ES-2024-0194, or both. If we finalize the critical habitat designation, we will make the coordinates or plot points or both from which the maps are generated available at
https://www.regulations.gov
at Docket No. FWS-R1-ES-2024-0194 and on the Service's website at
https://www.fws.gov/project/critical-habitat-mariana-islands.
FOR FURTHER INFORMATION CONTACT:
Earl W. Campbell, Project Leader, U.S. Fish and Wildlife Service, Pacific Islands Fish and Wildlife Office, 300 Ala Moana Boulevard, Room 3-122, Honolulu, HI 96850; by telephone 808-792-9400. Individuals in the United States who are deaf, deafblind, hard of hearing, or have a speech disability may dial 711 (TTY, TDD, or TeleBraille) to access telecommunications relay services. Individuals outside the United States should use the relay services offered within their country to make international calls to the point-of-contact in the United States. Please see Docket No. FWS-R1-ES-2024-0194 on
https://www.regulations.gov
for a document that summarizes this proposed rule.
SUPPLEMENTARY INFORMATION:
Executive Summary
Why we need to publish a rule.
Under the Act (16 U.S.C. 1531
et seq.
), when we determine that any species is an endangered or threatened species, we are required to designate critical habitat, to the maximum extent prudent and determinable. Designations and revisions of critical habitat can be completed only by issuing a rule through the Administrative Procedure Act rulemaking process (5 U.S.C. 551
et seq.
). We are proposing a designation of critical habitat for 22 Mariana Islands species, totaling 59,886 acres (ac) (24,235 hectares (ha)). We have also identified lands that meet the definition of critical habitat for another Mariana Island species, an endangered plant species,
Solanum guamense
(birenghenas hålom tåno', biringhenas halumtånu', birengenas hålomtåno'), but that does not have a proposed critical habitat designation in this proposed rule because the identified lands are exempt from being designated as critical habitat in accordance with section 4(a)(3)(B)(i) of the Act.
For the sake of brevity, throughout this document we collectively refer to these species as the “Mariana Islands species, also including/noting reference to
Solanum guamense,
when applicable.” Sixteen of the Mariana Islands species were previously listed as endangered species (80 FR 59424; October 1, 2015): seven plants—
Eugenia bryanii
(no common name),
Hedyotis megalantha
(pao de'do', påode'du', pao doodu),
Heritiera longipetiolata
(ufa hålumtåno', ufa halumtånu', ufa hålomtåno'),
Phyllanthus saffordii
(maigo' lålo'),
Psychotria malaspinae
(åplohkåteng palao'an, åpplok hatting palao'an, aplokkating palåo'an),
Solanum guamense,
and
Tinospora homosepala
(no common name); and nine animals—the Pacific sheath-tailed bat (Mariana subspecies,
Emballonura semicaudata rotensis;
paye'ye', payesyes, fanihen gånas, paye'yi', payesyis, fanihin gånas, paischeey), Slevin's skink (
Emoia slevini;
Marianas Emoia, Mariana skink, guåli'ek hålomtåno', gholuuf, guali'ik halumtånu'), Mariana eight-spot butterfly (
Hypolimnas octocula marianensis;
ababang, ababbang, libweibwogh), Mariana wandering butterfly (
Vagrans egistina;
ababang, ababbang, libweibwogh), Rota blue damselfly (
Ischnura luta;
dulalas Luta), fragile tree snail (
Samoana fragilis;
dengdeng, dengding, akaleha', denden), Guam tree snail (
Partula radiolata;
dengdeng, dengding, akaleha', denden), humped tree snail (
Partula gibba;
dengdeng, dengding, akaleha', denden), and Langford's tree snail (
Partula langfordi;
dengdeng, dengding, akaleha', denden). Seven of the 23 Mariana Islands species, all plants, were previously listed as threatened species (80 FR 59424; October 1, 2015):
Bulbophyllum guamense
(wild onion, siboyas hålomtåno', siboyas halumtånu', siboyan hålomtåno'),
Dendrobium guamense
(no common name),
Cycas micronesica
(fadang, faadang),
Maesa walkeri
(no common name),
Nervilia jacksoniae
(no common name),
Tabernaemontana rotensis
(no common name), and
Tuberolabium guamense
(no common name).
Additionally, we note that a 5-year status review for
Tuberolabium
guamense
was completed on August 4, 2025, recommending we remove the species from the Federal List of Endangered and Threatened Plants. Recommendations in 5-year reviews are not final agency decisions and we have not initiated work on a proposed delisting rule as of publication of this proposed critical habitat designation; however, if we finalize a delisting rule for
Tuberolabium guamense,
the conservation measures provided by the Act (
e.g.,
through sections 7 and 9) would no longer apply to
Tuberolabium guamense,
and we would also remove critical habitat for the species.
What this document does.
We propose the designation of critical habitat for 22 wildlife and plant species that occur on islands within the Territory of Guam and the Commonwealth of the Northern Mariana Islands.
The basis for our action.
Under section 4(a)(3) of the Act, if we determine that a species is an endangered or threatened species we must, to the maximum extent prudent and determinable, designate critical habitat.
Section 3(5)(A) of the Act defines critical habitat as (i) the specific areas within the geographical area occupied by the species, at the time it is listed, on which are found those physical or biological features (I) essential to the conservation of the species and (II) which may require special management considerations or protections; and (ii) specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination by the Secretary that such areas are essential for the conservation of the species. Section 4(b)(2) of the Act states that the Secretary must make the designation on the basis of the best scientific and commercial data available and after taking into consideration the economic impact, the impact on national security, and any other relevant impacts of specifying any particular area as critical habitat.
Acronyms and Abbreviations Used in This Proposed Rule
For the convenience of the reader, listed below are some of the acronyms and abbreviations used in this proposed rule:
Act = Endangered Species Act
AFB = Air Force Base
CBA = Conservation Benefit Agreement
CFR = Code of Federal Regulations
CNMI = Commonwealth of the Northern Mariana Islands
CNMI BECQ = CNMI Bureau of Environmental and Coastal Quality
CNMI BTS Program = CNMI Division of Fish and Wildlife Brown Tree Snake Interdiction Program
CNMI DEQ = CNMI Division of Environmental Quality
CNMI DFW = CNMI Division of Fish and Wildlife
CNMI DPL = CNMI Department of Public Lands
CNMI FDoA = CNMI Forestry Division of Agriculture—Department of Lands and Natural Resources
CNMI OPD = CNMI Office of the Governor, Office of Planning and Development
CNMI SWARS = CNMI's Statewide Assessment and Resource Strategy Council
DHS = Department of Homeland Security
DoD = Department of Defense
DoN = U.S. Department of Navy
GDAWR = Guam Division of Aquatic and Wildlife Resources
GDPR = Guam Department of Parks and Recreation
GPEPP = Guam Plant Extinction Prevention Program
IEM = Incremental Effects Memorandum
INRMP = Integrated Natural Resources Management Plan
JRM = Joint Region Marianas
MOA = Memorandum of Agreement
MCB = Marine Corps Base
NHP = National Historical Park
NMFS = National Marine Fisheries Service
NPS = U.S. National Park Service
NWR = National Wildlife Refuge
PBF = Physical or Biological Feature
RFA = Regulatory Flexibility Act
Service = U.S. Fish and Wildlife Service
SSP = Socio-Economic Pathway
USDA WS = U.S. Department of Agriculture Wildlife Services
USGS = U.S. Geological Survey
UOG = University of Guam
Information Requested
We intend that any final action resulting from this proposed rule will be based on the best scientific and commercial data available and be as accurate and as effective as possible. Therefore, we request comments or information from other governmental agencies, the indigenous community, the scientific community, industry, or any other interested parties concerning this proposed rule. We particularly seek comments concerning:
(1) Specific information on:
(a) The amount and distribution of habitat for the Mariana Islands species;
(b) Any additional areas occurring within the range of the Mariana Islands species that should be included in the designation because they (i) are occupied at the time of listing and contain the physical or biological features that are essential to the conservation of the species and that may require special management considerations or protection, or (ii) are unoccupied at the time of listing and are essential for the conservation of the species;
(c) Modifications that may be necessary for different types of projects to ensure protection of physical or biological features for a given species;
(d) Special management considerations or protection that may be needed in critical habitat areas we are proposing, including managing for the potential effects of climate change; and
(e) For the Pacific sheath-tailed bat, whether areas not occupied at the time of listing qualify as habitat for the species and are essential for the conservation of the species.
(2) Land use designations and current or planned activities in the subject areas and their possible impacts on proposed critical habitat.
(3) Information on any specific areas that we have identified as “uncategorized” land ownership.
(4) Any probable economic, national security, or other relevant impacts of designating any area that may be included in the final designation, and the related benefits of including or excluding specific areas.
(5) Information on the extent to which the description of probable economic impacts in the economic analysis is a reasonable estimate of the likely economic impacts and any additional information regarding probable economic impacts that we should consider, particularly the impact on land values of private lands included in the critical habitat designation.
(6) Information on how project modifications may impact affected areas—especially considering the remoteness of some islands and the role of Federal funding in local economies.
(7) Whether any specific areas we are proposing for critical habitat designation should be considered for exclusion under section 4(b)(2) of the Act, and whether the benefits of potentially excluding any specific area outweigh the benefits of including that area under section 4(b)(2) of the Act, in particular for those that we are considering for exclusion, including the Memorandum of Agreement (MOA) for the Mariana Crow (åga or
Corvus kubaryi
) Conservation Area (includes a 684-ac (277-ha) portion of the I'Chenchon Bird Sanctuary), Rota Local Law No. 9-1 for the Sabana Protected Area (Commonwealth of Northern Mariana Islands (CNMI) 1994, entire), and the Talakhaya Integrated Watershed Management Plan (CNMI DEQ 2012, entire). If you think we should exclude any additional areas, such as the areas under consideration within the draft Guam Habitat Conservation Plan that is in an early stage of development, or the Anao, Bolanos, and Cotal Conservation
Areas, please provide information supporting a benefit of exclusion.
(8) Whether we could improve or modify our approach to designating critical habitat in any way to provide for greater public participation and understanding, or to better accommodate public concerns and comments.
Please include sufficient information with your submission (such as scientific journal articles or other publications) to allow us to verify any scientific or commercial information you include.
Please note that submissions merely stating support for, or opposition to, the action under consideration without providing supporting information, although noted, do not provide substantial information necessary to support a determination. Section 4(b)(2) of the Act directs that the Secretary shall designate critical habitat on the basis of the best scientific data available.
You may submit your comments and materials concerning this proposed rule by one of the methods listed in
ADDRESSES
. We request that you send comments only by the methods described in
ADDRESSES
.
If you submit information via
https://www.regulations.gov,
your entire submission—including any personal identifying information—will be posted on the website. If your submission is made via a hardcopy that includes personal identifying information, you may request at the top of your document that we withhold this information from public review. However, we cannot guarantee that we will be able to do so. We will post all hardcopy submissions on
https://www.regulations.gov.
Comments and materials we receive, as well as supporting documentation we used in preparing this proposed rule, will be available for public inspection on
https://www.regulations.gov.
Our final designation may differ from this proposal because we will consider all comments we receive during the comment period as well as any information that may become available after this proposal. Based on the new information we receive (and, if relevant, any comments on that new information), our final designation may not include all areas proposed, may include additional areas that meet the definition of critical habitat, or may exclude areas if we find the benefits of exclusion outweigh the benefits of inclusion and exclusion will not result in the extinction of the species. In our final rule, we will clearly explain our rationale and the basis for our final decision, including why we made changes, if any, that differ from this proposal.
Public Hearings
Section 4(b)(5) of the Act provides for a public hearing on this proposal, if requested. Requests must be received by the date specified in
DATES
. Such requests must be sent to the address shown in
FOR FURTHER INFORMATION CONTACT
. We will schedule a public hearing on this proposal, if requested, and announce the date, time, and place of the hearing, as well as how to obtain reasonable accommodations, in the
Federal Register
and local newspapers at least 15 days before the hearing. We may hold the public hearing in person or virtually via webinar. We will announce any public hearing on our website, in addition to the
Federal Register
. The use of virtual public hearings is consistent with our regulations at 50 CFR 424.16(c)(3).
Previous Federal Actions
It is our intent to discuss in this document only those topics directly relevant to the proposed designation of critical habitat for the 22 Mariana Islands species. For more information on the taxonomy, biology, and ecology of the Mariana Islands species addressed in this proposed rule, refer to the final listing rule that published in the
Federal Register
on October 1, 2015 (80 FR 59424), available online at
https://www.regulations.gov
(at Docket No. FWS-R1-ES-2014-0038).
On July 20, 2021, the Center for Biological Diversity (Plaintiff) filed a complaint (Case No. 21-CV-00017) alleging that the Service violated the Act by failing to comply with the statutory deadline for designating critical habitat for 23 Mariana Islands species listed on October 1, 2015 (80 FR 59424). On April 18, 2022, the parties entered into a stipulated settlement agreement, which was subsequently approved by the Court, whereby the Service agreed to submit to the
Federal Register
proposed critical habitat designations for the species in the complaint on or before June 26, 2025. In compliance with the settlement agreement, this document constitutes the proposed critical habitat designation for 22 of the species where the Service has jurisdiction to designate critical habitat. For one of the species (
i.e., Solanum guamense
), the areas that meet the definition of critical habitat are exempt under section 4(a)(3)(B)(i) of the Act (see Exemptions, below). Therefore, there is no critical habitat designation proposed for
Solanum guamense.
Peer Review
In accordance with our joint policy on peer review published in the
Federal Register
on July 1, 1994 (59 FR 34270), and our August 22, 2016, memorandum updating and clarifying the role of peer review in listing and recovery actions under the Act, we are soliciting independent scientific review of this proposed critical habitat designation to ensure that this proposal is based on scientifically sound data and analysis. We have invited peer reviewers to comment on our specific assumptions, methodology, and science used in this proposed rule, and we will consider any comments received, as appropriate, before a final agency determination.
The Mariana Islands
The Mariana Islands are a longitudinally arranged archipelago consisting of 15 main islands and various smaller islets located in western Micronesia between latitudes 21° and 13° N and longitudes 144° and 146° E. The primarily volcanic northern islands include Farallon de Medinilla, Anatahan, Sarigan, Guguan, Alamagan, Pagan, Agrihan, Asuncion, Maug, and Uracas, while the limestone and volcanic southern islands include Guam, Rota, Aguiguan, Tinian, and Saipan. The northern islands of Anatahan, Guguan, Alamagan, Asuncion, Pagan, and Uracas are still volcanically active. Only the southern islands of Guam (including Cocos Island), Rota, Tinian, and Saipan are regularly inhabited by humans; all the other Mariana Islands are considered uninhabited, although some (
e.g.,
Aguiguan, Pagan) may be visited on occasion. Please see the proposed listing rule (79 FR 59364 at 59367-59377, October 1, 2014) for more background information on the Mariana Islands' geography, vegetation, hydrology, climate, biogeography, historical and current human impacts, political division, island-specific descriptions, and details regarding the ecosystems upon which the species addressed in this proposed rulemaking action depend.
Common Name Changes
Following publication of the final listing rule (80 FR 59424; October 1, 2015), we have identified new common names for some of the Mariana Islands species. Table 1 is a list of the species' Latin names, and updated common names, including corrected versions (the column “Common name(s) updated” includes all currently known common names). Common names are not regulatory and may be updated without a rulemaking action; these names are included here for transparency. Diacritical marks are included in table 1 but not in the proposed regulations.
Table 1—23 Mariana Islands Species: Latin Names and New Common Names
[
ChG
= Chamorro name in Guam's spelling,
ChCNMI
= Chamorro name in CNMI's spelling,
Ca
= Carolinian name, NCN = no common name]
Latin name
Common name(s) updated
Emballonura semicaudata rotensis
Pacific sheath-tailed bat, paye'ye'
ChG
, payesyes
ChG
, fanihen gånas
ChG
, paye'yi'
ChCNMI
, payesyis
ChCNMI
,
fanihin gånas
ChCNMI
, paischeey
Ca
.
Emoia slevini
Slevin's skink, Marianas Emoia, Mariana skink, guåli'ek hålomtåno'
ChG
, gholuuf
Ca
, guali'ik halumtånu'
ChCNMI
.
Samoana fragilis
fragile tree snail, dengdeng
ChG
, dengding
ChCNMI
,
akaleha'
ChG>
&
ChCNMI
, denden
Ca
.
Partula radiolata
Guam tree snail, dengdeng
ChG
, dengding
ChCNMI
,
akaleha'
ChG>
&
ChCNMI
, denden
Ca
.
Partula gibba
humped tree snail, dengdeng
ChG
, dengding
ChCNMI
,
akaleha'
ChG>
&
ChCNMI
, denden
Ca
.
Partula langfordi
Langford's tree snail, dengdeng
ChG
, dengding
ChCNMI
,
akaleha'
ChG &
ChCNMI
, denden
Ca
.
Hypolimnas octocula marianensis
Mariana eight-spot butterfly, ababang
ChG
,
ababbang
ChCNMI
, libweibwogh
Ca
.
Vagrans egistina
Mariana wandering butterfly, ababang
ChG
,
ababbang
ChCNMI
, libweibwogh
Ca
.
Ischnura luta
Rota blue damselfly,
dulalas Luta
ChG, ChCNMI, and Ca
.
Bulbophyllum guamense
wild onion, siboyas hålomtåno'
ChG
,
siboyas halumtånu'
ChCNMI
, siboyan hålomtåno'
Ca
.
Cycas micronesica
fadang
ChG &
ChCNMI
, faadang
Ca
.
Dendrobium guamense
NCN.
Eugenia bryanii
NCN.
Hedyotis megalantha
pao de'do'
ChG
, påode'du'
ChCNMI
, pao doodu
Ca
.
Heritiera longipetiolata
ufa hålomtåno'
ChG
, ufa halumtånu'
ChCNMI
,
ufa hålomtåno'
Ca
.
Maesa walkeri
NCN.
Nervilia jacksoniae
NCN.
Phyllanthus saffordii
maigo' lålo'
ChG
.
Psychotria malaspinae
aplohkåteng palao'an
ChG
, åpplok hatting palao'an
ChG
aplokkating palåo'an
ChCNMI
.
Solanum guamense
birenghenas hålomtåno'
ChG
,
biringhenas halumtånu'
ChCNMI
, birengenas hålomtåno'
Ca
.
Tabernaemontana rotensis
NCN.
Tinospora homosepala
NCN.
Tuberolabium guamense
NCN.
Background
Regulatory Framework
Section 4(a)(3) of the Act requires that, to the maximum extent prudent and determinable, we designate a species' critical habitat concurrently with listing the species. Critical habitat is defined in section 3(5)(A) of the Act as:
(1) The specific areas within the geographical area occupied by the species, at the time it is listed in accordance with the Act, on which are found those physical or biological features
(a) Essential to the conservation of the species, and
(b) Which may require special management considerations or protection; and
(2) Specific areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.
Our regulations at 50 CFR 424.02 define the geographical area occupied by the species as an area that may generally be delineated around species' occurrences, as determined by the Secretary (
i.e.,
range). Such areas may include those areas used throughout all or part of the species' life cycle, even if not used on a regular basis (
e.g.,
migratory corridors, seasonal habitats, and habitats used periodically, but not solely by vagrant individuals).
Conservation, as defined under section 3(3) of the Act, means to use and the use of all methods and procedures that are necessary to bring an endangered or threatened species to the point at which the measures provided pursuant to the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, and transplantation, and, in the extraordinary case where population pressures within a given ecosystem cannot be otherwise relieved, may include regulated taking.
Critical habitat receives protection under section 7 of the Act through the requirement that each Federal action agency ensure, in consultation with the Service, that any action they authorize, fund, or carry out is not likely to result in the destruction or adverse modification of designated critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation also does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by non-Federal landowners. Rather, designation requires that, where a landowner requests Federal agency funding or authorization for an action that may affect an area designated as critical habitat, the Federal agency consult with the Service under section 7(a)(2) of the Act. If the action may affect the listed species itself (such as for occupied critical habitat), the Federal agency would have already been required to consult with the Service
even absent the designation because of the requirement to ensure that the action is not likely to jeopardize the continued existence of the species. Even if the Service were to conclude after consultation that the proposed activity is likely to result in destruction or adverse modification of the critical habitat, the Federal action agency and the landowner are not required to abandon the proposed activity, or to restore or recover the species; instead, they must implement “reasonable and prudent alternatives” to avoid destruction or adverse modification of critical habitat.
Under the first prong of the Act's definition of critical habitat, areas within the geographical area occupied by the species at the time it was listed are included in a critical habitat designation if they contain physical or biological features (1) which are essential to the conservation of the species and (2) which may require special management considerations or protection. For these areas, critical habitat designations identify, to the extent known using the best scientific data available, those physical or biological features that are essential to the conservation of the species (such as space, food, cover, and protected habitat).
Under the second prong of the Act's definition of critical habitat, we can designate critical habitat in areas outside the geographical area occupied by the species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.
Section 4(b)(2) of the Act requires that we designate critical habitat on the basis of the best scientific data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the
Federal Register
on July 1, 1994 (59 FR 34271)), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106-554; H.R. 5658)), and our associated Information Quality Guidelines provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.
When we are determining which areas should be designated as critical habitat, our primary source of information is generally the information compiled in the Species Status Assessment report and information developed during the listing process for the species. A Species Status Assessment was not available for this proposed rule; however, additional information sources are used that may include any generalized conservation strategy, criteria, or outline that may have been developed for the species; the recovery plan for the species; articles in peer-reviewed journals; conservation plans developed by States and counties; scientific status surveys and studies; biological assessments; other unpublished materials; or experts' opinions or personal knowledge.
Habitat is dynamic, and species may move from one area to another over time. We recognize that critical habitat designated at a particular point in time may not include all of the habitat areas that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be needed for recovery of the species. Areas that are important to the conservation of the species, both inside and outside the critical habitat designation, will continue to be subject to: (1) Conservation actions implemented under section 7(a)(1) of the Act; (2) regulatory protections afforded by the requirement in section 7(a)(2) of the Act for Federal agencies to ensure their actions are not likely to jeopardize the continued existence of any endangered or threatened species; and (3) the prohibitions found in section 9 of the Act
for the endangered species
and the 4(d) rule
for the threatened species.
Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. These protections and conservation tools will continue to contribute to recovery of the species. Similarly, critical habitat designations made on the basis of the best scientific data available at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if new information available at the time of those planning efforts calls for a different outcome.
Physical or Biological Features Essential to the Conservation of the Species
In accordance with section 3(5)(A)(i) of the Act and regulations at 50 CFR 424.12(b), in determining which areas we will designate as critical habitat from within the geographical area occupied by the species at the time of listing, we consider the physical or biological features that are essential to the conservation of the species, and which may require special management considerations or protection. The regulations at 50 CFR 424.02 define “physical or biological features essential to the conservation of the species” as the features that occur in specific areas and that are essential to support the life-history needs of the species, including, but not limited to, water characteristics, soil type, geological features, sites, prey, vegetation, symbiotic species, or other features. A feature may be a single habitat characteristic or a more complex combination of habitat characteristics. Features may include habitat characteristics that support ephemeral or dynamic habitat conditions. Features may also be expressed in terms relating to principles of conservation biology, such as patch size, distribution distances, and connectivity. For example, physical features essential to the conservation of the species might include gravel of a particular size required for spawning, alkaline soil for seed germination, protective cover for migration, or susceptibility to flooding or fire that maintains necessary early-successional habitat characteristics. Biological features might include prey species, forage grasses, specific kinds or ages of trees for roosting or nesting, symbiotic fungi, or absence of a particular level of nonnative species consistent with conservation needs of the listed species. The features may also be combinations of habitat characteristics and may encompass the relationship between characteristics or the necessary amount of a characteristic essential to support the life history of the species.
In considering whether features are essential to the conservation of the species, we may consider an appropriate quality, quantity, and spatial and temporal arrangement of habitat characteristics in the context of the life-history needs, condition, and status of the species. These characteristics include, but are not limited to, space for individual and population growth and for normal behavior; food, water, air, light, minerals, or other nutritional or physiological requirements; cover or shelter; sites for breeding, reproduction, or rearing (or development) of offspring; and habitats that are protected from disturbance.
Rationales and Summary Lists of Physical or Biological Features for Each Species or Grouping of Species
We derive the following specific physical or biological features (PBFs)
essential to the conservation of the Mariana Islands species from studies of the species' habitat, ecology, and life history as described below. Additional information can be found in the 5-year reviews (Service 2020a-2020s, entire; Service 2021, entire; Service 2024a-b, entire), species reports (Service 2020t-2020ao, entire; 2023b-x, entire), and the recovery plan (Service 2023a, entire); other sources of information as cited, available on
https://www.regulations.gov
under Docket No. FWS-R1-ES-2024-0194). We have determined that the following PBFs are essential to the conservation of the Mariana Islands species:
Mammals
(1) Pacific Sheath-Tailed Bat (Subspecies,
Emballonura semicaudata rotensis
) PBFs
a.
Pacific sheath-tailed bat PBF 1:
Limestone caves, lava tubes, overhanging cliffs, and crevasses for roosting.
b.
Pacific sheath-tailed bat PBF 2:
Intact, contiguous forests near and surrounding suitable roosting sites.
c.
Pacific sheath-tailed bat PBF 3:
Prey insects such as ants, bees, wasps (Hymenoptera), moths (Lepidoptera), and beetles (Coleoptera) and vegetation to support them.
The last known surviving population of Pacific sheath-tailed bat, subspecies
rotensis
(hereafter referred to as “Pacific sheath-tailed bat” unless referring to another subspecies), roosts in a few caves on Aguiguan (Lemke 1986, entire; Service 2020b, p. 5; Service 2023h, pp. 3, 29), although the species formerly occupied Guam, Rota, and Tinian (Wiles et al. 2011, pp. 299-300). The species spends more than half its life in roost caves, which are near forests with well-developed tree canopy close to cave entrances; the forests maintain relatively stable cave microclimates, provide food, and allow flight passage (Esselstyn et al. 2004, p. 307; Gorresen et al. 2009, pp. 337-339; O'Shea and Valdez 2009, pp. 77-78; Service 2020u, p. 13; Service 2023h, p. 12). Pacific sheath-tailed bats depend on caves because they roost as lone adults next to lone young on ceilings or upper walls in caves, overhangs, lava tubes, or crevasses where limestone karst is present (Wiles et al. 2011, p. 303; Service 2020b, pp. 4, 6-8; Service 2020u, p. 5; Service 2023h, pp. 11-12). On Aguiguan, the bats are primarily detected in native forests, occasionally in nonnative forest, and are not detected in non-forested habitats (Esselstyn et al. 2004, pp. 306-307), showing a clear association of the bat with forests on Aguiguan; non-forest habitats are largely avoided by the species (Esselstyn et al. 2004, p. 307).
Although the species appears to prefer relatively large caves (Wiles et al. 2011, pp. 299, 302), on Aguiguan, the species is observed in multiple cave shapes and structures, including the following: small (less than 49 ft (15 m) long and 538 square feet (ft
2
) (50 square meters (m
2
)) in floor area), with low rock overhangs, narrow vertical crevices, various cavities at the base of cliffs or under large boulders; medium (538 ft
2
to 1,076 ft
2
(50 to 100 m
2
) in floor area), with wider rooms; and large (over 1,076 ft
2
(100 m
2
) in floor area), with ceiling heights reaching 16 to 98 ft (5 to 30 m) (Wiles and Brooke 2009, pp. 432-433; Wiles et al. 2011, p. 301; Service 2023h, p. 14). It is possible that the species may use even smaller caves. For example, on Palau where the closely related Pacific sheath-tailed bat, subspecies
palauensis
(also insectivorous) is known to occur, approximately 150 individuals of this subspecies were flushed from a cave-like formation on a forested hill that was even smaller, at 16 to 32 ft (5 to 10 m) long with a 6.5 ft (2 m) diameter opening (possibly a World War II tunnel) (Wiles et al. 1997, p. 221), while another colony, with several hundred bats and a few Mariana swiftlets (yåyaguak;
Aerodramus bartschi
), was found in a cave 32 ft (10 m) wide and 26 ft (8 m) tall (Wiles et al. 1997, p. 221). Thermal characteristics of Aguiguan cave interiors vary little; temperature highs range 79 to 86 °F (26 to 30 °C), relative humidity ranges 74 to 96 percent, and there is little air movement (O'Shea and Valdez 2009, pp. 77-78; Service 2020u, p. 9; Service 2023h, p. 13); however, thermal characteristics of caves on Aguiguan do not limit use by this species, and it seems unlikely that humidity variations among caves is a limiting factor (Wiles et al. 2011, p. 305).
Forests are the most important foraging habitat for the Pacific sheath-tailed bat (Esselstyn et al. 2004, p. 307). The species is insectivorous, foraging on small insects such as ants, bees, wasps, moths, and beetles supported by forested habitat (O'Shea and Valdez 2009, pp. 63-65; Valdez et al. 2011, pp. 301-307; Service 2023h, p. 10). On Aguiguan, the bats were regularly seen in the forest understory to within 3 ft (1 m) of the ground, with some activity at tree-top level (Esselstyn et al. 2004, p. 306). Canopy heights on Aguiguan are 23-49 ft (7-15 m) tall, which are shorter than forested areas outside the Mariana Islands partially from frequent intense tropical cyclones (Wiles et al. 2011, pp. 300, 306; Service 2023h, p. 12). Tropical cyclones damage and remove trees, leading to a lower canopy level from defoliation, branch breakage, and tree uprooting from high winds and heavy rain. Average canopy heights were less than 4.25 ft (1.3 m) in 2016 surveys, indicating canopy cover was absent at most survey points (CNMI DFW 2016, p. 42). Suitable caves need to be in or near mature, well-structured, native or nonnative forests to provide attainable food sources because this species forages almost exclusively in native and nonnative forests near their roosts, but especially native forests, and avoids non-forested habitats (Esselstyn et al. 2004, p. 307; Palmeirim et al. 2005, pp. 7-8; Gorresen et al. 2009, pp. 336-339; O'Shea and Valdez 2009, p. 44; Wiles et al. 2009, p. 10; Wiles et al. 2011, p. 307; Service 2020u, pp. 6, 11).
On the islands (archipelago) of Palau, which is approximately 113,280 ac (45,843 ha) in size and where the closely related
palauensis
subspecies of Pacific sheath-tailed bat exists, at least one of these individuals has been documented to fly at least 3.1 mi (5 km) from known roosts (Wiles et al. 1997, p. 221). For comparison, on the small Aguiguan Island (1,750 ac (4,324 ha) or 2.74 mi
2
in size), we anticipate the bats on Aguiguan rely heavily on the forests adjacent to roosting habitat, depending on prey availability. Suitable foraging habitat is mature, well-structured forests with a high and dense canopy near suitable roosting sites. This is necessary to maintain a stable or growing bat population (Kalko 1995, pp. 262-265; Esselstyn et al. 2004, p. 307; Palmeirim et al. 2005, pp. 3-5, 7-8; Gorresen et al. 2009, pp. 336-339; Valdez et al. 2011, pp. 306-307; Marques et al. 2016, pp. 481-484; Service 2023a, p. 25).
Previous disturbance by human occupation and warfare during World War II and ongoing disturbance of roosting caves by human and feral goats contribute to the decline of this species (Wiles et al. 2011, p. 306; Service 2020u, p. 10) by affecting mating, rearing young, social interactions, protection from inclement weather, and causing elevated energetic costs, physiological stress, and increased risk of depredation (Palmeirim et al. 2005, p. 7; Kunz and Lumsden 2003, pp. 4, 43, 66; Service 2020u, p. 10). Historical warfare and ongoing disturbances have contributed to roost abandonment for the Pacific sheath-tailed bat. The degree and frequency of disturbance resulting in cave abandonment by the species is not well understood; however, inhabitation of roosting caves near and/or within suitable foraging habitat may occur again after physical disturbances have been alleviated. Feral goats take shelter in caves, disrupt colonies of the
federally endangered Mariana swiftlet, and likely disturb the Pacific sheath-tailed bat (Wiles and Worthington 2002, p. 17; Cruz et al. 2008, p. 243; Scanlon 2015, in litt., entire; Service 2023h, pp. 14-15). Suitable caves are found unoccupied by this species and were occupied by goats (GDAWR 1995, p. 95).
Reptiles
(2) Slevin's skink (
Emoia slevini
) PBFs
a.
Slevin's skink PBF 1:
Forests such as native limestone forests, volcanic forests, mixed-nonnative forests,
Casuarina equisetifolia
(gågu, gågo, weighu, beach sheoak, or common ironwood) and
Cocos nucifera
(niyok, coconut) dominant forests.
b.
Slevin's skink PBF 2:
Forest understory and leaf litter and debris.
c.
Slevin's skink PBF 3:
Invertebrate prey and vegetation to support them.
Slevin's skink is the only lizard endemic to the Mariana Islands and has had a 99 percent decline in its distribution. It is known to occur only on Alamagan, Asuncion, Cocos Island (which is part of Guam), and Sarigan, and possibly Pagan, but it is thought to be extinct or undetected on Guam, Rota, Tinian, and Aguiguan (Service 2023j, p. 3). Threats to this species include loss and degradation of habitat due to impacts from feral ungulates, nonnative plants, and development; predation by invasive species (
e.g.,
rats, brown tree snake); and competition from nonnative lizards (Service 2023j, pp. 3, 16-38).
The skinks are often seen on forest floors containing leaf litter and tree debris, and observed on trees, within low hollows of tree trunks, under logs, within palm fronds, and near abandoned buildings, but rarely observed in open or sunlit areas (Brown and Falanruw 1972, p. 110; Rodda et al. 1991, p. 205; CNMI DFW 2000, in litt., pp. 21-26; GDAWR 2006, p. 107; Vogt 2007, pp. 5-1 to 5-2; Lardner 2013, in litt., p. 4). Recorded forest types inhabited by Slevin's skink include ravine, native, mixed-native, mixed secondary, and forests of
Casuarina equisetifolia
and
Cocos nucifera
(Brown and Falanruw 1972, p. 110; McCoid et al. 1995, p. 72; CNMI DFW 2005, p. 175; Vogt 2007, in litt., pp. 5-1 to 5-2). The species also likely uses forests with habitat complexity, typical of the Mariana Islands, comprised of limestone or volcanic substrates and native tree canopy species, such as
Elaeocarpus joga, Pisonia grandis, Hernandia labyrinthica, Hernandia sonora, Ficus prolixa, Macaranga thompsonii, Pandanus
spp., and
Intsia bijuga
for limestone forests; and
Pisonia grandis, Hernandia sonora, Barringtonia asiatica, Pandanus tectorius,
and
Terminalia catappa
for volcanic forests (Service 2023j, p. 15).
Females carry eggs internally, birth live young and require understory of leaf litter and tree debris to hide from predators and to stalk prey (insectivorous) (Harrington et al. 2020, p. 14). Like all insectivorous skinks, individuals require a sufficient abundance of insects and small invertebrates to complete their development and life cycle, including mating and breeding (Harrington et al. 2020, p. 15; Service 2023j, p. 15). Males of many other skink species are aggressively territorial, and we expect the Slevin's skink to also be territorial (Service 2023j, p. 15). The territory area necessary for Slevin's skink is unknown; however, wherever suitable habitat remains within their historic range, we expect they may be present, just undetected, because they were undetected on Guam's Cocos Island for almost two decades (Cocos is approximately 95 ac, or 38 ha) (Service 2020c, p. 4; Service 2023j, p. 16).
Snails
(3) Tree Snails: Fragile tree snail (
Samoana fragilis
), Guam tree snail (
Partula radiolata
), humped tree snail (
Partula gibba
), and Langford's tree snail (
Partula langfordi
) PBFs
a.
Tree snail PBF 1:
Contiguous closed-canopy limestone, volcanic, riverine, riparian, ravine, or secondary/mixed forests, or backstrand beach vegetation, providing relatively stable climatic conditions such as shade, moisture, high humidity, and low air movement.
b.
Tree snail PBF 2:
Dense mid-canopy vegetation such as large leaves, branches, vines, or other structures.
c.
Tree snail PBF 3:
Understory such as ground cover composed of short herbs, shrubs, ferns, and small trees.
d.
Tree snail PBF 4:
Food sources such as dead and decaying plant material, leaf litter, and tree debris.
The tree snails require sufficiently dense forests that are cool, shaded, and have high humidity and stable environmental factors including temperature, relative humidity, and light to prevent excessive moisture loss to their bodies, and to provide conditions conducive to growth of fungi and microalgae (Crampton 1925, p. 14; Cowie 1992, p. 175; Service 2020w, p. 6; Service 2023b, p. 12; Service 2023c, p. 3; Service 2023d, pp. 3, 6; Service 2023e, p. 10). Excessive light and unstable temperatures and humidity have detrimental impacts on juvenile survival (Gouveia 2011, pp. 68, 76-78; Service 2023d, p. 12; Service 2023e, p. 10; Service 2023c, p. 10; Service 2023b, p. 12). The tree snails require forest understory containing live and decaying leaves and branches, suggesting a diet of fungus or microalgae (Service 2023d, p. 12; Service 2023e, pp. 10-11; Service 2023c, p. 10; Service 2023b, p. 12). Threats to tree snails include loss and degradation of habitat due to impacts from development, wildfire, invasive plants, typhoons, and climate change (
e.g.,
increasing temperatures, changes in precipitation patterns); and predation from invasive animals (Service 2023a, pp. 17-24).
The tree snails are most likely found on broad-leafed plants in places with canopy and ground cover (Fiedler 2019, pp. 10-11). The species are commonly observed in forests with a mid-canopy of less than or equal to 13 ft (4 m), ground cover of short herbaceous plants and small shrubs (Fiedler 2019, p. 10), and contiguous suitable habitat (Service 2020t, p. 9; Service 2020w, p. 7; Service 2020v, p. 14). Partulid snails can be found high in trees, depending on the tree and location. Tree snails were observed on leaves higher than 26 ft (8 m) from the ground (Fiedler 2019, p. 13). The snails are not known to have specific host plant requirements, except a preference for large leaves (to take refuge under), and they are found on the underside of leaves of a variety of native and nonnative vegetation. However, based on limited observational studies, population densities are lower on nonnative vegetation than those on native vegetation for the fragile tree snail on Guam and the humped tree snail on Sarigan, CNMI (CNMI DFW 2008, p. 8-4; Fiedler 2019, p. 7; Service 2020v, pp. 6, 12).
Observations of the tree snails on native vegetation most commonly occur on (but are not limited to)
Piper guahamense, Mammea odorata
(chopak, chopag), and
Merrilliodendron megacarpum
(no common name) (observed for humped tree snail);
Aglaia
spp. (observed for Langford's tree snail);
Alocasia macrorrhizos
(giant taro),
Artocarpus
spp.,
Cocos nucifera, Epipremnum aureum, Merrilliodendron megacarpum
(observed for Guam tree snail); and
Arterocarpus
spp. and
Merrilliodendron megacarpum
(observed for fragile tree snail) (Service 2023b, pp. 16-17; Service 2023c, p. 14; Service 2023d, pp. 11-12; Service 2023e, pp. 10, 15). The tree snails are also observed in backstrand beach vegetation—plant communities near or directly adjacent to the ocean, where the salinity is higher and the vegetation is more salt-tolerant and that may contain volcanic or limestone substrates (CNMI
DFW 2015a, pp. 4-6; Service 2023d, pp. 16-18).
The snails have both male and female reproductive organs and birth live young, but juvenile mortality rates are very high (Pearce-Kelly et al. 1995, p. 660; Service 2023d, p. 13; Service 2023e, pp. 11-12; Service 2023c, p. 11; Service 2023b, p. 13). Another primary threat to the snails is depredation by the nonnative New Guinea flatworm, a ground-dwelling flatworm that climbs wet trees and locates snails via scent (Sugiura and Yamaura 2009, pp. 739-741; Service 2020x, p. 3; Service 2023d, pp. 3, 14; Service 2023e, pp. 3, 12; Service 2023c, p. 3; Service 2023b, p. 14). Other predators include the nonnative rosy wolf snail (Hopper and Smith 1992, p. 82; Service 2023c, p. 12) and the nonnative, invasive yellow crazy ant (Service 2023d, p. 14; Service 2023e, p. 12; Service 2023b, p. 14). Habitat loss and degradation have contributed substantially to population declines of the tree snails (Service 2023d, p. 14; Service 2023e, p. 13; Service 2023c, p. 12; Service 2023b, p. 14).
Insects
(4) Mariana eight-spot butterfly
(Hypolimnas octocula marianensis)
PBFs
a.
Mariana eight-spot butterfly PBF 1:
Interconnected native, closed-canopy limestone forests.
b.
Mariana eight-spot butterfly PBF 2:
Larval host plants such as
Procris pedunculata
(no common name) or
Elatostema calcareum
(tapun ayuyu).
c.
Mariana eight-spot butterfly PBF 3:
Food resources from day-flowering plants or decaying organic matter (
e.g.,
rotten fruits or animals).
The Mariana eight-spot butterfly (Nymphalidae family) once occurred across a much larger range of habitat than its current distribution on Guam, likely formerly occupying Rota and Tinian (which lie between currently occupied Guam and formerly occupied Saipan), and host plants are present on all islands (Schreiner and Nafus 1996, p. 2; Moore 2013, p. 2; Rubinoff and Holland 2018, p. 221; Service 2023f, pp. 3, 26, 27). The butterfly historically occupied Guam and Saipan, and on Saipan it had a range of approximately 21,600 ac (8,741 ha) (70 percent of the island); however, 99 percent of the native forest ecosystem habitat on Saipan is gone (Service 2023m, p. 28) and the species not been detected during anecdotal surveys performed for purposes other than detecting this species (Schreiner and Nafus 1996, p. 10; Moore 2013, p. 2; Rubinoff and Holland 2018, pp. 218-220, 222; Service 2023f, p. 27). Additionally, it is important to note for this and other species that pollinators and birds are almost entirely absent from Guam due to depredation by the invasive brown tree snake; the lack of pollinators and seed dispersers inhibits the reproduction of plant communities that support these listed species (Egerer et al. 2018, p. 655; Service 2020ak, pp. 2, 14).
Mariana eight-spot butterflies occupy habitat in limestone forest over karst spires, boulders, and small cliffs where the host plants are protected from ungulate grazing (Schreiner and Nafus 1996, p. 1; Rubinoff and Holland 2018, p. 222). Known larval host plants include
Procris pedunculata
and
Elatostema calcareum
(vine-like forest herbs growing on rocky and karst substrate in native limestone forests) (Schreiner and Nafus 1996, p. 1; Service 2023f, pp. 12, 14). Adults rely on ephemeral food sources including rotting fruit and nectar from day-blooming flowers in limestone forests, and dead animals, mostly available after the wet season, when plants bloom and fruiting occurs (Service 2020z, p. 12; Service 2021, p. 5; Service 2023f, pp. 3, 12). Larvae need safety during pupation and abundant food resources to grow; caterpillars eat the native host plants (Schreiner and Nafus 1996, p. 1; Service 2023f, pp. 12, 14). Like all butterflies, Mariana eight-spot butterflies require sufficient host plant material to eat as caterpillars, a safe place to pupate, and abundant food resources as adults (Service 2023g, p. 14). The adults require close proximity to larval host plants; moreover, tropical butterflies, including nymphalid species (
i.e.,
brush-footed butterflies in the Nymphalidae family), are less likely to fly through open areas, so forest habitat connectivity between the specific Mariana eight-spot butterfly larval stage host plant sites is required (Rubinoff and Kawahara 2011, in litt., entire; Rubinoff 2013, in litt., p. 1; Rubinoff and Holland 2018, pp. 223, 224; Scriven et al. 2015, p. 420; Scriven et al. 2017, pp. 206, 212; Service 2023f, p. 15). Threats to this species include loss and degradation of habitat due to impacts from feral ungulates, nonnative plants, and herbivory by slugs; and predation from native and nonnative insects including ants and parasitic wasps (Service 2023f, pp. 3, 16-24).
(5) Mariana wandering butterfly
(Vagrans egistina)
PBFs
a.
Mariana wandering butterfly PBF 1:
Interconnected native limestone forest.
b.
Mariana wandering butterfly PBF 2:
Native limestone forest understory vegetation.
c.
Mariana wandering butterfly PBF 3:
Larval host plants, such as
Maytenus thompsonii
(luluhut).
d.
Mariana wandering butterfly PBF 4:
Food resources from day-flowering plants or decaying organic matter (
e.g.,
rotten fruits or animals).
The Mariana wandering butterfly is endemic to Guam and Rota and likely occurred across a much larger range of habitat than its current habitat distribution on Guam and Rota (Swezey 1942 p. 35; Schreiner and Nafus 1997, p. 36; Rubinoff and Holland 2018, p. 218; Service 2020f, pp. 5-6; Service 2023g, p. 3). The butterfly is in the Nymphalidae family and is one of seven nymphalid species found in the Mariana Islands, including the Mariana eight-spot butterfly, from which we infer much because so little is known of the Mariana wandering butterfly (Service 2023g, p. 3). The Mariana wandering butterfly likely relies on camouflage for protection, as the cryptic coloring of the bottom of the wings, visible when folded up, appear much duller and leaf-like in color and mimic the surrounding vegetation (Service 2023g, p. 10). The species is likely very difficult to detect and there have been no consistent survey efforts (Rubinoff 2024, pers. comm.). Threats to the species include habitat loss and degradation due to impacts from feral ungulates and nonnative plants, and predation from native and nonnative insects (
e.g.,
ants, parasitic wasps) (Service 2023g., pp. 3, 17-22).
Like most nymphalid butterflies, the adults use a long proboscis to feed on a variety of ephemeral food sources including nectar of day-blooming flowers, rotting fruit, and occasionally dead animals (Service 2023g, p. 12). The Mariana wandering butterfly is known to rear successfully on the native plant
Maytenus thompsonii,
a small shrub-like tree endemic to the Mariana Islands and found primarily in the understory of native limestone forests (Swezey 1942, p. 35; Service 2023g, pp. 11-12).
Maytenus thompsonii
can grow to heights over 13 ft (4 m), and thickets of the trees can grow impenetrably dense (Rubinoff and Holland 2018, pp. 222-223), potentially offering protection of eggs and larvae. Although the species typically occurs within limestone forests, it is not restricted to rugged karst terrain like the host plants of the related Mariana eight-spot butterfly (Rubinoff and Holland 2018, p. 221). Like all butterflies, Mariana wandering butterflies require sufficient host plant material to eat as caterpillars, a safe
place to pupate, and abundant food resources as adults (Service 2023g, p. 14). Like the Mariana eight-spot, the Mariana wandering butterfly likely requires high-density host plant distribution within interconnected native limestone forest (Service 2020ah, pp. 15, 17; Service 2020z, pp. 14-15; Service 2023g, p. 14); all remaining suitable limestone forest may be a species need (Service 2020ah, p. 17).
(6) Rota blue damselfly (
Ischnura luta
) PBFs
a.
Rota blue damselfly PBF 1:
Contiguous closed-canopy forest habitats surrounding streams and their tributaries with adequate cool, clean, clear, moving water.
b.
Rota blue damselfly PBF 2:
Riparian vegetation adjacent to streams and their tributaries.
c.
Rota blue damselfly PBF 3:
Small prey such as water fleas, larvae, or other small invertebrate or aquatic organisms.
The Rota blue damselfly is endemic to Rota where it inhabits a single confirmed stream system, the Okgok Stream, in the Talakhaya watershed (Polhemus et al. 2000, p. 8; Service 2020g, p. 3; Service 2023i, p. 3). Adult damselflies require large areas of high-quality forest habitat connected to streams because breeding pairs are territorial, they fly long ranges seeking prey before maturing and returning to their selected breeding sites, and they have strong breeding site fidelity and remain relatively close to the aquatic environment where they lived as naiads (larvae) (Finke 1992, p. 449; Polhemus and Asquith 1996, p. 7; Service 2020aa, p. 16; Service 2023i, p. 15). The forest habitat must have sufficient density and distribution to maintain shaded forest understory conditions along streams to keep stream temperatures cool and provide refuge, shelter, adequate area for breeding individuals to expand into, and habitat for prey (Service 2020aa, pp. 3, 19). Threats to this species include loss and degradation of habitat due to impacts from feral ungulates, wildfire, typhoons, nonnative plants, development, and extraction of water from the steam systems; and predation (
i.e.,
nonnative fish and amphibians) (Service 2020aa, pp. 4, 32-46).
The species requires streams and tributaries for breeding and sufficient stream flow for larvae (naiad) development (Service 2020aa, pp. 3, 19; Service 2023i, p. 14). A primary direct stressor to the damselfly is water withdrawal from the island's streams necessary for damselfly use (Service 2023i, p. 4). Female damselflies lay eggs by inserting them into small slits in aquatic vegetation below the water surface and by laying eggs on rocks, algal mats, moss, or vegetation either below or above the water line (Williams 1936, pp. 302-309; Guillermo-Ferreira and Del-Claro 2011, pp. 275, 278-279). The larval stage is aquatic and requires clean, oxygenated water with low silt concentrations because the larvae breathe underwater and eat small aquatic insects and invertebrates (Polhemus and Asquith 1996, p. 4; Service 2023i, p. 3). The species is generally intolerant of high temperatures, pollutants, hypoxic conditions, and silted water, factors long identified as indicators of poor water quality (Moore 1997, p. 10; Solimini et al. 1997, pp. 21, 30-31). Rota blue damselfly larvae eat small aquatic insects and other invertebrates, such as water fleas, mosquito larvae, and other small aquatic organisms (Polhemus and Asquith 1996, p. 4; Service 2020aa, p. 17). Adults eat small flying insects, such as midges and small flies (Polhemus and Asquith 1996, p. 7; Service 2020aa, p. 15).
Epiphytic Orchids
(7) Epiphytic orchids:
Bulbophyllum guamense, Dendrobium guamense,
and
Tuberolabium guamense
PBFs
a.
Epiphytic orchids PBF 1:
Native limestone or volcanic forests with native host vegetation such as trees and tall shrubs, including forests along clifflines, forest edges, mountainous slopes and secondary/mixed and native volcanic ravine forests providing suitable host vegetation.
b.
Epiphytic orchids PBF 2:
Pollinators such as flies, wasps, and bees, and native vegetation to support them.
Host trees for the orchids are not species specific, but
Bulbophyllum guamense
primarily grows on native vegetation and most individuals (greater than 76 percent) of
Dendrobium guamense
and
Tuberolabium guamense
are found on native vegetation associated with primary limestone and volcanic, and secondary/mixed forests (Service 2023k, p. 9; Service 2023m, pp. 12, 17; Service 2023x, p. 14). The orchids are also found on trees and tall shrubs in secondary limestone and volcanic substrate forests, high in the canopy, in ravine secondary forests, under the canopy along forest edges and clifflines, and on the slopes within intact native volcanic forest ecosystems or habitats (Stone 1970, pp. 27, 38, 155; Falanruw et al. 1989, pp. 6-9; Raulerson and Rinehart 1991, pp. 61, 73, 96; Mueller-Dombois and Fosberg 1998, pp. 218, 268; CNMI DFW 2015b, pp. 4-7; Service 2020ab, pp. 17-18, 29; Service 2020ad, pp. 4, 6-8; Service 2020an, pp. 9, 12; Service 2023m, pp. 11-13). Most of the native forest ecosystem for these species has been lost due to natural and anthropogenic disturbance, including invasive species, development, volcanic eruptions, typhoons, and fire (Willsey et al. 2019, pp. 2, 13-18, 28); Guam lost 83 percent, Rota lost 53 percent, Saipan lost 99 percent, Tinian lost 96 percent, Aguiguan lost 45 percent, and Agrihan lost 32 percent (Service 2023m, pp. 28-29).
These three epiphytic orchid species reproduce vegetatively and sexually, and require diverse populations with all age classes present (seeds, seedlings, juveniles, and adults), and must be distributed across sufficient quality forest habitat with high levels of habitat connectivity between populations (Service 2023k, p. 19; Service 2023m, p. 11 Service 2023x, p. 13). Reproduction requires moss or other debris on tree trunks or branches that the three orchid species can root into or cling to (Service 2023k, p. 16; Service 2023m, p. 9; Service 2023x, p. 10). Mother plants disperse seeds onto a host plant surface where they require microbial partners, such as mycorrhizal fungi, to germinate and grow to adults (Alghamdi 2019, p. 502; Service 2020h, p. 7; Service 2020l, p. 8; Service 2020ab, pp. 10, 17). Flies are the most likely pollinator for
Bulbophyllum guamense,
but the three orchid species may also be pollinated by wasps and bees (Borba et al. 1999, p. 205; Humeau et al. 2011, p. 591; Service 2023k, p. 18; Stpiczynska et al. 2018, p. 565). Seed dispersal likely occurs with wind and rain (Service 2023k, p. 17).
Invasive species are the primary driver of island extinctions and are a primary factor underlying the alteration and degradation of native plant communities and habitats in the Mariana Islands (Service 2023a, p. 12; Spatz et al. 2017, p. 1). Steady ongoing habitat degradation and loss occurs from the following sources: ungulates eat native vegetation, prevent native vegetation growth, spread invasive species, and cause severe erosion; rodents eat seeds and plants and affect regeneration; reptiles eat seed-dispersing birds; and invertebrates kill the plants or change the ecosystem that supports them (Service 2023a, pp. 21-22; Willsey et al. 2019, pp. 15-16). Small population abundance and distribution of these epiphytic orchid species increases their vulnerability to threats (Service 2023a, p. 17).
Bulbophyllum guamense
is endemic to Guam and Rota, growing on trunks and branches of tall trees and shrubs in native, secondary/mixed forests, and native volcanic ravine forests containing
exact amounts of moisture, light, and wind (the species derives moisture from the atmosphere and moisture and nutrients from host vegetation) (Service 2023k, pp. 3, 16). Historically, this species was likely widely distributed in the native forest habitat along the clifflines and mountainous slopes of the southern Mariana Islands of Guam and Rota (Service 2023k pp. 27, 32). Common host vegetation for the orchids includes
Hernandia labyrinthica, Elaeocarpus joga, Pisonia umbellifera
(birdlime tree or bird-catcher tree),
Artocarpus
spp.,
Persea americana
(avocado), and
Areca catechu
(betel nut) (Stone 1970, p. 158; CNMI DFW 2015b, pp. 2, 4-7; Service 2023k, p. 16).
Bulbophyllum guamense
are found along slopes at relatively high elevations in native limestone and secondary forest habitats, which appears to protect them from stochastic events (
e.g.,
hurricanes) (Service 2020ab, pp. 3, 6-7, 9, 29).
Dendrobium guamense
is endemic to Guam, Rota, Saipan, Tinian, Aguiguan, and Agrihan, growing predominately on native (93 percent) tree trunks and branches of trees in the top of the tree canopy (Service 2023m, pp. 3, 5, 12), but also terrestrially under the canopy where it is found along forest edges and clifflines (CNMI DFW 2015b, pp. 3-5).
Dendrobium guamense
are mostly (76 percent) found on native trees, such as (but not limited to)
Elaeocarpus joga, Glochidion marianum
(chosgô), and
Pandanus tectorius
(Service 2023m, p. 12).
Tuberolabium guamense
is endemic to forest ecosystems of Guam and Rota with limestone and volcanic substrata, growing in low sunlight, low in the tree canopy, on tree trunks or shrubs of primarily native species (Service 2023x, p. 3; Stone 1970, pp. 14, 18-24). Known host vegetation includes (but is not limited to)
Aglaia mariannensis
(mapunyao, mapuñao, fischil liyoos),
Eugenia reinwardtiana
(cedar bay cherry), and
Merrilliodendron megacarpum
(see Service 2023x, pp. 14, 16 for full list).
Tuberolabium guamense
has little apparent specificity for precipitation within the current ranges recorded on Guam and Rota; it occupies sites across gradients in space spanning large differences in rainfall, temperature, and elevation (Service 2023x, p. 17).
Forest Plants
Historically, forest plant communities in the Mariana Islands were described as a diverse ecosystem where 10 or more species grew side by side in approximately equal abundance; these communities were represented by a diverse group of families and species, and none were dominated by any single species or by small groups of species (Glassman 1948, p. 177). The forests were not matted with undergrowth except where trees were few, and the ground cover species were usually confined to the forests (Glassman 1948, p. 179). Less than 17 percent of native forests remain on Guam, less than 47 percent remain on Rota (Willsey et al. 2019, p. 4), and less than 2 percent of native coastal habitats remain on any island in the Mariana Islands (Service 2023a, p. 21). Invasive species are the primary driver of island extinctions and are a primary factor underlying the alteration and degradation of native plant communities and habitats in the Mariana Islands (Service 2023a, p. 12; Spatz et al. 2017, p. 1) and for all of the forest plants. And as stated above, it is important to note that pollinators and birds are almost entirely absent from Guam due to depredation by the invasive brown tree snake, which can severely inhibit a plant's ability to reproduce (pollinators) and distribute (seed dispersers) (Egerer et al. 2018, p. 655; Service 2020ak, pp. 2, 14). Overall, we know very little about these rare forest plants as surveys and reports are few; therefore, we relied on the best available scientific information to identify their essential PBFs.
Forests in the Mariana Islands are characterized by a closed canopy of broadleaf trees with an understory of younger trees, vines, epiphytic ferns, and orchids (Willsey et al. 2019, p. 3). Present day limestone forests are largely (but not limited to)
Hibiscus tiliaceus, Morinda citrifolia
(lada', noni, Indian mulberry),
Psychotria mariana
(åpplok hating, aplohkateng, aplu kati, gathemach, aploghating, åplokhating),
Aidia cochinchinensis
(sumak),
Aglaia mariannensis, Ficus prolixa, Melanolepis multiglandulosa
(ålom),
Pandanus tectorius,
and
Pipturus
spp. The undergrowth is sparse, except for young trees of the above species and vines such as (but not limited to)
Abrus
spp.,
Freycinetia
spp., and
Operculina
spp.
;
very common are
Asplenium nidus
(gålak, fedda', bird's nest fern) and
Phymatosorus scolopendria
(monarch fern, kåhlao) (Mueller-Dombois and Fosberg 1998, pp. 216-217; Harrington et al. 2012, entire).
Coastal strand forests comprise the following components: They contain sandy soils, coastal strand vegetation, mangroves, and bare sand, rock, and karst; are contained within near-shore areas that are bounded by the ocean on one side and have a less distinct inland border; are found only in older and larger southern islands (
i.e.,
Guam and Rota); and support a narrow plant community along the shore from loose sand just above the high tide line extending to increasingly less saline volcanic or limestone soil conditions inland (Fosberg 1960, pp. 15-17; Plentovich et al. 2020, p. 186; Service 2020ac, p. 9; Service 2023l, pp. 11-12). Present-day coastal strand vegetation in the Marianas includes (but is not limited to)
Barringtonia asiatica, Bikkia tetrandra, Cassytha filiformis, Casuarina equisetifolia, Cordia subcordata, Heliotropium foertherianum, Hernandia nymphaeifolia, Hibiscus tiliaceus, Ipomoea pes-caprae
(halaihai, goats foot morning glory, bayhops, beach morning glory, railroad vine),
Lepturus repens, Mammea odorata, Ochrosia mariannensis, Pandanus tectorius, Pemphis acidula, Scaevola taccada
(nanåsu, beach naupaka, beach cabbage), Sesuvium
portulacastrum, Sporobolus virginicus, Thespesia populnea, Thuarea involuta,
and
Vigna marina
(akankang manulasa, akangkang malolusa, nanea, beach pea) (Plentovich et al. 2020, p. 187).
(8) Cycas micronesica PBFs
a.
Cycas micronesica PBF 1:
Closed-canopy native limestone or volcanic forests with native vegetation such as (but not limited to)
Hibiscus tiliaceus, Morinda citrifolia, Psychotria mariana, Aidia
spp.,
Aglaia
spp.,
Ficus
spp.,
Melanolepis multiglandulosa, Pandanus
spp., and
Pipturus
spp.
b.
Cycas micronesica PBF 2:
Closed-canopy native coastal strand forest with sandy soils and native vegetation such as
Barringtonia asiatica, Bikkia tetrandra
(torchwood, gausåli),
Casuarina equisetifolia, Cocos nucifera, Hernandia nymphaeifolia
(doko, Hernandia, Jack-in-the-box, lantern tree, nonak),
Hibiscus tiliaceus, Ipomoea pes-caprae, Mammea odorata, Pemphis acidula
(bantigue, nigas),
Scaevola taccada, Sesuvium portulacastrum
(sea purselane),
Sporobolus virginicus
(banalo, binalo, Pacific rosewood, Portia tree),
Thespesia populnea
(banalo, binalo, Pacific rosewood, Portia tree),
Thuarea involuta
(kuroiwa grass, tropical beachgrass, bird's beak grass), and
Vigna marina.
c.
Cycas micronesica PBF 3:
Native pollinators such as moths and beetles, and native vegetation to support them.
d.
Cycas micronesica PBF 4:
Native seed dispersers such as birds and fruit bats.
Cycas micronesica
is a rare gymnosperm (usually an unbranched tree with a thick trunk) native to Guam, Rota, and possibly Pagan, where it is found in the limestone and volcanic forests and coastal (strand) habitats
(Service 2020ac, p. 9; Service 2023l, pp. 3, 11-12). Populations were continuous across Guam as recently as 2002, but fragmented after the cycad aulacaspis scale (
Aulacaspis yasumatsui
) was first detected in 2003. Once established, infestations spread rapidly and are extremely difficult to control, and there is no chemical or biological control method effective at a landscape scale. This invasive armored scale insect infests leaves, stems, and roots of
Cycas micronesica,
causing extensive tissue damage, defoliation, and eventually death. Since its introduction,
Aulacaspis yasumatsui
has caused declines in
Cycas micronesica
populations throughout its range, with mortality rates of up to 93 percent across all life stages, from seedlings to mature plants (Marler 2013, pers. comm). The continued presence of the cycad scale as a primary threat to
Cycas micronesica
increases its risk of extinction throughout its range.
Cycas micronesica
is unique among Mariana Islands species as the only native gymnosperm (seed producer), has nitrogen-fixing root symbionts (organisms living in symbiosis with another), lives up to 40 years (Bösenberg 2022, p. 8), and hosts the specialist native beetle
Dihammus marianarum
that feeds on stem tissue and a specialist native moth pollinator (
Anatrachyntis
sp.) that feeds on dispensable male cone tissue (Marler and Dongol 2016, p. 4; Service 2020i, p. 7; Service 2023l, p. 10).
Cycas micronesica
is food for the Mariana fruit bat and was historically used by humans as food after much processing. Threats to this species include loss and degradation of habitat due to impacts from invasive animal and plant species, development, wildfire, and climate change (
e.g.,
changes in precipitation patterns); herbivory from nonnative invertebrates and ungulates; and catastrophic events such as typhoons (Service 2023l, pp. 3, 17-19).
Cycas micronesica
reproduces vegetatively and sexually and requires pollinators (Service 2023l, p. 12) such as moths and beetles (
Carpophilus
spp. beetles, Nitidulidae family), it hosts native insect pollinator species, and pollen is dispersed by wind from April to August during the dry season (Hamada et al. 2015, entire; Schneider et al. 2002, p. 282; Service 2020i, p. 7; Service 2020m, p. 7; Terry et al. 2009, pp. 83, 96). Males create very strongly scented cones when pollen matures, and females produce a cone-like structure that opens outward to receive fertilization by pollen (Service 2023l, p. 9). Specialist pollinators are attracted to the cones' chemical cues (Schneider et al. 2002, p. 282; Terry et al. 2009, pp. 83, 96). Seeds require 3 to 6 months to germinate (Raulerson and Rinehart 1991, p. 4; Service 2023l, p. 9).
(9) Eugenia bryanii PBFs
a.
Eugenia bryanii PBF 1:
Limestone forests with moisture, including (but not limited to) forest edge perimeters, exposed limestone cliffs, and limestone forests with karst as the primary substrate.
b.
Eugenia bryanii PBF 2:
Native seed dispersers such as birds and fruit bats.
c.
Eugenia bryanii PBF 3:
Native pollinators and native vegetation to support them.
Eugenia bryanii
are small-to-medium-sized shrubs in the Myrtaceae family and are endemic to Guam, where they comprise part of the shrub community in limestone forest habitats, where limestone karst is the primary substrate; the species occupies a relatively narrow habitat niche along the perimeter of forest edges and exposed limestone cliffs (Costion and Lorence 2012, pp. 54, 82; Service 2020ae, p. 3; Service 2023n, pp. 3, 11). The species occurs in limestone forests where limestone karst is the primary substrate. However, it is unknown whether the species has any habitat requirements or limitations besides needing limestone soils or limestone karst, and it may previously have been more widely distributed; fewer ungulates can traverse karst substrates, potentially explaining why the species is only found along these edges (Service 2020k, pp. 7-8; Service 2023n, p. 11). Like other forest plants on Guam, the species likely requires pollinators, seed dispersers, water availability and vegetation communities consistent with native limestone forests, sunlight levels consistent with limestone karst forest edge habitat, limestone substrates, seasonal precipitation fluctuations, and relatively constant temperatures (Service 2023n, p. 12). Threats to this species include loss and degradation of habitat due to impacts from human activity and development, invasive species (
e.g.,
invertebrates and grazing by ungulates), and climate change (
i.e.,
increasing variability in temperatures, more severe alternating periods of droughts and floods, stronger typhoons) (Service 2023n, pp. 14-15).
Seeds require undisturbed substrates and moisture to survive. They are sensitive to desiccation, which affects seed germination and survival (Andrade et al. 2003, p. 131; Maluf et al. 2003, p. 471), and are dispersed by seed-eating birds and fruit bats (Gawel et al. 2018, p. 8). Habitats free from invasive pests are required for seed survival. Seed survival can be reduced by these factors: rats eat plants and seeds (possibly dispersing seeds as well); ungulates eat and crush plants and prevent regeneration; snakes remove plant-pollinating and seed-dispersing birds; and invasive plants outcompete native plants and overgrow native vegetation communities.
(10) Heritiera longipetiolata PBFs
a.
Heritiera longipetiolata PBF 1:
Closed-canopy native limestone forests where there are substrates of karsts, clifflines, and outcroppings.
b.
Heritiera longipetiolata PBF 2:
Sufficient space within limestone vegetation communities composed of plants such as (but not limited to)
Asplenium nidus, Hibiscus tiliaceus, Morinda citrifolia, Phymatosorus scolopendria,
Psychotria mariana,
and
Abrus
spp.,
Aidia
spp.,
Aglaia
spp.,
Ficus
spp.,
Freycinetia
spp.,
Melanolepis
spp.,
Operculina
spp.,
Pandanus
spp., and
Pipturus
spp.
c.
Heritiera longipetiolata PBF 3:
Individuals in close proximity to each other and adequate access by native seed dispersers such as birds and fruit bats.
d.
Heritiera longipetiolata PBF 4:
Native pollinators and native vegetation to support them.
Heritiera longipetiolata,
a medium to large hibiscus tree in the Malvaceae family, is found in the limestone forest habitats of Guam, Tinian, Saipan, and Rota where there are substrates of karst, clifflines, or outcroppings (Service 2023p, p. 10; Willsey et al. 2019, p. 4). Tree roots grow into rough limestone crevices, especially on cliffs and plateaus (Raulerson and Rinehart 1991, p. 94). On Tinian,
Heritiera longipetiolata
are observed only in karsts within native limestone forest (Stone 1970, p. 420; Service 2020m, pp. 7-8; DoN 2018, in litt., entire). The species is restricted to native limestone forest habitats where they are considered a canopy tree (University of Guam (UOG) 2018, in litt., pp. 5, 11, 40) comprising a closed-canopy system of broadleaf trees with an understory of younger trees, vines, epiphytic ferns, and orchids (Stone 1970, pp. 419-420; Vogt and Williams 2018, p. 66; Willsey et al. 2019, p. 3). Specifically, these forests contain upper canopy tall trees (33 ft; 10 m or taller), mid-story small to mid-size trees (10 to 33 ft (3 to 10 m)), and an understory of shrubs and herbs (Falanruw et al. 1989, pp. 6, 8). The vegetation community comprises species commonly associated with limestone forests including (but not limited to)
Asplenium nidus, Hibiscus tiliaceus, Morinda citrifolia,
Phymatosorus scolopendria, Psychotria mariana, Abrus
spp.,
Aidia
spp.,
Aglaia
spp.,
Ficus
spp.,
Freycinetia
spp.,
Melanolepis
spp.,
Operculina
spp.,
Pandanus
spp., and
Pipturus
spp. (Willsey et al. 2019, pp. 5-6; Service 2023p, p. 12). Threats to this species include loss and degradation of habitat due to impacts from invasive animal and plant species, development, and climate change (
i.e.,
increased precipitation and increased typhoon intensity and severity); loss of pollinators due to brown tree snake; herbivory by pigs, deer, rodents, invasive invertebrates, and leaf miners; and plant pathogens (Service 2023p, pp. 17-19).
Heritiera longipetiolata
requires sufficient space for sexual and vegetative reproduction because individuals grow in clusters and compete for sunlight and space (Service 2020m, p. 7). Sexual reproduction requires close proximity to other conspecifics where pollinators and seed dispersers can access individuals (Service 2020ag, p. 9; Hawaii and Pacific Plants Recovery Coordinating Committee (HPPRCC) 2011, p. 1). Seed dispersers, such as fruit-eating animals like native birds and fruit bats, are necessary for population growth and maintaining genetic diversity (Service 2023p, p. 13). Mutualists (
i.e.,
an organism that associates with a different species and both benefit), such as
H. longipetiolata,
require abundant and reliable sources of nectar, pollen, and fruits, and absence or low abundance of invasive animals such as the brown tree snake and rodents (Service 2023p, pp. 12-13).
(11) Maesa walkeri PBFs
a.
Maesa walkeri PBF 1:
Native limestone forest and forest edge habitats ranging in elevation between 656-1,312 ft (200-400 m).
b.
Maesa walkeri PBF 2:
Adequate sunlight, variable amounts of moisture, and relatively constant temperatures.
c.
Maesa walkeri PBF 3:
Native vegetation such as
Pandanus
spp., and
Hernandia-Elaeocarpus.
d.
Maesa walkeri PBF 4:
Native seed dispersers such as birds and fruit bats.
e.
Maesa walkeri PBF 5:
Native pollinators such as insects and native vegetation to support them.
Maesa walkeri
are small to medium shrubs (family Myrsinaceae) endemic to Guam and Rota limestone forests; they are most common along sunny edges of
Pandanus
spp. forests in limestone substrate or karsts, at 656-1312 ft (200-400 m) elevation, where there are variable amounts of moisture and relatively constant temperatures (Fosberg and Sachet, 1979, pp. 368-369; Fosberg 1960, pp. 22, 42; Raulerson and Rinehart 1991, p. 67; Costion and Lorence 2012, p. 84; Service 2020n; p. 6; Service 2020ai, p. 7; Service 2023q, pp. 3, 5, 10, 11).
Maesa walkeri
are strongly tied to the extent and amount of limestone forest habitat (Service 2023q, p. 13). Survival of the species depends on a number of genetically well-maintained populations that can exchange genes. This requires population distributions across a variety of habitat types (Service 2020ai, pp. 7-8).
Maesa walkeri
is most abundant in grassland/
Pandanus
spp. forest edges, lesser in forest/abandoned pasture edges and species in the
Hernandia
and
Elaeocarpus
family (referred to as
Hernandia-Elaeocarpus
) canopy with
Pandanus tectorius
understory, and least abundant in
Pandanus
spp. forest/road edges (Service 2023q, pp. 10-11). Threats to this species include loss and degradation of habitat due to impacts from development, feral ungulates, and brown tree snakes; predation by rats, and climate change (
i.e.,
increased periods of drought and severe storm frequency) (Service 2023q, pp. 3, 14-15).
Maesa walkeri
produces fruit and is assumed to be pollinated by insects (Service 2023q, p. 10). The species reproduces sexually and vegetatively (Service 2023q, pp. 6, 10). Seeds are likely dispersed by native fruit-eating birds fruit bat (Gawel et al. 2018, p. 8; Service 2023q, pp. 10, 11), and seed dispersers are required for recruitment and maintaining genetic diversity (Service 2023q, pp. 11, 14, 16; Wandrag et al. 2015, p. 1).
(12) Nervilia jacksoniae PBFs
a.
Nervilia jacksoniae PBF 1:
Connected closed-canopy native limestone, volcanic ravine, and mixed forests with leaf-littered humus or sandy forest floors, shade, minor to moderate light, and moisture.
b.
Nervilia jacksoniae PBF 2:
Native limestone forest understory with plants such as (but not limited to)
Elaeocarpus joga, Hernandia labyrinthica, Pandanus dubius
(påhong, bakong, or knob-fruited screwpine),
Pandanus tectorius, Pisonia umbellifera,
and
Psychotria malaspinae.
c.
Nervilia jacksoniae PBF 3:
Native volcanic forest understory with plants such as (but not limited to)
Barringtonia asiatica, Hernandia sonora, Pandanus tectorius, Pisonia grandis,
and
Terminalia catappa.
d.
Nervilia jacksoniae PBF 4:
Pollinators including insects, such as small bees and wasps, and native vegetation to support them.
This ground orchid is a small terrestrial herb in the Orchidaceae family that grows in canopy-covered, shady, moist, leaf-littered humus or sand on forest floors of Guam and Rota; the orchids are found only in native limestone and mixed-forest subtypes and native volcanic forests of ravines in southern Guam (Service 2020o, p. 8; Service 2023r, pp. 5, 14). The species requires soils with sand or humus (Service 2020aj, p. 14) for its subterranean reproductive tuber to grow; it then rises to produce a flower and seed pods that are dispersed by wind (Service 2023r, p. 8).
Nervilia jacksoniae
occur only where there is minor to moderate moisture because all life stages require precipitation during both rainy and dry seasons (Service 2020aj, p. 14; Service 2023r, pp. 9, 14).
Nervilia jacksoniae
requires plant genera and substrates typical of native limestone or volcanic forests in the Mariana Islands, growing under native plants in limestone substrates such as
Pandanus tectorius, Pandanus dubius,
Hernandia labyrinthica, Elaeocarpus joga, Pisonia umbellifera,
and the federally endangered
Psychotria malaspinae
(Service 2020aj, pp. 9, 14) and growing under native plants in volcanic substrates such as
Pisonia grandis, Hernandia sonora, Barringtonia asiatica, Pandanus tectorius,
and
Terminalia catappa
(Willsey et al. 2019, pp. 5-6). Species observations are limited to areas containing shade with minor to moderate filtered light (Service 2020aj, p. 14; Service 2023r, p. 9). Substrate required for volcanic forests are volcanic soils and associated plant species that may include
Pisonia grandis, Hernandia sonora, Barringtonia asiatica, Pandanus tectorius,
and
Terminalia catappa
(Willsey et al. 2019, pp. 5-6).
Reproduction requires wind and rain for seed dispersal (Service 2020aj, p. 15; Service 2023r, pp. 5, 17) and pollination by insects, such as small bees and wasps (Pettersson 1991, p. 19; Service 2020aj, p. 16). The flowers of the plant evolved to attach pollen masses to the stigma of the flower (Johnson and Edwards 2000, pp. 243, 255; Mosquera-Mosquera et al. 2019, pp. 363, 365-366). However, if there is an inadequate number of individual plants present, they are unlikely to attract pollinators (Gale 2007, p. 59). Germination rates are likely very low on forest floors (0 to 12 percent) compared to in vitro cultured seeds (76 to 99 percent) (Gale et al. 2010, p. 166), possibly caused by a lack of mycorrhizal fungi for seed development, and sometimes bacteria, which many orchid species require (Alghamdi 2019, p. 502; Gale et al. 2010,
pp. 166, 175; Ray and Vadramne 2015, p. 2; Tsavkelova et al. 2007, pp. 69, 75). Fungi play an important role in overcoming light inhibition of seed germination (Alghamdi 2019, p. 495). Reproduction also occurs by vegetative growth through multiple tuber development (Service 2023r, p. 8) requiring adequate space in humus and sand to allow new tubers to develop (Service 2020aj, pp. 14-15).
Nervilia jacksoniae
reproduction and survival requires minimal disturbance. However, habitat disturbance is frequent on Guam and caused by nonnative pigs, water buffalo (
Bubalus bubalis
), deer, rats, reptiles (
e.g.,
brown tree snakes), invertebrates (
e.g.,
cycad scale, slugs (
e.g.,
pancake slug (
Veronicella sloanii
)), and snails (
e.g.,
giant African land snail) (80 FR 59424 at 59437 and 59449, October 1, 2015; Willsey et al. 2019, p. 16). On Rota, reproduction and survival can be inhibited by deer, rats, and invertebrates (
e.g.,
cycad scale, slugs, and snails) because they eat, trample, or otherwise destroy seeds and plants (80 FR 59424 at 59437 and 59449, October 1, 2015; Willsey et al. 2019, p. 16). In addition to the habitat-based threats from invasive, nonnative animals,
N. jacksoniae
experiences loss and degradation of habitat due to impacts from invasive plants, development, wildfire, and climate change (
i.e.,
increased precipitation, typhoon intensity, and frequency) (Service 2023r, pp. 20-25).
(13) Psychotria malaspinae PBFs
a.
Psychotria malaspinae PBF 1:
Interconnected native limestone forest habitat.
b.
Psychotria malaspinae PBF 2:
Sufficient space within a vegetation community where there is closed canopy or where partial to full sunlight is available with plants such as (but not limited to)
Abrus
spp.,
Aglaia mariannensis, Aidia cochinchinensis, Asplenium nidus,
Ficus
spp.,
Freycinetia
spp.,
Hibiscus tiliaceus, Melanolepis multiglandulosa, Morinda citrifolia, Operculina
spp.,
Pandanus
spp.,
Phymatosorus scolopendria, Pipturus argenteus
(amahåyan, atmahåyan, amahadyan, ghasooso, native mulberry), and
Psychotria mariana.
c.
Psychotria malaspinae PBF 3:
Native seed dispersers such as birds and fruit bats.
d.
Psychotria malaspinae PBF 4:
Native pollinators and native vegetation to support them.
Psychotria malaspinae,
a rare endemic shrub or small tree in the Rubiaceae family, is found only in undisturbed, connected, native limestone forests with limestone soils and karsts on Guam (Service 2020ak, pp. 8, 9, 13, 16; Service 2023t, pp. 9-10; Stone 1970, pp. 554-555). The species requires predominantly native vegetation typical of limestone forests in the Mariana Islands that provide for their reproduction and recruitment (for specific vegetation species see Raulerson and Rinehart 1991, p. 83; Service 2020ak, p. 9; Service 2023t, p. 10; Stone 1970, pp. 554-555; Willsey et al. 2019, pp. 5-6), including closed canopy of broadleaf trees with an understory of younger trees, vines, epiphytic ferns, and orchids (Stone 1970, pp. 554-555; Vogt and Williams 2018, p. 66); tall trees (32 ft (10 m)) comprising the upper canopy, small to mid-size trees (10 to 33 ft (3 to 10 m)) as mid-story, and shrubs and herbs that form the understory (Falanruw et al. 1989, pp. 6, 8).
Population connectivity results when seeds are dispersed across contiguous limestone forests, and this is necessary to maintain genetic diversity in multiple populations (Service 2020p, pp. 8-9; Service 2023t, p. 14). More than 83 percent of Guam's native forests are gone or have severely impaired habitat connectivity (Service 2020an, p. 3), but this species' persistence has been attributed to its distribution in native limestone forests (Service 2023t, p. 15). Fruits and flowers are eaten and dispersed by birds (Service 2023t, p. 9), which may account for the current scattered distribution of the remaining populations within the forest ecosystems on the northeast and southeast sides of Guam (Stone 1970, pp. 554-555; Raulerson and Rinehart 1991, p. 83; Costion and Lorence 2012, pp. 54, 85-86, 96).
Seed dispersers are required to ensure seeds are moved farther away from conspecifics allowing for increased recruitment to grow the populations and to maintain genetic diversity (Service 2023t, p. 14; Service 2020p, p. 9). Deposited seeds have low germination rates and sow themselves nearby and produce seedlings (Service 2023t, p. 9). Invasive ungulates and rodents cause significant rates of mortality to seedlings and immature plants (
i.e.,
by eating the seeds or disturbing soils and substrates, exposing the seeds and ultimately killing them) (Kessler 2011, p. 320; Rubinoff and Holland 2018, pp. 222-224). The species requires pollination and seed dispersal by native species, including birds. As stated previously, pollinators and birds are almost entirely absent from Guam (Egerer et al. 2018, p. 655; Service 2020ak, pp. 2, 14). Threats to this species include loss and degradation of habitat due to impacts from invasive animal (
e.g.,
brown tree snake) and plant (
e.g.,
vines) species, development, and increasing typhoon intensity; loss of pollinators due to brown tree snake and rodents; herbivory by pigs, Philippine deer, and rodents (Service 2023t, pp. 3, 15-16).
(14)
Tabernaemontana rotensis
PBFs
a.
Tabernaemontana rotensis PBF 1:
Interconnected native limestone forests, open patches, and forest edges providing moderate to full sunlight.
b.
Tabernaemontana rotensis PBF 2:
Native limestone forest habitat vegetation such as (but not limited to)
Abrus
spp.,
Aidia
spp.,
Aglaia
spp.,
Aglaia mariannensis, Aidia cochinchinensis, Asplenium nidus, Elaeocarpus
spp.,
Ficus
spp.,
Freycinetia
spp.,
Guamia
spp.,
Hernandia
spp.,
Hibiscus tiliaceus, Intsia bijuga, Macaranga thompsonii, Melanolepis
spp.,
Morinda citrifolia, Operculina
spp.,
Pandanus
spp.,
Phymatosorus scolopendria, Pipturus
spp.,
Pisonia grandis, Pouteria
spp.,
Premna
spp.,
Psychotria mariana,
and
Trema
spp.
c.
Tabernaemontana rotensis PBF 3:
Native seed dispersers such as birds and fruit bats.
d.
Tabernaemontana rotensis PBF 4:
Native pollinators, such as butterflies and other generalist pollinators, and native vegetation to support them.
Tabernaemontana rotensis
is a medium-sized tree (approximately 30 ft (9 m) tall) in the Apocynaceae family that requires interconnected limestone forest habitat dominated by native vegetation (Service 2020al, pp. 10-11; UOG 2007, in litt., pp. 4, 11), which is found only in the limestone forest habitat of Guam and Rota (Stone 1970, p. 485). The species requires sufficient limestone forests with limestone soils and karst for reproduction and recruitment, pollinators, and plant species typical of a native limestone forest in the Mariana Islands, which may include the species noted above in PBF 2 (Service 2020al, p. 11; Willsey et al. 2019, pp. 5-6). Sufficient space is needed for the species to reproduce sexually or vegetatively (Service 2020al, p. 10), preferably in open patches or forest edges where partial to full sunlight is available (Service 2020al, p. 10; UOG 2007, in litt., pp. 4, 14-15). Germination and seedling emergence are maximized in partial to full sunlight conditions if an adequate seed bank is available (UOG 2007, pp. 4, 14-15). Threats to this species include loss and degradation of habitat due to impacts from invasive animal (
e.g.,
brown tree snake) and plant (
e.g.,
vines) species, development, fire, and climate change
(
i.e.,
typhoons with intense winds); loss of pollinators from brown tree snake and rodents; herbivory by invasive invertebrates and rodents; and trampling by ungulates (
i.e.,
pigs and Philippine deer) (Service 2023t, pp. 3, 15-17).
Tabernaemontana rotensis
population distribution is clustered because seedling establishment is restricted to the vicinity of the parent tree due to the loss of frugivorous bird species on Guam (from being depredated by brown tree snakes) (UOG 2007, pp. 4-5, 9, 28; Service 2017, pp. 80-82). The species requires seed dispersers and contiguous limestone forest for population growth, maintaining genetic diversity (Service 2020al, p. 11), aiding recruitment, and ensuring seeds are dispersed away from conspecifics to increase recruitment (Service 2023v, p. 16). Without dispersal from the parent, the seeds develop in extreme competition with each other, and almost complete mortality occurs (Rogers et al. 2017, p. 2; Service 2023v, p. 16; UOG 2007, pp. 22, 73). Fruit-eating animals benefit plant recruitment by increasing germination during gut passage and moving seeds away from the parent plants, consequently increasing distribution and resiliency of the species (Service 2020al, p. 11). The pollinators are sustained by abundant, diverse, and reliable sources of native nectar and pollen plants, and stable habitats that are sufficiently free of nonnative plants and animals (
i.e.,
invertebrates, brown tree snake, rodents, and ungulates) (Service 2020q, pp. 6-7, 9, 12, 20; Service 2020al, p. 11; Service 2023v, p. 3).
(15) Tinospora homosepala PBFs
a.
Tinospora homosepala PBF 1:
Tall-canopy native limestone forests with limestone soils and karst substrates.
b.
Tinospora homosepala PBF 2:
Native pollinators and native vegetation to support them.
c.
Tinospora homosepala PBF 3:
Native seed dispersers such as native birds and fruit bats.
Tinospora homosepala
is a woody, climbing vine in the Menispermaceae family that comprises the shrub or herbaceous components of the limestone forest ecosystem of central Guam (Service 2023w, p. 5). The species requires limestone soils to limestone karst, its primary substrate, and can inhabit backstrand habitat. It is most likely found where there are tall trees that it can climb, likely to obtain levels of sunlight consistent with limestone karst forest edge habitat (GPEPP 2024, in litt., entire; Service 2020am, pp. 9-10). Seasonal fluctuations (wet and dry season) typical of the Mariana Islands may be necessary for completion of its life cycle (Service 2020am, p. 6), as are relatively constant temperature ranges and precipitation requirements consistent with native limestone forests (Ohba 1994, pp. 13-16; Mueller-Dombois and Fosberg 1998, p. 241; Service 2023w, p. 9).
Tinospora homosepala
reproduces both sexually and vegetatively and is limited by the very low population abundance of 150 individuals spread across only 4 locations; 120 of the plants are from 1 population, and the sexes of the plants are unknown (Service 2023w, p. 13). Sexual reproduction requires male and female plants and pollination from insects (Service 2020am, pp. 6-7). Reproduction also occurs via cloning (unisexual), in which severed vines send new roots into the ground (Stone 1970, p. 277; Service 2023w, p. 9). Seed-dispersing vertebrates, such as Mariana fruit bat, Mariana crow (
Corvus kubaryi
), and Micronesian megapode (
Megapodius laperouse
) are also likely necessary, because otherwise the plants would deposit their seeds directly below themselves with little successful reproduction due to low light, competition with more established plants, and high seed density (Willsey et al. 2019, p. 3).
Nonnative animals have severely degraded the habitat and life history requirements of
Tinospora homosepala.
The invasive brown tree snake decimated the avian and small animal community that likely functioned as seed dispersers (Service 2020r, pp. 8-9). Rodents eliminated native plant species by eating the plants and their seeds (although they possibly disperse seeds as well) (Service 2020r, pp. 8-9). Nonnative invertebrates kill and otherwise reduce the abundance of native invertebrates that likely serve as pollinators and provide other functions supporting a healthy ecosystem (Service 2020r, pp. 8-9). In addition to the nonnative brown tree snake, rodents, and other invertebrates previously discussed, the fruit-piercing moth (
Eudocima fullonia
) is an especially damaging invasive invertebrate that severely reduces the female vines' fruit production by puncturing it, causing the fruit to rot and decay (only female vines' fruit), with only male plants remaining (Service 2023w, p. 14). Other threats include loss and degradation of habitat due to development, feral ungulates, and climate change (
i.e.,
increased period of droughts and severe storm frequency) (Service 2023w, pp. 3, 11-12).
Savanna Plants
This rare Guam savanna habitat rises from highly weathered volcanic clay soils, and its distribution is associated with volcanic clay substratum (Service 2020af, p. 11; Service 2023o, p. 10). The volcanic clay soils are highly acidic in most places from the abundance of aluminum in the soil (Mueller-Dombois and Fosberg, 1998, pp. 269-270; Carroll and Hathaway 1963, pp. 29-30) and are characterized as nutrient deficient (Bojórquez-Quintal et al. 2017, pp. 1-4). Soils containing aqueous aluminum may stimulate plant growth by promoting nutrient intake depending on the environmental conditions, concentration of the aluminum, and the plant species (Bojórquez-Quintal et al. 2017, pp. 2-10). This savanna habitat has a uniquely stable climate with daily temperatures ranging between 73 and 86 °F (22 and 30 °C), 6 to 8 hours of sunlight, distinct dry and wet seasons averaging 96 in (218 centimeters (cm)) of rain annually, and underlying volcanic substratum with very low porosity causing most rainwater to run off into streams and the ocean (Service 2020af, p. 15; Service 2023o, p. 14). There are five plant communities in the savanna habitat, including (1)
Miscanthus
(silver grass or maiden grass), (2)
Dimeria
spp. (a type of woody/herbaceous grass), (3) erosion scar (pioneer species of grasses, ferns, and shrubs within heavily eroded savanna areas), (4)
Phragmites
(common reed), and (5) the weed community which follows disturbance (Fosberg 1960, pp. 64-66).
(16)
Hedyotis megalantha PBFs
a.
Hedyotis megalantha PBF 1:
Native savanna habitats with volcanic soils.
b.
Hedyotis megalantha PBF 2:
Grasses, ferns, shrubs, and other savanna vegetation such as (but not limited to)
Decaspermum fruticosum
(no common name),
Dicranopteris linearis
(Old World forked fern, uluhe, chacha),
Dimeria
spp.,
Fimbristylis
spp.,
Geniostoma micranthum
(no common name),
Lycopodium cernuum
(påtas ngånga', staghorn clubmoss, nodding clubmoss),
Machaerina mariscoides
(tropical twigrush),
Melastoma malabathricum
var.
mariannum
(melastoma, gafao, gafau),
Myrtella benningseniana
(no common name),
Phyllanthus saffordii,
and
Rhynchospora rubra
(sweet broom, macao tea).
c.
Hedyotis megalantha PBF 3:
Native pollinators, such as butterflies and other generalist pollinators, and native vegetation to support them.
Hedyotis megalantha
is a long-lived woody herb in the coffee family Rubiaceae and is endemic to Guam savanna (Global Biodiversity Information Facility 2024, website; Mueller-Dombois and Fosberg 1998, pp. 269-270; UOG 2018, in litt., pp. 10-11; Service 2020af, p. 7; Service 2023o, pp. 3, 10, 13).
Hedyotis megalantha
may require acidic soils for optimal growth, but research on other
Hedyotis
species indicates a preference for acidic soils, not confinement to them (Fosberg 1960, pp. 22-23, 31-32, 34-35; Service 2020af, p. 15). The species may require only minimal nutrients for survival or may have an enhanced ability to absorb soil nutrients (Service 2023o, p. 14).
Hedyotis megalantha
benefits from the presence of aqueous aluminum and may have other biological mechanisms allowing its survival in low-nutrient environments, including a symbiotic relationship with the microbial community or through commensalism (where a species receives benefits but there are no effects on the other organism) (Service 2020l, p. 7; Service 2023o, p. 14). Threats to this species include loss and degradation of habitat due to impacts from development, nonnative animals and plants, wildfire, erosion, off-road vehicle use, and possibly changes in frequency and intensity of precipitation and typhoon events (Service 2023o, pp. 3, 18-25).
Hedyotis megalantha
is limited primarily to high-quality native savanna habitat with little human disturbance, often found growing in clusters with native ferns including
Dicranopteris linearis,
in
Dimeria
spp. plant communities, and in erosion scar communities (Frager et al. 2019, p. 4; Demeulenaere 2020, in litt., entire; Service 2020l, pp. 6-7; Service 2023o, pp. 10, 14).
Dimeria
spp. communities are dominated by
Dimeria chloridiformis
(no common name), a low-growing grass, with
Hedyotis megalantha
and
Phyllanthus saffordii
scattered throughout (Demeulenaere 2020, in litt., entire). Erosion scar communities contain
Hedyotis megalantha
growing in between low-growing shrubs such as
Melastoma malabathricum
var.
mariannum, Decaspermum fruticosum, Myrtella benningseniana, Phyllanthus saffordii,
and
Geniostoma micranthum;
low-growing sedges such as
Rhynchospora rubra, Fimbristylis
spp., and
Machaerina mariscoides
(relatively taller than
Hedyotis megalantha
); and ferns such as
Lycopodium cernuum,
and
Dicranopteris linearis
(Demeulenaere 2020, in litt., entire; Service 2020l, pp. 6-7; Service 2023o, p. 14).
Hedyotis megalantha
reproduction may include self-pollination, inability to self-pollinate, and sexual reproduction; no studies have yet determined the breeding system (Service 2023o, p. 15). Pollinators are undocumented but the species likely requires cross-pollination for optimal breeding success, with pollinators likely consisting of a variety of insects similar to other species within the genus
Hedyotis
(Service 2020l, p. 7). The white flowers with purple anthers of
Hedyotis megalantha
may attract butterflies and other generalist insect pollinator species. Seed dispersal for
Hedyotis megalantha
likely occurs via abiotic factors such as wind, gravity, or water (Service 2020af, p. 17; Service 2023o, p. 16). Seeding likely occurs during the wet season, maturing occurs into the dry season, and the species may require dry seasons to set fruit and for seed germination (Service 2023o, pp. 15-16). Prolonged hours of sunlight may be needed for both seed germination and for seedlings to mature, including production of the next generation of seeds (Service 2020af, p. 15; Service 2023o, p. 14).
(17) Phyllanthus saffordii PBFs
a.
Phyllanthus saffordii PBF 1:
Savanna habitats with volcanic substrates containing lateritic soils, including (but not limited to)
Dimeria
spp. communities and erosion scar communities.
b.
Phyllanthus saffordii PBF 2:
Forest edges, steep slopes, and eroded soils on volcanic substrates containing lateritic soils.
c.
Phyllanthus saffordii PBF 3:
Savanna vegetation such as (but not limited to)
Decaspermum fruticosum, Dicranopteris linearis, Dimeria chloridiformis, Fimbristylis
spp.,
Geniostoma micranthum, Melastoma malabathricum
var.
mariannum, Myrtella benningseniana, Machaerina mariscoides, Lycopodium cernuum, Phyllanthus saffordii,
and
Rhynchospora rubra.
d.
Phyllanthus saffordii PBF 4:
Native pollinators, such as bees, ants, moths, butterflies, and other generalist pollinators, and native vegetation to support them.
e.
Phyllanthus saffordii PBF 5:
Native seed dispersers such as birds and fruit bats.
Phyllanthus saffordii
is a short-stature and short-lived woody shrub in the Phyllanthaceae family and persists only in southern Guam in the savanna habitats with deeply weathered volcanic substrates that contain lateritic soils (high iron and aluminum content, red clay, and highly acidic), including erosion scar and
Dimeria
spp. communities, and the plants are also found along forest edges, steep slopes, and severely eroded soils; the species does not occur in alkaline soils of northern Guam (Service 2020s, p. 5; Service 2023s, pp. 2, 15). The species most commonly occurs among other low-growing plants including the native grass
Dimeria chloridiformis,
and among the native scar community, consisting of the low-growing shrubs, low-growing sedges, and fern species identified above (Demeulenaere 2020, in litt., entire). Both
Phyllanthus saffordii
and
Hedyotis megalantha
can be found growing between grass, sedges, shrubs, and ferns (Demeulenaere 2020, in litt., entire; Service 2023s, p. 4). Threats to this species include loss and degradation of habitat due to impacts from development, invasive animals (
e.g.,
ungulates) and plants (
e.g.,
nonnative grasses), erosion, wildfire, and climate change (
i.e.,
increased precipitation and increased typhoon intensity and frequency) (Service 2023s, pp. 16-23).
Like other species within the
Phyllanthus
genus,
Phyllanthus saffordii
likely relies on bees, ants, moths, butterflies, and other generalist pollinators rather than avian or fruit bat or wind for pollination (Kawakita 2010, p. 13; Service 2020y, p. 13).
Phyllanthus saffordii
is not known to be capable of self-pollinating or reproducing without fertilization (Service 2023s, p. 14; Sharma et al. 2009, p. 286).
Phyllanthus saffordii
likely depends on dry seasons for fruiting and seed germination, and seed dispersal likely involves fruit-eating avian species that distribute seeds (Prasad et al. 2004, entire; Service 2020y, p. 13; Service 2023s, p. 14). Prolonged hours of sunlight are likely needed for seed germination and for seedlings to mature, including the production of the next generation of seeds (Service 2020y, pp. 12-13).
Special Management Considerations or Protection
When designating critical habitat, we assess whether the specific areas within the geographical area occupied by the species at the time of listing contain features that are essential to the conservation of the species, and which may require special management considerations or protection. The specific PBFs essential to the conservation of the Mariana Islands species may require special management considerations or protection to reduce the threats affecting those features. Threats to the Mariana Islands species are described in the final listing rule (80 FR 59424; October 1, 2015) and summarized in this proposed
rule; noting that some information, descriptions, and references used herein are new since the final listing determination. The threats and associated special management considerations or protection addressed in this document are specific to the PBFs and grouped into six threat categories based on the primary threats to the PBFs. Each of these threats and associated special management considerations or protection are summarized below.
(1) Development—includes agricultural, military, urban, and commercial development, as well as activities associated with construction, repair, and maintenance of roads, bridges, and utilities (
e.g.,
power plants and renewable energy facilities).
Habitat clearing for development is among the greatest threats to the recovery of the Mariana Islands species. Development causes habitat loss and degradation by reducing the available habitat and foraging, breeding, and sheltering sites for the species (Service 2023a, p. 17). This may lead to habitat fragmentation, which separates populations, limits pollination, and can be deleterious to plant-pollinator mutualisms, especially invertebrates (Newman et al. 2013, p. 16). Many sites that species once occupied have been developed on several islands, thus reducing the amount of suitable habitat available for the species (80 FR 59424 at 59429-59430, October 1, 2015). Agricultural development can include land clearing to grow a wide range of agricultural products, including livestock (grazing), vegetable farms, and plant nurseries for commercial sale. Military development can include construction of housing and a wide variety of military activities, such as the placement and removal of objects, and unexploded ordnance management (although areas where this may occur are exempt under section 4(a)(3) of the Act (see Exemptions, below). Urban and commercial development can include the construction of residential homes and various commercial buildings, including parking lots.
Activities associated with development can include limestone rock quarrying; construction or maintenance of renewable power plants; and construction, repair, and maintenance of roads, bridges, and utilities including renewable energy. Actions associated with development also include stream diversions for municipal water supply that directly reduce the amount of available stream habitat annually (Service 2020aa, p. 4). For example, on the island of Rota, the reduction of and changes to forest landscape due to urban or agricultural development have changed the quantity and quality of the groundwater that the aquifer feeds to the island's streams. Additional/future impacts may also further degrade or reduce forest habitat and the capacity for the Sabana Plateau to replenish the aquifer water available for stream habitat (Service 2020aa, p. 50). Examples of special management and considerations or protections that could reduce the threat of development may include (but are not limited to):
• Use best management practices to limit or reduce erosion/stream sedimentation, retain natural barriers/culverts, or construct barriers that prevent erosion of the stream edge;
• Minimize the destruction of native forest vegetation, especially large-growth trees and species-specific host plants;
• Require qualified and experienced surveyors to conduct preconstruction surveys to locate and avoid listed species and PBFs;
• Conduct habitat restoration;
• Limit ground-disturbing activities;
• Cover open trenches and excavated pits and visually inspect excavated areas before backfilling;
• Implement stream stabilization and erosion control protocols;
• Create riparian buffers if land abuts streams to reduce soil erosion and filter water flowing from croplands;
• Restore disturbed areas using native plants once projects are completed;
• Avoid or limit vegetation and soil disturbance;
• Protect sensitive areas where they abut project boundaries by installing and maintaining plastic construction fencing or brightly colored flagging around these areas; and
• Use dust abatement techniques along roadways to minimize dust to vegetation.
(2) Invasive species—includes animals (ungulates, rodents, brown tree snake, ants, slugs) and nonnative plants.
Invasive animals (
e.g.,
ungulates, rodents, brown tree snake, ants, and slugs) degrade native forest, savanna, and stream habitats that are required by the Mariana Islands species. Ungulates damage mature vegetation and clear forest understory through grazing and trampling, contributing to erosion, and preventing the regeneration of seeds or seedlings by eating or damaging them (Service 2023a, pp. 17-18). They also contribute to the spread of invasive plants by transporting seeds and plant parts (Cuddihy and Stone 1990, p. 65). For Langford's tree snail, suitable habitat has been severely impacted on Aguiguan as nonnative goats have destroyed much of the forest on the island (Service 2020d, p. 5). Rodents reduce native plant reproduction and vigor by eating fruits, seeds, flowers, stems, roots, and other plant parts (Atkinson and Atkinson 2000, p. 23).
Forest degradation from invasive species is associated with declines in Slevin's skink populations, and skink populations increased following forest regeneration from ungulate removal on Sarigan and rodent eradication on Guam's Cocos Island (Kessler 2011, p. 320; Richmond et al. 2021, p. 69). Tree snails also increased in abundance within forested areas following ungulate removal on Sarigan (CNMI DFW 2008, p. 8-5). The ungulate removal on Sarigan Island was a mitigation measure that the U.S. Department of Navy (DoN) implemented to improve habitat and population sizes of the federally endangered Micronesian megapode (
Megapodius laperouse
) to offset the impacts of military bombing activities that occurred on Farallon de Medinilla.
Host plants for the Mariana eight-spot butterfly have become restricted to cliff edges and pinnacle karst terrain where they are less accessible to ungulates. Where brown tree snakes occur, they have caused the extirpation of most of the forest birds (and fruit bat) that were pollinators or seed dispersers (Fritts and Rodda 1998, p. 129). Invasive ants prey on vertebrate and invertebrate eggs, pupae, larvae, and adults as well as transport plant pests such as aphids, white flies, and scale insects, affecting the pollinators and seed dispersers required to maintain and grow native forests (Wild 2014, in litt., entire; Hawaii Invasive Species Council 2021, in litt., entire). Ants also exert direct predatory pressure on tree snails. Slugs damage both host plants of the Mariana eight-spot butterfly and other native forest plants, causing mortality and altering native forests (Service 2023a, p. 22). Invasive plants (
e.g., Spathodea campanulata
(African tulip tree),
Areca catechu, Citrus
sp.,
Cocos nucifera, Delonix regia
(flame tree),
Casuarina equisetifolia, Pithecellobium dulce
(kamachile),
Mangifera
sp. (mango),
Acacia confusa
(sosugi),
Leucaena leucocephala
(tangantångan),
Samanea saman
(trongkon-mames or monkeypod), and
Vitex parviflora
(vitex) forests degrade native forests by modifying light availability, soil-water regimes, nutrient cycling, fire regimes, and converting plant communities from native to nonnative (Willsey et al. 2019, pp. 5-6, 16-17). Invasive plants and ungulates may reduce water input into the aquifer feeding the streams (Service 2020aa, p. 34). Examples of special management considerations and protections that could reduce the threat
of invasive animals and nonnative vegetation may include (but are not limited to):
• Implement biosecurity protocols to prevent the introduction or movement of invasive species in or out of the project area;
• Conduct habitat restoration;
• Control or remove/eradicate ungulates, rodents, brown tree snakes, invasive invertebrates (
e.g.,
New Guinea flatworm, parasitic wasps, and ants), and significant habitat-modifying invasive plants; and
• Install and monitor exclusion fencing to prevent reintroduction of invasive species into project areas after eradication.
(3) Wildfire—Wildfire is not a part of the ecosystem in the Mariana Islands, and natural fires in the Mariana Islands are uncommon due to moist environmental conditions; however, hunters and poachers are known to intentionally ignite fires to encourage new plant growth to attract prey animals (Guam Department of Agriculture 2021, p. 67). These intentionally ignited fires can spread out of control to become a wildfire. Wildfires destroy individual plants and alter suitable habitat conditions, allowing nonnative plants to dominate plant communities after the fire. Fires in the forest and savanna can convert these habitats to bare ground or grasslands, leading to either colonization by invasive plants or conversion to bare ground that cannot support plant growth due to severe erosion (Willsey et al. 2019, p. 18). Fires in these habitats may also lead to erosion and deposits of silt into streams and the ocean (Guam Department of Agriculture 2021, p. 55). Areas converted to grass facilitate the spread of future fires and reduce the area of remaining suitable forest and savanna habitats each successive dry season (Tunison et al. 2001, p. 126). Examples of special management considerations or protection may include (but are not limited to):
• Restrict activities that entail the use of extreme heat to areas that are kept bare of vegetation, such as paved or maintained gravel areas;
• Limit activities that are potential fire risks to the wet season (July-December);
• Create and maintain a system of firebreak roads between action areas and suitable habitat for listed species;
• Prescribe burning, mowing, vegetation removal, or planting native vegetation that is more fire resistant; and
• Minimize destruction of forest vegetation when implementing fire management actions such as firebreaks, vegetation removal, or prescribed burning, especially large-growth trees and species-specific host trees/plants.
(4) Climate change—includes increase in typhoon frequency and changes to precipitation seasonality and temperature.
Potential impacts of climate change to the Mariana Islands species include an increase in typhoon intensity and alteration to normal ranges for precipitation and temperature due to extreme El Niño events. Ocean surface temperature increases are expected to result in increased typhoon intensity in the Mariana Islands and may result in changes to habitat by defoliating or uprooting trees or breaking primary branches and creating space for invasive, disturbance-tolerant species to dominate (Emanuel 2013, p. 12,219; Camargo 2013, p. 9,896; Grecni et al. 2021, p. 5). Typhoons exacerbate other threats and adversely affect habitat and food resources and pose a particular threat to small and isolated populations, such as the Pacific sheath-tailed bat population on Aguiguan (Service 2023a, pp. 17-24; Service 2020u, p. 12). Typhoons can also cause landslides or flooding. An increase in extreme El Niño events can change normal precipitation and temperature ranges that may exacerbate the wildfire threat, alter stream flows, and change microclimate and suitability of habitats that support the Mariana Islands species (Grecni et al. 2021, p. 23). Anticipated sea level rise and coastal erosion are expected to remove low-lying and coastal sites from future terrestrial species conservation use, coupled with the effects of typhoons (Grecni et al. 2021, pp. 27, 32-33).
Examples of special management considerations or protections that could reduce the negative effects of climate change may include (but are not limited to):
• Conduct habitat restoration and debris cleanup after typhoons;
• Implement erosion control protocols to protect coastal strand areas from sea level rise;
• Implement watershed management plans to maintain waterflow and decrease the effects of flooding; and
• Ensure communication with external partners on preferred response methodologies, such as post-typhoon debris cleanup to prevent the spread of invasive species and consultations with local partners on the typhoon recovery actions to protect or restore degraded habitat after typhoons.
(5) Recreational land use—includes the use of essential and nonessential off-roading vehicles and recreational access/use, such as hiking and camping.
Land use for recreational purposes may have an impact to the Mariana Islands species and their habitats. Off-road vehicle use through savanna and forest habitats reduces suitable habitat by increasing erosion. For example, within savanna habitat on the island of Rota, vehicles tend to consistently follow the same paths causing soil trails to deepen and worsen erosion, which deposits silt into streams and the ocean, altering the water quality of streams and ponds occupied by the Rota damselfly. Off-road vehicle use also compacts the soil, decreasing the soil porosity, which is already low for volcanic clay soils of the savanna, and increasing soil erosion (Swaddell 2024, in litt., entire). Recreational access to caves and forests occupied by the Pacific sheath-tailed bat may lead to roost abandonment and alter food availability for the bat (Service 2023a, p. 24). An increase in human activity may also lead to movement of invasive plants and animals in and out of recreational areas. Examples of special management considerations or protections that could reduce threats related to recreational land use may include (but are not limited to):
• Implement and enforce policies that restrict access to highly weathered off-road trails during the wet season when the possibility of soil erosion is higher;
• Implement habitat restoration projects to help contain sediments during the wet season;
• Plant native vegetation to stabilize highly weathered savanna habitat;
• Implement biosecurity protocols within conservation areas and educate the public on their use and effectiveness;
• Avoid or reroute off-road trails away from stream crossings or prioritize closure of these routes;
• Restore the areas where high levels of erosion occur;
• Conduct micropropagation and develop ex situ populations of federally listed plants; and
• Implement wildfire prevention protocols and educate the public on the prevention of wildfires in areas where hiking and camping occur.
(6) Pesticides—includes herbicides and insecticides.
This threat may injure or kill listed plants and animals or harm their habitat. Pesticides alter foraging habitat for listed animal species addressed in this proposed rule by disrupting the life cycle of forest vegetation through decreasing or removing pollinators and reducing the availability of food sources (
e.g.,
insect prey for the Pacific sheath-tailed bat and the Slevin's skink) (Kearns et al. 1998, entire; Service
2020u, pp. 11-12; Harrington et al. 2020, p. 14). Examples of special management considerations or protections that could reduce the threat of pesticides may include (but are not limited to):
• Limit use of insecticides, herbicides, or fungicides and follow labeled instructions, or use natural predators or remedies to reduce pests;
• Avoid applying pesticides during the wet season (July-December) or if rainfall is expected within 24 hours to decrease the likelihood that pesticides will wash into streams and rivers;
• Avoid applying pesticides when wind speed is greater than 12 mph and direction may cause it to drift to sensitive sites;
• Protect nontargeted species (vegetation, vertebrates, or invertebrates) by monitoring for drift or accidental application and using a spotter to monitor application;
• Flag or otherwise identify native or listed plants and use plant guards to protect these plants in the application area; and
• For herbicides, cut or mow target vegetation first and subsequently treat cut stems or resprouting vegetation to reduce potential drift to nontargeted plants.
(7) Inadequate regulatory mechanisms—In addition to the six primary threats identified above, the listing rule and recovery plan identified inadequate regulatory mechanisms or failure to enforce these regulations as a factor affecting the status of all the Mariana Islands species (80 FR 59424 at 59467-59468, October 1, 2015; Service 2023a, p. 23). To date, these mechanisms do not address all of the species in this proposed rule:
• Existing Commonwealth and Territorial laws including Fish, Game, and Endangered Species Act (Public Law 2-51) and the Wildlife Conservation Act (CNMI 1994, entire) within the Sabana Heights and I'Chenchon Bird Sanctuary areas, Mariana Crow Conservation Area, and Sabana Protected Area;
• Memorandum of agreement between the Service's Pacific Islands Fish and Wildlife Office and the CNMI Department of Public Lands, with the Northern Mariana Islands Department of Land and Natural Resources, for the Mariana Crow Conservation Area (Service 2011, entire); and
• Management and action plans including CNMI Forest Action Plan 2020-2030 (CNMI Forestry Division of Agriculture—Department of Lands and Natural Resources (CNMI FDoA 2020, entire), CNMI Wildlife Action Plan 2015-2025 (CNMI Division of Fish and Wildlife 2015a, entire), MAC Plan (MAC Working Group 2014, entire), CNMI Comprehensive Public Land Use Plan Update for Rota, Tinian, Saipan, and the Northern Islands (CNMI Department of Public Lands (CNMI DPL) 2019, entire), and CNMI's Comprehensive Sustainable Development Plan 2021-2030 (CNMI OPD 2021, entire).
Inadequate regulatory mechanisms threaten the Mariana Islands species and their habitats by allowing development that degrades and destroys suitable habitat and allows spread of invasive/nonnative species by not employing biosecurity measures (Service 2023a, p. 23). The laws do not prohibit or address the intentional introduction of ungulates or intentional ignition of wildfires, except for Public Law 35-134, which extends the definition of arson to include destruction or damage to forest lands (Territory of Guam 2020, entire). Local laws in the Territory of Guam and the CNMI have not been updated to include all of the federally endangered and threatened species addressed in this proposed rule. As a result, “take” of endangered or threatened wildlife is not prohibited under local law during development and other activities, nor are endangered or threatened plants considered. This limits protection of these species and their habitats to projects with a Federal nexus (Service 2023a, p. 23). Examples of special management considerations or protection that could address inadequate regulatory mechanisms or failure to enforce these regulations may include (but are not limited to):
• Locally list federally listed species and ensure local laws are updated;
• Encourage the passage and enforcement of laws, ordinances, and codes that protect federally endangered and threatened species and their habitat, where applicable;
• Encourage Territorial and Commonwealth governments to adopt policies that support less development, address biosecurity inadequacies, prevent the intentional introduction of ungulates, and prevent the intentional ignition of wildfires; and
• Employ full-time enforcement officers that can educate the public about regulations and have the power to prosecute violations of local laws, ordinances, and codes.
Criteria Used To Identify Critical Habitat
As required by section 4(b)(2) of the Act, we use the best scientific data available to designate critical habitat. In accordance with the Act and our implementing regulations at 50 CFR 424.12(b), we review available information pertaining to the habitat requirements of the species and identify specific areas within the geographical area occupied by the species at the time of listing and any specific areas outside the geographical area occupied by the species to be considered for designation as critical habitat.
• For 9 animal species (Pacific sheath-tailed bat, Slevin's skink, Mariana eight-spot butterfly, Mariana wandering butterfly, Rota blue damselfly, fragile tree snail, Guam tree snail, humped tree snail, and Langford's tree snail) and 13 plant species (
Bulbophyllum guamense, Cycas micronesica,
Dendrobium guamense, Eugenia bryanii, Hedyotis megalantha,
Heritiera longipetiolata, Maesa walkeri, Nervilia jacksoniae, Phyllanthus saffordii,
Psychotria malaspinae, Tabernaemontana rotensis, Tinospora homosepala,
and
Tuberolabium guamense
), we are proposing to designate critical habitat in areas within the geographical area that these species occupied at the time of listing (see tables 3-24 and descriptions for Areas 1-41, below). We are not proposing to designate any areas outside the geographical area occupied by the species because we have not identified any unoccupied areas that meet the definition of critical habitat. These occupied areas encompass the varying habitat types and distribution of these Mariana Islands species and provide sufficient habitat to allow for maintaining and potentially expanding their distributions, areas of which are essential to the species' conservation.
• For one plant species,
Solanum guamense,
we are not proposing critical habitat because the area that meets the definition of critical habitat is exempt under section 4(a)(3)(B)(i) of the Act (see Exemptions, below). We are also not proposing to designate any areas outside the geographical area occupied by
Solanum guamense
because we have not identified any unoccupied areas that meet the definition of critical habitat. This species was last seen in 1994 on DoD lands within the exempted area, and most other locations with historical records of this species have been developed or converted to unsuitable habitat (Service 2023u, p. i).
• For the Mariana subspecies of the Pacific sheath-tailed bat, we are proposing to designate critical habitat in one location that is within the geographical area occupied by the species at the time of listing (the island of Aguiguan) and also one location that is outside the geographical area occupied by the species at the time of listing (the island of Rota) because we
have determined the unoccupied area is essential for the conservation of the species (see table 2 and descriptions for Areas 9 and 14, below).
The Mariana subspecies of Pacific sheath-tailed bat occurs only on Aguiguan Island, but historically occupied seven islands within the Marianas (Service 2023a, p. 10). The bat is highly susceptible to stochastic and catastrophic events, especially considering the threats it faces, such as depredation by nonnative animals, disturbance at roost caves, and habitat loss from deforestation and overgrazing by ungulates (Service 2023a, pp. 10, 41-43, 63). Therefore, we have determined that the area currently occupied by this subspecies, on Aguiguan, is insufficient to support the species' representation, redundancy, and resiliency. We anticipate that recovery will require continued protection of the existing population and its habitat, and reintroduction of the Mariana subspecies of the Pacific sheath-tailed bat into other areas, ensuring there are adequate numbers of the bats in multiple locations. The delisting criteria specified in the species' recovery plan includes a minimum of six stable or increasing populations with consistently occupied roosts on three or more islands (noting that stable populations have at least 500 individuals over a 10-year period (Service 2023a, pp. 41-43)). Therefore, we have identified three locations necessary to recover the Mariana subspecies of Pacific sheath-tailed bat: the occupied island of Aguiguan (see Proposed Critical Habitat Designation, Area 9, below) and the unoccupied islands of Rota (see Proposed Critical Habitat Designation, Area 14, below) and Guam (on DoD lands that are exempt under section 4(a)(3) (see Exemptions, below)).
The Pacific sheath-tailed bat was historically found on Guam and Rota, and the caves and foraging habitat present on the islands provide the resources (
i.e.,
PBFs) needed by the species. At this time for Guam, the U.S. Department of Defense (DoD) has a contract with the U.S. Geological Survey (USGS) to survey for Pacific sheath-tailed bats using acoustic monitors and cameras in caves on DoD lands that are currently or were historically occupied by the endangered Mariana swiftlet, which is known to co-occur with the Pacific sheath-tailed bat (Duenas 2024, pers. comm.; Lemke 1986, p. 744). This roosting and foraging habitat meets the definition of critical habitat and occurs on DoD lands; therefore, in accordance with section 4(a)(3)(B)(i) of the Act, we have determined that the identified lands on Guam are subject to the Joint Region Marianas (JRM) INRMP and that conservation efforts identified in the JRM INRMP will provide a benefit to the Pacific sheath-tailed bat (see Exemptions, below).
At this time on Rota, communications are underway with CNMI Division of Fish and Wildlife and Biodiversity Research Institute to plan for potential future translocations of Pacific sheath-tailed bat from Aguiguan to Rota (Guilbert et al. 2024, pers. comm.). With the best available scientific information, we identified the unoccupied area on Rota as containing one or more of the PBFs that support the life history requirements of the subspecies and meeting the definition of critical habitat. Designating this unoccupied area as critical habitat for this subspecies also promotes conservation actions to restore the historical, geographical, and ecological representation that is important for its recovery (Service 2023a, p. 42). In general, this species, and others occupying CNMI and Guam, are so rare in the wild that they are at a high risk of extirpation or even extinction from various catastrophic events, such as typhoons. Therefore, supporting resiliency and redundancy for the Pacific sheath-tailed bat through the establishment of multiple, robust populations is a key component of conservation of the species (Service 2023a, p. 42). A designation limited to the single occupied area on Aguiguan is inadequate to ensure the conservation of this subspecies. Areas that may have been unoccupied at the time of listing, together with the area occupied at the time of listing, are reasonably certain to provide some or all of the habitat necessary for the expansion of existing wild populations and reestablishment of wild populations within the historical range of the subspecies to support viability.
For all of the Mariana Islands species addressed in this proposed rule, we evaluated the following information to determine and select appropriate areas occupied at the time of listing that also contain the PBFs essential to the conservation of each species: (1) the 2015 listing rule (80 FR 59424; October 1, 2015), (2) 5-year reviews (Service 2020a-u, entire; Service 2021, entire; Service 2024a-b, entire), (3) species reports (Service 2020t-ao, entire; Service 2023b-x, entire), (4) habitat status assessments (Frager et al. 2019, entire; Plentovich et al. 2020, entire; Polhemus and Richardson 2020, entire; Willsey et al. 2019, entire), (5) the recovery plan for the 23 species in the Marianas (Service 2023a, entire), (6) section 7 consultations and technical assistance requests, (7) multiple published and unpublished reports included in the literature cited section, and (8) our database information relevant to species presence and suitable habitat.
All of the species in this proposed rule had not been thoroughly surveyed prior to the time of listing in 2015, which required our consideration of and reliance on updated species occurrence data from our Federal and local partner agencies. Therefore, to determine if an area was occupied at the time of listing, either: (1) individuals were observed prior to listing; or (2) if surveys were not conducted until after listing, an area was considered occupied if the habitat had not changed since listing and the best available information indicated that the area was likely occupied at the time of listing (
e.g.,
individuals of a species were observed within adjacent and/or connected suitable habitat areas that have no barriers to dispersal). In some of these instances, recent surveys have confirmed individuals within these new areas.
In this proposed rule, we propose critical habitat for 22 species in CNMI and Guam that include 122 critical habitat units. Each proposed critical habitat unit contains all or some of the PBFs essential to the conservation of the species that occupy their respective units. In some instances, limited data sources were available on the species itself or surrogates to provide specificity for features such as food, water quality parameters, nutritional or physiological requirements, reproduction requirements, and the specific amount of space necessary for individual and population growth. Therefore, in some instances we use general descriptions of the PBFs based on the best scientific information available. The proposed critical habitat includes the soil substrate, vegetation, and (if applicable) cave or stream system that supports the life history requirements for each of the species. Some species may require more than one type of substrate and vegetation (
e.g., Cycas micronesica
occurs on volcanic, limestone, or coastal strand substrates, each with the associated forest plant communities typical of their respective substrates).
Because multiple species within this proposed rule have similar life history requirements, the species are grouped together within this preamble based on these related requirements. The eight species groups include:
(1) mammals (1 species—Pacific sheath-tailed bat);
(2) reptiles (1 species—Slevin's skink);
(3) tree snails (4 species—fragile tree snail, Guam tree snail, humped tree snail, and Langford's tree snail);
(4) butterflies (2 species—Mariana eight-spot butterfly, Mariana wandering butterfly);
(5) damselflies (1 species—Rota blue damselfly);
(6) epiphytic orchids (3 species—
Bulbophyllum guamense, Dendrobium guamense,
and
Tuberolabium guamense
);
(7) forest plants (9 species—
Eugenia bryanii, Heritiera longipetiolata, Maesa walkeri, Psychotria malaspinae, Tabernaemontana rotensis, Nervilia jacksoniae, Cycas micronesica,
and
Tinospora homosepala
); this grouping also included our evaluation of information for
Solanum guamense
(see Exemptions, below); and
(8) savanna plants (2 species—
Hedyotis megalantha
and
Phyllanthus saffordii
).
We used similar methods to identify critical habitat unit boundaries for each of the species and species groups. The species groups were considered together because spatial data used for delineating critical habitat are similar among the species in each group, and these species all occur within similar habitat types, such as limestone forests or savannas. When delineating critical habitat, we considered each species separately to determine the respective unit boundaries and subsequently overlapped units to determine if there were shared boundaries to also be able to report the total proposed critical habitat on each island and within geographic locations (
i.e.,
area descriptions). Critical habitat boundaries for all species were delineated to clearly depict and promote conservation of these species by identifying habitats that contain features on which each species depends. For units consisting of multiple habitat types, such as the cave and forest habitats for the Pacific sheath-tailed bat, the proposed critical habitat designation includes the entire suitable habitat area for the species because both habitat types contain the roosting and foraging features essential to the conservation of the species.
To delineate proposed critical habitat units, we relied on a conservation strategy in which each of the species was considered separately using a common approach for each grouping. The goal of the conservation strategy was to identify the specific areas for each species that provide essential PBFs while also taking into account range-wide resiliency, redundancy, and representation (Species Reports) (Service 2020t-ao, entire; Service 2023b-x, entire).
In general, we completed the following four basic steps for each species to delineate critical habitat: (a) We compiled the best scientific data available on observations and distributions of the Mariana Islands species that were extant at the time of listing or assumed extant at the time of listing; (b) we compiled the best available location and landcover data within the range of all the species, including soil substrate, vegetation, elevation, temperature, and precipitation, and identified areas containing the PBFs that may require special management considerations or protection; (c) we circumscribed boundaries of potential critical habitat units based on the above information specific to the resource needs of each species; and (d) we removed, to the extent practicable, areas that did not have the specific PBF components.
In summary, for areas within the geographical area occupied by the species at the time of listing, we delineated critical habitat unit boundaries using the following criteria:
(1)
Obtain and evaluate species observation and distribution data sources
—We obtained and evaluated observation and distribution data to include in our Geographic Information System (GIS) database for each of the species, including our Pacific Islands Fish and Wildlife Office's threatened and endangered species database, which contains current and historical species observation and distribution survey report data from Federal and local partners. We also obtained recent biological surveys and reports and discussed that information with experts familiar with the species and their habitats. We used historical and current species distribution information to understand occupancy at the time of listing and to develop initial critical habitat boundaries within the habitats occupied by each of the species. The initial boundaries were superimposed over digital topographical maps of each of the islands that one or more of the species occupied and further evaluated to (a) remove locations identified as highly degraded or developed, and (b) use natural or constructed features (
e.g.,
ridge lines, valleys, streams, coastlines, roads, etc.) to refine the proposed critical habitat boundaries.
(2)
Identify areas containing PBFs
—Data layers defining map units were created using Environmental Systems Research Institute ArcGIS Pro World Imagery (2021). We obtained and compiled temperature (Fick and Hijmans 2017, entire), precipitation (Fick and Hijmans 2017, entire), elevation (USGS 2013), soil substrate (Guam Bureau of Statistics and Plans 2013, entire; Natural Resources Conservation Service 2019, entire), landcover (Amidon et al. 2017, entire), and cave or stream system data sources for each island within the Mariana archipelago. We evaluated areas to ensure each unit for each species contained one or more of the PBFs essential to the conservation of the species and which may require species management considerations or protection.
Areas that were known to be occupied at the time of listing and containing one or more of the PBFs were evaluated and included as proposed critical habitat. These areas include the contiguous habitat surrounding survey points that were known at the time of listing, all of which contain one of more of the PBFs and where there were no barriers to dispersal (
e.g.,
no changes in landcover from forest to grassland or developed areas since 2015); recent surveys have confirmed occupancy in some of these contiguous habitat areas. We considered the degree to which the PBFs were present or absent in areas as an indication of habitat suitability for each species and removed areas lacking the identified PBFs. Areas within proposed critical habitat units that contained obvious unsuitable habitat (
e.g.,
grasslands, bare rock, agricultural lands) were removed from the unit boundaries because they do not contain one or more of the PBFs needed by the species.
(3)
Circumscribe boundaries of potential critical habitat units
—We considered several features in the selection of specific boundaries for critical habitat units, including occupancy of the area at the time of listing (
i.e.,
consideration of historical and current location data, as described above), the Service's landcover information, and the presence of adequate habitat to allow for increases in numbers of individuals and for the expansion of populations necessary for recovery (Service 2023a, entire). For example, if data layers indicated that substrate and vegetation type were present on small or disjunct parcels within developed communities, these areas were not included as proposed critical habitat. Areas of contiguous suitable habitat were included within a unit boundary if data layers indicated that substrate and vegetation were similar to that of the occupied areas, there were no barriers to dispersal to allow for future population expansion, and the areas contained one or more of the PBFs. Critical habitat boundaries for all species were delineated to promote
the conservation of these species by identifying the PBFs essential to the conservation of each species (
i.e.,
the resources on which each species depends).
(4)
For the unoccupied unit for the Mariana subspecies of Pacific sheath-tailed bat
—For the one unit on the island of Rota for the Mariana subspecies of Pacific sheath-tailed bat, which is outside the geographic area occupied by the subspecies at the time of listing, we delineated critical habitat unit boundaries using the following criteria:
First, we obtained and evaluated the historical observation and distribution data for the subspecies and superimposed the data layers over topographical maps. We identified areas containing the PBFs using information including temperature, precipitation, elevation, soil substrate, land cover, and cave system maps, which we inferred from information known from the occupied unit on Aguiguan. Similar to the occupied unit on Aguiguan, we considered historically occupied areas, the Service's landcover information, and habitat to allow for the expansion of populations. Finally, we removed areas that did not include the PBFs required by the subspecies (
e.g.,
coastlines or bare rock).
Then, to ensure the unit boundary of the unoccupied unit on Rota is based on the best available science, we examined all known sources of relevant information. Many potentially suitable roosting caves occur in southern Rota (Duenas 2024, pers. comm.). Cave system data layers were used to identify suitable bat roosting habitat while the landcover data layer was used to identify suitable foraging habitat (Keel et al. 2005, entire; Taborosi 2006, entire). We considered data on the current or historical locations of the Mariana swiftlet because the species is known to co-locate with the Pacific sheath-tailed bat in the same caves on Aguiguan (Lemke 1986, p. 744; Service 1991, pp. 8, 10-11; Wiles et al. 1997, p. 221). On Rota, the unit boundaries extend 3.1 mi (5 km) around roosting caves within the adjacent forested area to provide adequate adjacent foraging habitat. This distance is based on data from the Pacific sheath-tailed bat subspecies
Emballonura semicaudata palauensis,
a species also co-occurring with a cave-dwelling swiftlet on the island of Palau in the Pacific. The best available information indicates that the
palauensis
subspecies bats flew up to 3.1 mi (5 km) from caves to forage (Wiles et al. 1997, p. 221). Contiguous forested habitat surrounding or very near suitable roosting sites is necessary for the species (the whole of
Emballonura semicaudata
) because they avoid non-forest habitats (Esselstyn et al. 2004, p. 307).
When determining proposed critical habitat boundaries, we made every effort to avoid including developed areas such as lands covered by buildings, pavement, and other structures because such lands lack PBFs necessary for the Mariana Islands species. The scale of the maps we prepared under the parameters for publication within the Code of Federal Regulations may not reflect the exclusion of such developed lands. Any such lands inadvertently left inside critical habitat boundaries shown on the maps of this proposed rule have been excluded by text in the proposed rule and are not proposed for designation as critical habitat. Therefore, if the critical habitat is finalized as proposed, a Federal action involving these lands (and not affecting the designated critical habitat) would not trigger section 7 consultation with respect to critical habitat and the requirement of no adverse modification unless the specific action would affect the PBFs in the adjacent critical habitat.
The proposed critical habitat designation is defined by the map or maps, as modified by any accompanying regulatory text, presented at the end of this document under Proposed Regulation Promulgation.
Proposed Critical Habitat Designation
We are proposing approximately 59,886 ac (24,235 ha) as critical habitat in 41 distinct geographic areas that include 122 critical habitat units for 22 Mariana Islands species, including 9 animals (the Mariana subspecies of the Pacific sheath-tailed bat, Slevin's skink, fragile tree snail, Guam tree snail, humped tree snail, Langford's tree snail, Mariana eight-spot butterfly, Mariana wandering butterfly, and Rota blue damselfly) and 13 plants (
Bulbophyllum guamense, Cycas micronesica, Dendrobium guamense, Eugenia bryanii, Hedyotis megalantha, Heritiera longipetiolata, Maesa walkeri, Nervilia jacksoniae, Phyllanthus saffordii, Psychotria malaspinae, Tabernaemontana rotensis, Tinospora homosepala,
and
Tuberolabium guamense
). Critical habitat is not proposed for one plant,
Solanum guamense,
because we have determined that the area identified that meets the definition of critical habitat is exempt from designation under section 4(a)(3)(B) of the Act (see Exemptions, below). The critical habitat areas we describe below constitute our current best assessment of areas that meet the definition of critical habitat for each species. The 122 units we propose as critical habitat are presented in the following tables for each species. All units are occupied with the exception of one unit on the island of Rota for the Pacific sheath-tailed bat. A second unit for the Pacific sheath-tailed bat that was identified on Guam meets the definition of critical habitat but is exempt from critical habitat designation under section 4(a)(3)(B) of the Act (see Exemptions, below). Many of the units and acreage for a given species overlap in part or whole with units for other species in this proposed rule on most of the islands; additional overlap with existing critical habitat designations also occurs on the Islands of Rota and Guam. The landownership in many (but not all) of the proposed critical habitat units also include a category called “uncategorized lands.” For the purposes of this analysis and the proposed critical habitat designation, this category refers to lands where we were unable to determine local government or private ownership.
To ensure clarity for the public and landowners managing for multiple species in a given area, Table 2 identifies the 41 individual areas across CNMI and the Territory of Guam, as well as all species with proposed critical habitat units in each of those areas. Table 3 identifies the total number of areas, species, and acreage proposed as critical habitat on each island. Tables 4-26 show the proposed critical habitat units, land ownership, acreage size, and occupancy status for each of the 22 species. Unit names correspond to the specific species and island where they occur, with additional numbers or letters corresponding to the locations/areas, thereby providing the ability to cross reference to situations with overlapping units.
The islands of Asuncion, Pagan, Alamagan, Sarigan, Saipan, Tinian, and Aguiguan do not have any existing designated critical habitat; thus, there is no overlapping designated critical habitat on these islands and all proposed critical habitat in this rule is new to these islands. On the islands of Rota (Areas 10-14) and Guam (Areas 15-41), there are existing designated critical habitat units that overlap with critical habitat proposed in this rule. For Rota, this proposed rule includes 13,023 ac (5,270 ha) of proposed critical habitat for 13 of the 22 Mariana Islands species (Table 3), of which 63 percent (8,244 ac (3,336 ha)) overlap with existing critical habitat; thus, 37 percent (4,779 ac (1,934 ha)) of proposed critical habitat is new to this island. For Guam (which
includes Cocos Island), this proposed rule includes 36,473 ac (14,760 ha) of proposed critical habitat for 19 of the 22 Mariana Islands species (Table 3), of which 0.7 percent (257 ac (104 ha)) overlap with existing critical habitat; thus, 99 percent (36,216 ac (14,656 ha)) of proposed critical habitat is new to this island.
Table 2—Proposed Critical Habitat for Each of the 41 Areas and the Species Represented Within Each Area
[Area estimates reflect the total proposed critical habitat acres within each geographical area. The total acreage for each area does not double-count any acres of overlapping units, where applicable.]
Geographic area
Species represented
Total proposed critical habitat in acres
(hectares)
Area 1—Asunción, CNMI
Slevin's skink
750 (304)
Area 2—Pagan, CNMI
Slevin's skink
humped tree snail.
1,846 (747)
Area 3—Alamagan, CNMI
Slevin's skink
humped tree snail.
1,420 (574)
Area 4—Sarigan, CNMI
Slevin's skink
humped tree snail.
402 (163)
Area 5—Tapochau, Saipan, CNMI
humped tree snail
3,290 (1,332)
Area 6—American Memorial Park, Saipan, CNMI
humped tree snail
35 (14)
Area 7—I'Naftan, Saipan, CNMI
Heritiera longipetiolata
779 (315)
Area 8—Kastiyu, Tinian, CNMI
Heritiera longipetiolata
651 (263)
Area 9—Aguiguan, CNMI
Pacific sheath-tailed bat
Langford's tree snail.
Dendrobium guamense.
1,217 (492)
Area 10—Mochong, Rota, CNMI
Bulbophyllum guamense
Tabernaemontana rotensis.
* 3,497 (1,415)
Area 11—Sabana, Rota, CNMI
Bulbophyllum guamense
Cycas micronesica.
Dendrobium guamense.
* 6,875 (2,782)
Maesa walkeri
Nervilia jacksoniae
Tabernaemontana rotensis
Tuberolabium guamense
Area 12—Rota, CNMI
fragile tree snail
humped tree snail.
Mariana wandering butterfly.
12,282 (4,970)
Area 13—Talakhaya, Rota, CNMI
Rota blue damselfly
1,133 (459)
Area 14—Southern Rota, CNMI
Pacific sheath-tailed bat
*
+
7,632 (3,089)
Area 15—Ritidian, Guam
fragile tree snail
Guam tree snail.
humped tree snail.
Mariana eight-spot butterfly.
856 (346)
Bulbophyllum guamense
Cycas micronesica
Dendrobium guamense
Eugenia bryanii
Heritiera longipetiolata
Tabernaemontana rotensis
Tuberolabium guamense
Area 16—Two Lovers' Point, Guam
fragile tree snail
Guam tree snail.
humped tree snail.
1,245 (504)
Mariana eight-spot butterfly
Bulbophyllum guamense
Cycas micronesica
Dendrobium guamense
Eugenia bryanii
Heritiera longipetiolata
Tabernaemontana rotensis
Tuberolabium guamense
Area 17—Anao, Guam
fragile tree snail
Guam tree snail.
humped tree snail.
2,166 (877)
Mariana eight-spot butterfly
Bulbophyllum guamense
Cycas micronesica
Dendrobium guamense
Eugenia bryanii
Heritiera longipetiolata
Psychotria malaspinae
Tabernaemontana rotensis
Tuberolabium guamense
Area 18—Tre Vista, Guam
fragile tree snail
Guam tree snail.
445 (180)
Area 19—Yigo, Guam
Guam tree snail
147 (59)
Area 20—Barrigada, Guam
Guam tree snail
Bulbophyllum guamense.
267 (108)
Area 21—Taguan, Guam
Mariana eight-spot butterfly
242 (98)
Area 22—Anigua Cliffline, Guam
Tinospora homosepala
11 (5)
Area 23—Asan Ridge, Guam
Tinospora homosepala
12 (5)
Area 24—Asan Hillside, Guam
Tinospora homosepala
** 124 (50)
Area 25—Nimitz Hill Savanna, Guam
Phyllanthus saffordii
236 (95)
Area 26—Piti Savanna, Guam
Phyllanthus saffordii
82 (33)
Area 27—Sasa Valley, Guam
Tinospora
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