Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Peninsular Bighorn Sheep (Ovis canadensis nelsoni), 57740-57780 [07-4959]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 72, Number 195 (Wednesday, October 10, 2007)]
[Proposed Rules]
[Pages 57740-57780]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 07-4959]



[[Page 57739]]

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Part III





Department of the Interior





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Fish and Wildlife Service



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50 CFR Part 17



 Endangered and Threatened Wildlife and Plants; Designation of Critical 
Habitat for the Peninsular Bighorn Sheep (Ovis canadensis nelsoni) and 
Proposed Taxonomic Revision; Proposed Rule

Federal Register / Vol. 72, No. 195 / Wednesday, October 10, 2007 / 
Proposed Rules

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AV09


Endangered and Threatened Wildlife and Plants; Designation of 
Critical Habitat for the Peninsular Bighorn Sheep (Ovis canadensis 
nelsoni) and Proposed Taxonomic Revision

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Proposed rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), propose to 
revise currently designated critical habitat for the Peninsular bighorn 
sheep (Ovis canadensis nelsoni) under the Endangered Species Act of 
1973, as amended (Act). In total, approximately 384,410 acres (ac) 
(155,564 hectares (ha)) of land in Riverside, San Diego, and Imperial 
counties, California, fall within the boundaries of the proposed 
revised critical habitat designation. Of the area proposed as revised 
critical habitat, approximately 4,512 ac (1,826 ha) of land are Tribal; 
93,720 ac (37,927 ha) are Federal; 249,840 ac (101,107 ha) are State; 
35,824 ac (14,497 ha) are private; and 514 ac (208 ha) are local. We 
are proposing to exclude from the final designation, under section 
4(b)(2) of the Act, approximately 4,512 ac (1,826 ha) of Agua Caliente 
Band of Cahuilla Indians Tribal land. We are also evaluating and 
considering the possible exclusion of approximately 19,211 ac (7,774 
ha) of private land covered under the draft Coachella Valley Multiple 
Species Habitat Conservation Plan. Further, we are acknowledging a 
taxonomic change to the species and are proposing a taxonomic revision 
of the listed entity from distinct population segment (DPS) of species 
Ovis canadensis, to DPS of subspecies Ovis canadensis nelsoni.

DATES: We will accept comments from all interested parties until 
December 10, 2007. We must receive requests for public hearings, in 
writing, at the address shown in the ADDRESSES section by November 26, 
2007.

ADDRESSES: If you wish to comment on this proposed rule, you may submit 
your comments and materials concerning by any one of several methods:
    1. By mail or hand-delivery to: Jim Bartel, Field Supervisor, U.S. 
Fish and Wildlife Service, Carlsbad Fish and Wildlife Office, 6010 
Hidden Valley Road, Carlsbad, CA 92011.
    2. By electronic mail (e-mail) to: fw8cfwocomments@fws.gov. Please 
see the Public Comments Solicited section below for other information 
about electronic filing.
    3. By fax to: the attention of Jim Bartel at 760-431-5901.
    4. Via the Federal eRulemaking Portal at: https://
www.regulations.gov. Follow the instructions for submitting comments.

FOR FURTHER INFORMATION CONTACT: Jim Bartel, Field Supervisor, Carlsbad 
Fish and Wildlife Office, 6010 Hidden Valley Road, Carlsbad, CA 92011; 
telephone 760-431-9440 ; facsimile 760-431-5901. If you use a 
telecommunications device for the deaf (TDD), call the Federal 
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION:

Public Comments

    We intend that any final action resulting from this proposal to 
revise the current critical habitat designation for the Peninsular 
bighorn sheep will be as accurate and as effective as possible. 
Therefore, we request comments or suggestions on this proposed rule. We 
particularly seek comments concerning:
    (1) The reasons why we should or should not designate habitat as 
``critical habitat'' under section 4 of the Act (16 U.S.C. 1531 et 
seq.), including whether there are threats to the subspecies from human 
activity, the degree of which can be expected to increase due to the 
designation, that outweigh the benefit of designation, such that the 
designation of critical habitat is not prudent, and whether there are 
areas we previously designated, but are not proposing for revised 
designation here, that should be designated as critical habitat;
    (2) Specific information on the amount and distribution of 
Peninsular bighorn sheep habitat, what areas occupied at the time of 
listing and that contain features essential for the conservation of the 
subspecies we should include in the designation and why, and what areas 
not occupied at the time of listing are essential for the conservation 
of the subspecies and why;
    (3) The appropriateness of the proposed exclusion of approximately 
4,512 ac (1,826 ha) of Peninsular bighorn sheep habitat from the final 
designation in consideration of Secretarial Order 3206, ``American 
Indian Tribal Rights, Federal Tribal Trust Responsibilities, and the 
Endangered Species Act'' (June 5, 1997); the President's memorandum of 
April 29, 1994, ``Government-to-Government Relations with Native 
American Tribal Governments'' (59 FR 22951); Executive Order 13175; and 
the relevant provision of the Departmental Manual of the Department of 
the Interior (512 DM 2) (see ``Proposed Exclusion of Agua Caliente Band 
of Cahuilla Indians Tribal Lands Under Section 4(b)(2) of the Act'' for 
a detailed discussion); specifically any additional information 
regarding the benefits of including these Tribal lands in the 
designation or of excluding these lands from the designation;
    (4) The appropriateness of the possible exclusion of approximately 
19,211 acres (ac) (7,774 hectares (ha)) of Peninsular bighorn sheep 
habitat from the final designation based on the benefits to the 
conservation of the subspecies and its PCEs provided by the draft 
Coachella Valley Multiple Species Habitat Conservation Plan (MSHCP) 
(see ``Areas Considered for Exclusion Under Section 4(b)(2) of the 
Act'' for a detailed discussion), specifically any additional 
information on the benefits of including land covered by the draft 
Coachella Valley Multiple Species Habitat Conservation Plan in the 
designation or of excluding these lands from the designation. At this 
time we are only considering private lands under the draft Coachella 
Valley MSHCP for exclusion and soliciting comment on the 
appropriateness of excluding California Department of Fish and Game, 
and Bureau of Land Management lands as Memorandum of Understanding 
partners to the MSHCP;
    (5) Land use designations and current or planned activities in the 
subject areas and their possible impacts on proposed revised critical 
habitat;
    (6) Any foreseeable economic, national security, or other potential 
impacts resulting from the proposed revised designation and, in 
particular, any impacts on small entities, and the benefits of 
including or excluding areas that exhibit these impacts; and
    (7) 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.
    You may submit your comments and materials concerning this proposal 
by one of several methods (see ADDRESSES). If you use e-mail to submit 
your comments, please include ``Attn: Peninsular bighorn sheep'' in 
your e-mail subject header, preferably with your name and return 
address in the body of your message. If you do not receive a 
confirmation from the system that we have received your e-mail, contact 
us directly by calling our Carlsbad Fish and Wildlife Office at 760-
431-9440. Please note that we must

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receive comments by the date specified in the DATES section in order to 
consider them in our final determination.
    Before including your address, phone number, e-mail address, or 
other personal identifying information in your comment, you should be 
aware that your entire comment--including your personal identifying 
information--may be made publicly available at any time. While you may 
ask us in your comment to withhold your personal identifying 
information from public review, we cannot guarantee that we will be 
able to do so.
    Comments and materials we receive, as well as supporting 
documentation we used in the preparation of this proposed rule, will be 
available for public inspection, by appointment, during normal business 
hours at the Carlsbad Fish and Wildlife Office, 6010 Hidden Valley 
Road, Carlsbad, CA 92011 (telephone 760-431-9440).

Background

    In this proposed rule, it is our intent to discuss only those 
topics directly relevant to the revision of designated critical habitat 
for the Peninsular bighorn sheep and the proposed taxonomic revision of 
the current listed entity. For more information on the biology, and 
ecology of the Peninsular bighorn sheep, refer to the final listing 
rule published in the Federal Register on March 18, 1998 (63 FR 13134), 
and the proposed and final critical habitat rules published in the 
Federal Register on July 5, 2000, and February 1, 2001, respectively 
(65 FR 41405 and 66 FR 8650).
    In the 1998 final listing rule, Peninsular bighorn sheep were 
listed as a distinct population segment (DPS) of the species Ovis 
canadensis. As stated in the 2001 critical habitat rule, based on 
morphometric and genetic analysis, Wehausen and Ramey (1993, p. 9) 
synonymized Peninsular bighorn sheep with the subspecies nelsoni, which 
is the current taxonomy. Although we accepted this taxonomy at the time 
of the designation in 2001, we have yet to formally revise the taxonomy 
of the listed entity. Therefore, we are formally proposing a taxonomic 
revision to amend the final listing rule from a DPS of the species Ovis 
canadensis, to a DPS of the subspecies Ovis canadensis nelsoni. 
Therefore, within this proposed critical habitat rule we will refer to 
the listed entity as a subspecies and not a species. The taxonomic 
revision does not materially affect discreteness and significance of 
the Peninsular bighorn sheep as a DPS entity. As stated in the final 
listing rule (63 FR 13134), regardless of taxonomic issues surrounding 
this species at the time of listing, the biological evidence supports 
recognition of Peninsular bighorn sheep as a distinct vertebrate 
population segment in the Service's Recognition of Distinct Vertebrate 
Population Segments (DPS) (61 FR 4722). For a detailed discussion of 
the DPS analysis for Peninsular bighorn sheep, see the Distinct 
Vertebrate Population Segment section of the final listing rule.
    Peninsular bighorn sheep (a large mammal in the family Bovidae) 
occupying the Peninsular Ranges of southern California were determined, 
at the time of listing in 1998, to be a distinct vertebrate population 
segment (DPS) of bighorn sheep based on their geographic isolation and 
separation from other desert bighorn sheep (63 FR 13134; March 18, 
1998). Peninsular bighorn sheep occur on moderate to steep (greater 
than 20 percent) (NRCS 1993, p. 66) open slopes, canyons, and washes in 
hot and dry desert regions of the Peninsular Ranges of southern 
California in Riverside, San Diego, and Imperial counties (66 FR 8650; 
February 1, 2001). Peninsular bighorn sheep use several different 
habitat types, elevations, and slopes depending on seasonal 
environmental conditions and/or their life history stage. The 2001 
final critical habitat rule (66 FR 8650) stated that most Peninsular 
bighorn sheep live between 300 and 4,000 feet (ft) (91 and 1,219 meters 
(m)) in elevation. Upon review of available literature, we now believe 
4,600 ft (1,400 m) (below forested vegetation) is a more widely 
accepted upper elevational limit in the Peninsular Ranges (Jorgensen 
and Turner 1975, p. 51; DeForge et al. 1997, p. 11; Rubin et al. 1998, 
p. 541; Ernest et al. 2002, p. 76). Desert bighorn sheep are frequently 
found on slopes greater than 20 percent (Elenowitz 1983, p. 87; Andrew 
and Bleich 1999, p. 13; Dunn 1996, p. 5), and our Geographic 
Information System (GIS) records and occurrence data confirm this 
observation for Peninsular bighorn sheep. Steep terrains with slopes of 
60 percent or greater used for predator evasion and lambing are a 
crucial component of Peninsular bighorn sheep habitat (Dunn 1996, p. 1; 
Service 2000, p. 6). Peninsular bighorn sheep will use caves and rock 
outcrops for shelter during inclement weather and for shade during 
summer months. Bighorn sheep are primarily diurnal (Krausman et al. 
1985, p. 25), but Peninsular bighorn sheep may be active at any time of 
day or night (Miller et al. 1984, p. 24). A wide range of forage 
resources and vegetation associations are required by this subspecies 
to meet annual and drought-related variations in forage quality and 
availability. In a study of Peninsular bighorn sheep, Scott (1986, p. 
21) found that diets were dominated by shrub species, while grasses and 
forbs species made up a smaller portion of the Peninsular bighorn 
sheep's diet depending on the season. Valley floors, rolling hills, and 
alluvial fans and washes with productive soils provide seasonal 
vegetation and water resources important to the Peninsular bighorn 
sheep, especially for ewes during the reproductive season (Service 
2000, p. 8). Please see the ``Primary Constituent Elements'' section of 
this proposed rule for a detailed discussion of the habitat 
requirements of this subspecies.
    At the time of listing (1998), Peninsular bighorn sheep were known 
to occupy habitat along the Peninsular Mountain Ranges from the San 
Jacinto Mountains of southern California into the Volcan Tres Virgenes 
Mountains in Baja California, Mexico (63 FR 13134; March 18, 1998). 
Population estimates at the time indicated approximately 280 Peninsular 
bighorn sheep existed within the United States, divided amongst 
approximately 8 subpopulations or ewe groups (63 FR 13134; March 18, 
1998). At the time of the final critical habitat designation in 2001, a 
range-wide census estimated approximately 400 Peninsular bighorn sheep 
existed within the United States (Torres 2000, p. 1). We have extensive 
occurrence data documenting bighorn sheep within the entire range 
identified in the listing rule. Population estimates for 2006, derived 
from data collected by the Bighorn Institute, California Department of 
Fish and Game (CDFG), and Anza Borrego Desert State Park, indicate 
approximately 793 adult and yearling Peninsular bighorn sheep exist 
within the United States (Torres 2007). Population estimates for 
various regions within the Peninsular Ranges in 2006 are as follows: 
San Jacinto Mountains, 21; North Santa Rosa Mountains, 49; Central 
Santa Rosa Mountains, 163; South Santa Rosa Mountains, 179; Coyote 
Canyon, 42; North San Ysidro Mountains, 79; South San Ysidro Mountains, 
38; Vallecito and Fish Creek Mountains, 77; and Carrizo Canyon, 145 
(Torres 2007).
    A captive breeding program has been maintained by the Bighorn 
Institute since 1984 in cooperation with CDFG, the Bureau of Land 
Management (BLM), and the Service (Ostermann et al. 2001, p. 751). 
Originally instituted to conduct disease research on low lamb survival, 
the captive breeding program was formalized in 1995, with the goals of 
safeguarding a sample of the Peninsular bighorn sheep gene pool and

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augmenting and reestablishing wild populations (Ostermann et al. 2001, 
p. 751). Captive-bred Peninsular bighorn sheep have been released in 
the northern Santa Rosa Mountains and the San Jacinto Mountains 
(Ostermann et al. 2001, p. 751), areas historically occupied by the 
subspecies.
    Within the Peninsular Ranges, habitat is patchy, and the sheep 
populations are naturally fragmented (Bleich et al. 1990, p. 386; Rubin 
et al. 1998, p. 547). Male and female bighorn sheep remain loosely 
segregated much of the year and come together during the breeding 
period or rut (Bleich et al. 1997, p. 7). In the Peninsular Ranges, the 
rut occurs in the late summer and fall months (Service 2000, p. 15), 
peaking from August to October (Rubin et al. 2000, p. 774). As 
parturition (giving birth) approaches, ewes seek isolated sites (escape 
terrain) with shelter and unobstructed views (Turner and Hansen 1980, 
p. 148), seclude themselves from other females, and find sites to give 
birth (Geist 1971, p. 239; Etchberger and Krausman 1999, p. 358). Ewes 
usually give birth to one lamb after an approximately 6-month gestation 
period (Geist 1971, p. 239; Turner and Hansen 1980, p. 146). During the 
period of sexual segregation, ewes and their lambs are typically found 
in steeper, more secure habitat, while rams inhabit less steep or less 
rugged terrain (Geist 1971, p. 239; Bleich et al. 1997, p. 23).

Previous Federal Actions

    On February 1, 2001, we designated approximately 844,897 ac 
(341,919 ha) of land in Riverside, San Diego, and Imperial counties, 
California, as critical habitat. The designation followed the Service's 
release of the final Recovery Plan for Bighorn Sheep in the Peninsular 
Ranges, California (dated October 25, 2000). On March 7, 2005, the Agua 
Caliente Band of Cahuilla Indians filed a complaint against the Service 
alleging that the economic analysis developed for our 2001 designation 
used a methodology similar to that ruled to be insufficient by the 
Tenth Circuit Court in New Mexico Cattle Growers Association v. U.S. 
Fish and Wildlife Service, 248 F.3d 1277 (10th Cir. 2001). Other 
parties subsequently intervened as plaintiffs in the case. A July 31, 
2006, court-approved consent decree enacted a limited partial vacatur 
of Tribal, mining, and Desert Riders lands (29,925 ac (12,110 ha)) and 
remanded the critical habitat designation back to the Service for new 
rulemaking. Publication of this proposed revision of critical habitat 
satisfies our obligation under the consent decree to submit a revised 
proposed rule to the Federal Register on or before September 30, 2007. 
The final rule is due to the Federal Register on or before September 
30, 2008. For more information on previous Federal actions concerning 
the Peninsular bighorn sheep, refer to the final listing rule published 
in the Federal Register on March 18, 1998 (63 FR 13134), and the 
designation of critical habitat for the Peninsular bighorn sheep 
published in the Federal Register on February 1, 2001 (66 FR 8650).

Critical Habitat

    Critical habitat is defined in section 3 of the Act as:
    (1) The specific areas within the geographical area occupied by a 
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) That may require special management considerations or 
protection; and
    (2) Specific areas outside the geographical area occupied by a 
species at the time it is listed, upon a determination that such areas 
are essential for the conservation of the species.
    Conservation, as defined under section 3 of the Act, means the use 
of all methods and procedures that are necessary to bring any 
endangered species or threatened species to the point at which the 
measures provided under the Act are no longer necessary.
    Critical habitat receives protection under section 7 of the Act 
through the prohibition against Federal agencies carrying out, funding, 
or authorizing the destruction or adverse modification of critical 
habitat. Section 7(a)(2) of the Act requires consultation on Federal 
actions that may affect 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 does not allow the government or public to access private 
lands. Such designation does not require implementation of restoration, 
recovery, or enhancement measures by the landowner. Where the landowner 
seeks or requests federal agency funding or authorization that may 
affect a listed species or critical habitat, the consultation 
requirements of Section 7(a)(2) would apply, but even in the event of a 
destruction or adverse modification finding, the landowner's obligation 
is not to restore or recover the species, but to implement reasonable 
and prudent alternatives to avoid destruction or adverse modification 
of critical habitat.
    For inclusion in a critical habitat designation, habitat within the 
geographical area occupied by the species at the time it was listed 
must first have features that are essential to the conservation of the 
species. Critical habitat designations identify, to the extent known 
using the best scientific data available, habitat areas that provide 
essential life cycle needs of the species (areas on which are found the 
primary constituent elements, as defined at 50 CFR 424.12(b)).
    Occupied habitat that contains the features essential to the 
conservation of the species meets the definition of critical habitat 
only if its essential features may require special management 
considerations or protection.
    Under the Act, we can designate unoccupied areas as critical 
habitat only when we determine that the best available scientific data 
demonstrate that the designation of that area is essential to the 
conservation needs of the species.
    Section 4 of the Act requires that we designate critical habitat on 
the basis of the best scientific and commercial 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 proposed as critical 
habitat, our primary source of information is generally the information 
developed during the listing process for the species. Additional 
information sources may include 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, or other unpublished materials and expert opinion or 
personal knowledge.
    Habitat is often dynamic, and species may move from one area to 
another over time. Furthermore, we recognize that

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designation of critical habitat may not include all of the habitat 
areas that we may eventually determine, based on scientific data not 
now available to the Service, 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 required for recovery of the species.
    Areas that support populations, but are outside the critical 
habitat designation, will continue to be subject to conservation 
actions we implement under section 7(a)(1) of the Act. They are also 
subject to the regulatory protections afforded by the section 7(a)(2) 
jeopardy standard, as determined on the basis of the best available 
scientific information at the time of the agency action. Federally 
funded or permitted projects affecting listed species outside their 
designated critical habitat areas may still result in jeopardy findings 
in some cases. Similarly, critical habitat designations made on the 
basis of the best available information 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 to these planning efforts 
calls for a different outcome.

Methods

    As required by section 4(b) of the Act, we used the best scientific 
data available in determining areas occupied at the time of listing 
that contain the features essential to the conservation of the 
Peninsular bighorn sheep, and areas unoccupied at the time of listing 
that are essential to the conservation of the Peninsular bighorn sheep, 
or both. Material reviewed included information from the final listing 
rule (63 FR 13134; March 18, 1998) and final critical habitat rule (66 
FR 8650; February 1, 2001), information and survey observations 
published in peer-reviewed literature and provided in academic theses 
and agency reports; location data and survey information provided in 
agency status and monitoring reports and on GIS maps; habitat analysis 
and other information provided in the Peninsular bighorn sheep recovery 
plan (Service 2000); material submitted during section 7 consultations; 
data made available through members of the Peninsular Bighorn Sheep 
Recovery Team, Coachella Valley Multiple Species Habitat Conservation 
Plan program, and Agua Caliente Band of Cahuilla Indians Tribal Habitat 
Conservation Plan program; and regional GIS coverages. We are not 
proposing any areas outside the geographical area presently occupied by 
the Peninsular bighorn sheep as revised critical habitat because 
presently occupied areas are sufficient for the conservation of the 
subspecies.

Primary Constituent Elements

    In accordance with section 3(5)(A)(i) of the Act and the 
regulations at 50 CFR 424.12, in determining which areas occupied at 
the time of listing to propose as critical habitat, we consider the 
primary constituent elements (PCEs) to be those physical and biological 
features that are essential to the conservation of the species and that 
may require special management considerations or protection. These 
include, but are not limited to:
    (1) Space for individual and population growth and for normal 
behavior;
    (2) Food, water, air, light, minerals, or other nutritional or 
physiological requirements;
    (3) Cover or shelter;
    (4) Sites for breeding, reproduction, or rearing (or development) 
of offspring; and
    (5) Habitats that are protected from disturbance or are 
representative of the historic geographical and ecological 
distributions of a species.
    We derive the specific primary constituent elements (PCEs) required 
for the Peninsular bighorn sheep from its biological needs.

Space for Individual and Population Growth and for Normal Behavior

    Peninsular bighorn sheep occur on moderately steep to very steep 
open slopes, canyons, and washes in hot and dry desert regions where 
the land is rough and rocky, and sparsely vegetated (66 FR 8650; 
February 1, 2001). This subspecies is primarily restricted to the east-
facing lower elevation slopes (generally below 4,600 ft (1,400 m)) of 
the Peninsular Ranges along the northwestern edge of the Sonoran Desert 
(Jorgensen and Turner 1975, p. 51; DeForge et al. 1997, p. 11; Rubin et 
al. 1998, p. 541; Ernest et al. 2002, p. 76). A wide range of 
topography provides a diversity of habitats and plant communities 
across the mountainous slopes, canyons, washes, and alluvial fans 
within the home range of the Peninsular bighorn sheep (Service 2000, p. 
156). This diverse topography is necessary to provide shelter from the 
elements and predators, areas for rearing, areas used to meet thermal 
requirements, seasonal water and forage sources, and space for mating 
and movement of this subspecies.
    Diverse topographic features are especially important because of 
the extreme temperatures Peninsular bighorn sheep must cope with in 
this desert region. During hot weather, desert bighorn sheep seek shade 
under boulders and cliffs, or move to north-facing slopes (Merritt 
1974, p. 14; Andrew 1994, p. 52). In the event of inclement weather 
they may seek protected caves or overhangs, or move to sunny, south-
facing slopes (Andrew 1994, p. 52), or slopes that are protected from 
strong winds. According to GIS data and occurrence records, Peninsular 
bighorn sheep largely utilize habitat with 20 to 60 percent slopes, 
broken by canyons and washes. The preference for slopes greater than 20 
percent has been shown in other populations of desert sheep as well 
(Andrew 1994, p. 53). Nighttime bedding areas are chosen carefully 
according to the topography of the habitat and may be considered a 
limiting factor in bighorn sheep distribution (Hansen 1980, p. 78). 
These bedding areas are usually located along ridges and spurs with 
long distance visibility where bighorn sheep can escape if necessary in 
a matter of seconds (Hansen 1980, p. 78).
    Generally, bighorn sheep primarily rely on their sense of sight to 
detect predators. They prefer the lower elevations of the Peninsular 
Ranges where the vegetation associations are less dense and provide 
better visibility than those at higher elevations. Research has shown 
that bighorn sheep will avoid habitat in which dense vegetation reduces 
visibility and regularly use habitat with vegetative canopy cover less 
than or equal to 30 percent (Risenhoover and Bailey 1985, p. 799; 
Etchberger et al. 1989, p. 906; Dunn 1996, p. 1). Bighorn sheep in the 
Peninsular Ranges avoid higher elevations (above 4,600 ft (1,400 m)), 
likely due to decreased visibility (and therefore increased predation 
risk) associated with the denser vegetation (chaparral and conifer 
woodland) found at higher elevations (Service 2000, p. 10).
    Along with occupying open habitat, bighorn sheep also use very 
steep, precipitous terrain for predator evasion (Service 2000, p. 6). 
Bighorn sheep use their climbing abilities rather than speed to escape 
from predators, and mountainous slopes of greater than or equal to 60 
percent (escape habitat) are steep enough to provide this function 
(Andrew 1994, p. 57; Dunn 1996, p. 1; McKinney et al. 2003, p. 1231; 
Service 2000, p. 6). Very steep escape habitat is also used for lambing 
(Service 2000, p. 6). As parturition approaches, ewes seek isolated 
sites (escape terrain with slopes

[[Page 57744]]

60 percent or greater) with shelter and unobstructed views (Turner and 
Hansen 1980, p. 148), and seclude themselves from other females while 
finding sites to give birth (Geist 1971, p. 239; Etchberger and 
Krausman 1999, p. 358). Ewes usually give birth to one lamb born after 
an approximately 6-month gestation period (Geist 1971, p. 239; Turner 
and Hansen 1980, p. 146). These areas of steep and very steep terrain 
are vital to Peninsular bighorn sheep because lambs have increased 
vulnerability to predation, and these protective slopes are rarely 
visited by predators (Geist 1971, p. 239). Ewe groups with lambs 
usually stay close to escape terrain, while feeding on lower gradient 
slopes. Berger (1991, p. 72) reported that when feeding on bajadas 
(compound alluvial fans) or away from escape terrain, ewes and lambs 
were more than three times more vulnerable to predation. Predators of 
Peninsular bighorn sheep include mountain lion, bobcat, and coyote 
(Hayes et al. 2000, p. 954; 66 FR 8650).

Metapopulation Structure

    Within desert mountain ranges like the Peninsular Ranges, bighorn 
sheep habitat is patchy, and the population structure is naturally 
fragmented (Bleich et al. 1990, p. 384). This fragmentation has led to 
the application of a broad landscape approach to their population 
ecology, grouping geographically distinct herds into metapopulations, 
which are networks of interacting ewe groups or subpopulations 
(Schwartz et al. 1986, pp. 182-183; Bleich et al. 1990, p. 386). This 
approach considers long-term viability not of individual 
subpopulations, but rather of entire metapopulations; thus both genetic 
and demographic factors are considered. Decreasing population sizes can 
lead to decreasing levels of heterozygosity that may have negative 
demographic effects through inbreeding depression (Lande 1988, p. 
1,456) and loss of adaptability. A small amount of genetic exchange 
among herds by movements of males can counteract inbreeding and 
associated increases in homozygosity that might otherwise develop 
within small, isolated populations (Schwartz et al. 1986, p. 185). 
Males have larger home ranges and have a much greater tendency than 
females to explore new areas, which they may do in search of females 
during the mating season. If geographic distances between female groups 
within metapopulations are not extreme (greater than 31 miles (mi) 50 
kilometers (km) (Witham and Smith 1979, p. 24)), and no insurmountable 
barriers exist, movement by males occurs readily. If movement is 
precluded by human-constructed obstacles, populations will become 
isolated and the metapopulation structure dismantled.
    A study of Peninsular bighorn sheep distribution and abundance by 
Rubin et al. (1998, p. 545) concluded that ewes exhibit a fragmented 
distribution within the Peninsular Ranges making up at least eight ewe 
groups or subpopulations. It is suggested that although the 
distribution of these ewe groups could be considered naturally 
fragmented, construction and use of roads through bighorn sheep habitat 
may have increased fragmentation within the Peninsular Ranges because 
ewes avoided crossing highways (Rubin et al. 1998, p. 547). Ewes show 
strong gregarious and philopatric behavior (faithful to natal home 
range), which limits their dispersal abilities (Boyce et al. 1999, p. 
99; Service 2000, p. 10). Movement of ewes between ewe groups appears 
infrequent, but direct observation and aerial-telemetry locations and 
genetic analysis revealed ram movement between up to three ewe groups 
(Boyce et al. 1999, p. 99; Rubin et al. 1998, pp. 543-544). 
Substructuring also can occur within single herds (ewe groups) of 
bighorn sheep (Festa-Bianchet 1986, pp. 327-330; Andrew et al. 1997, 
pp. 74-75; Rubin et al. 1998, pp. 543-548). Such substructuring is 
defined by separate home range patterns. Although demonstrated more 
with females, it can occur in both sexes.
    Another important long-term process in metapopulation dynamics is 
the balance between rates of natural extinction and colonization among 
subpopulations. Colonization rates must exceed extinction rates for a 
metapopulation to persist (Hanski and Gilpin 1991, pp. 8-9). In recent 
history this balance has not occurred for Peninsular bighorn sheep due 
to fragmentation, disease, predation, and low recruitment (Rubin et al. 
1998, pp. 545-547; Rubin et al. 2002, p. 803-805). In addition to 
fragmentation, remaining subpopulations consist of small, isolated 
groups of bighorn sheep. Small groups are more vulnerable to 
extirpation due to random naturally occurring events, disease, or 
predation because of their small population size. Local extinction of 
small subpopulations can be prevented by occasional immigrants from 
neighboring subpopulations (rescue effect) (Brown and Kodric-Brown 
1977, p. 445).
    Because of the metapopulation structure of the Peninsular bighorn 
sheep population, it is important for genetic exchange and the 
conservation of the subspecies to ensure space for movement and 
connectivity between ewe groups. Furthermore, maintaining connectivity 
within the metapopulation will help safeguard against local extinctions 
of the remaining subpopulations.

Food

    A wide range of forage resources and vegetation associations are 
required by Peninsular bighorn sheep to meet annual and drought-related 
variations in forage quality and availability (Hansen 1980, p. 76). 
Valley floors, rolling hills, and alluvial fans and washes with 
productive soils provide seasonal vegetation and water resources 
important to the Peninsular bighorn sheep. In a mountainous environment 
like the Peninsular Ranges, temperature and soil moisture vary widely 
with slope and elevation. This causes variation in plant growth 
throughout this subspecies' habitat on a seasonal basis. Peninsular 
bighorn sheep need to have access to the seasonal abundance of plant 
life at various elevations to maximize resources and survive in the 
desert environment. Berger (1991, p. 70) found that bighorn sheep 
adjusted their feeding ranges to exploit more nutritive portions of 
their home ranges, such as bajadas, early in the season when high 
protein grasses were emerging. Due to the high energetic costs of 
pregnancy and lactation, ewes are especially dependent on areas with 
nutritious forage to increase success of rearing offspring (Service 
2000, p. 8). Berbach (1987, p. 97) reported that when ewes were 
confined to an enclosure and prevented from using all vegetation 
associations during late gestation and early lactation, they and their 
lambs died of malnutrition. During the reproductive season for 
Peninsular bighorn sheep, ewe foraging is typically concentrated on 
specific sites, such as alluvial fans, bajadas, and washes, where more 
productive, wetter soils support greater herbaceous growth than 
steeper, drier, rockier soils (Service 2000, p. 8). There is a tendency 
for plants that dry out during summer months on the mountain sides to 
remain green longer (and thus more nutritious, higher in protein, and 
more easily digested) because groundwater is generally closer to the 
surface and in greater quantity. Furthermore, the greater soil moisture 
supports a suite of nutritious plants that do not grow on the dry 
mountain sides. Therefore, washes and alluvial fans play an important 
role in allowing desert bighorn sheep to acquire quality forage during 
the heat of summer months and through times of drought.
    In a study of Peninsular bighorn sheep, Scott (1986, p. 21) found 
that

[[Page 57745]]

diets were dominated by shrub species (64 to 76 percent), with grasses 
and forbs species making up a smaller portion of the diet (19 to 30 
percent and 2 to 6 percent, respectively). In the following section, 
plant nomenclature has been updated to conform to treatments in Hickman 
(1993). Common names generally conform with those given in Hickman 
(1993) and/or Abrams et al. (1992-1960). Cited scientific names are 
retained in brackets for ease of reference. Foraging studies by Scott 
(1986, p. 21) and Cunningham (1982, p. 31) noted that Peninsular 
bighorn sheep preferentially feed on different plants seasonally. 
Shrubs such as Ambrosia dumosa (burro bush), Caesalpinia virgata 
[Hoffmannseggia microphylla] (small-leaved Hoffmannseggia), Hyptis 
emoryi (desert lavender), Sphaeralcea spp. (globemallow), and 
Simmondsia chinensis (joboba) are a primary food source year round; 
grasses such as Aristida adscensionis (sixweeks threeawn) and Bromus 
rubens (red brome) along with cacti Opuntia spp. (cholla) are a primary 
food source in the fall; forbs such as Plantago spp. (woolly plantain), 
Plantago ovata [insularis] var. fastigiata (woolly plantain), and 
Ditaxis neomexicana (common ditaxis) are a primary food source in the 
spring. However, Peninsular bighorn sheep are generalist foragers, and 
will browse on a wide variety of plant species depending on seasonal 
availability. Other plants reportedly consumed by Peninsular bighorn 
sheep include Ephedra spp. (Mormon tea), Agave deserti (desert agave), 
Quercus spp. (scrub oak), Phoradendron californicum (desert mistletoe), 
Eriogonum fasciculatum (California buckwheat), Prunus fremontii (desert 
apricot), Acacia greggii (catclaw), Prosopis juliflora (mesquite), 
Krameria grayi (ratany), and Malosma laurina (laurel-leaf sumac) 
(Browning and Monson 1980, p. 88).

Water

    In the Peninsular Ranges, the presence of perennial water is known 
to be a limiting factor only during prolonged droughts or summers 
without significant thunderstorm activity (Service 2000, p. 156). Water 
sources are most valuable to bighorn sheep if they occur in proximity 
to escape terrain with good visibility (Service 2000, p. 9). However, 
bighorn sheep have been observed to travel at least 10 mi (16 km) from 
sources of perennial water. According to Service biologists familiar 
with the subspecies, bighorn sheep usually visit a water source every 2 
to 3 days, but it is not unusual for them to drink more often. During 
the hot summer months, desert bighorn sheep typically stay close to 
reliable sources of water and drink large quantities of water at a 
time. It has been hypothesized that desert bighorn sheep can survive 
without a permanent water source, although this view is not widely 
accepted (Turner and Weaver 1980, p. 104). In desert ranges like the 
Peninsular Ranges, rainwater can collect in natural collection tanks 
and potholes in the rock and provide seasonal or perennial water 
sources. Natural springs also provide a reliable source of water for 
Peninsular bighorn sheep. Desert sheep also rely on consuming 
vegetation, including cacti, to meet water requirements when standing 
water sources are scarce (Turner and Weaver 1980, p. 102). Water is 
especially important to lactating ewes, as they need sufficient water 
to produce milk. Water sources contribute greatly to the Peninsular 
bighorn sheep's ability to survive the hot and dry summer months.

Primary Constituent Elements for the Peninsular Bighorn Sheep

    Within the geographical area occupied by the Peninsular bighorn 
sheep at the time of listing, we must identify the PCEs that may 
require special management considerations or protection.
    Based on the above needs and our current knowledge of the life 
history, biology, and ecology of the subspecies, we have determined 
that the Peninsular bighorn sheep's PCEs are:
    (1) Moderate to steep, open slopes (20 to 60 percent) and canyons, 
with canopy cover of 30 percent or less (below 4,600 feet (1,402 
meters) elevation in the Peninsular Ranges) that provide space for 
sheltering, predator detection, rearing of young, foraging and 
watering, mating, and movement within and between ewe groups.
    (2) Presence of a variety of forage plants, indicated by the 
presence of shrubs (e.g., Ambrosia spp., Caesalpinia spp., Hyptis spp., 
Sphaeralcea spp., Simmondsia spp.), that provide a primary food source 
year round, grasses (e.g., Aristida spp., Bromus spp.) and cacti (e.g., 
Opuntia spp.) that provide a source of forage in the fall, and forbs 
(e.g., Plantago spp., Ditaxis spp.) that provide a source of forage in 
the spring.
    (3) Steep, rugged, slopes (60 percent slope or greater) (below 
4,600 feet (1,402 meters) elevation in the Peninsular Ranges) that 
provide secluded space for lambing as well as terrain for predator 
evasion.
    (4) Alluvial fans, washes, and valley bottoms that provide 
important foraging areas where nutritious and digestible plants can be 
more readily found during times of drought and lactation and that 
provide and maintain habitat connectivity by serving as travel routes 
between and within ewe groups, adjacent mountain ranges, and important 
resources areas, such as foraging areas and escape terrain.
    (5) Intermittent and permanent water sources that are available 
during extended dry periods and that provide relatively nutritious 
plants and drinking water.
    This proposed revision to currently designated critical habitat for 
the Peninsular bighorn sheep is designed for the conservation of PCEs 
necessary to support the life history functions that are the basis for 
our proposal and the areas containing those PCEs.
    We propose units for designation based on sufficient PCEs being 
present to support at least one of the subspecies' life history 
functions. For this subspecies, all of the units proposed contain all 
of the PCEs and support the multiple essential life history functions 
identified above.

Special Management Considerations or Protection

    When designating critical habitat, we assess whether the occupied 
areas contain the features that are essential to the conservation of 
the subspecies and that may require special management considerations 
or protection. We have also considered how revising the current 
critical habitat designation for the Peninsular bighorn sheep 
highlights habitat that needs special management considerations or 
protection.
    Peninsular bighorn sheep habitat and the PCEs upon which the sheep 
depends are threatened by the direct and indirect effects of: 
Development and expansion of urban areas; human disturbance related to 
recreation; construction of roadways and power lines; and mineral 
extraction and mining operations.
    The development and expansion of urban and associated industrial 
areas threaten Peninsular bighorn sheep and their habitat through 
direct and indirect effects. Habitat loss (especially in canyon 
bottoms), degradation, and fragmentation associated with the 
proliferation of residential and commercial development, roads and 
highways, water projects, and vehicular and pedestrian recreational 
uses threaten the Peninsular bighorn sheep throughout its range (63 FR 
13134; March 18, 1998). The cities that occur along the eastern 
boundary of proposed revised critical habitat, from the base of the San 
Jacinto and Santa Rosa Mountains to the Salton Sea area (Units

[[Page 57746]]

1 and 2A), continue to grow. Development adjacent to and within 
Peninsular bighorn sheep habitat affects the quality and quantity of 
lower elevation habitat and associated vegetation, alluvial fans, and 
water sources (PCEs 1, 2, 4, and 5). By 2000, at least 18,500 ac (7,490 
ha) of suitable Peninsular bighorn sheep habitat had been lost to 
urbanization and agriculture along the urban interface between the 
cities of Palm Springs and La Quinta (Service 2000, p. 38). Much of the 
lost habitat consisted of low elevation alluvial fans and washes that 
provided important sources of nutrients to ewes when they are rearing 
their lambs (PCE 2 and 4) (66 FR 8650; February 1, 2001). Moreover, in 
the northern Santa Rosa Mountains, from 1991 to 1996, 34 percent of 
adult mortalities appear to have been directly caused by urbanization 
(66 FR 8650; February 1, 2001). Five Peninsular bighorn sheep were 
killed by cars; five died from feeding on toxic, nonnative ornamental 
plants; and one was strangled in a wire fence (DeForge and Ostermann 
1997, p. 1).
    Continued urban and commercial development within the range of 
Peninsular bighorn sheep could fragment the Peninsular bighorn sheep 
metapopulation into isolated groups too small to maintain long-term 
viability. Maintenance of genetic diversity allows small ewe groups 
like those in the Peninsular Ranges to persist. The inability of rams 
and occasional ewes to move between groups erodes the genetic fitness 
of isolated groups (PCE 1 and 4) (63 FR 13134; March 18, 1998). Special 
management considerations or protection may be needed to alleviate the 
effects of development on Peninsular bighorn sheep habitat, especially 
lower elevation habitat, alluvial fans, and areas of possible ewe group 
connectivity near urban areas. This protection could be accomplished by 
controlling the expansion of urban, industrial, and agricultural 
development into these areas.
    In the Peninsular Ranges (Units 1, 2 and 3), increased activity and 
disturbance adjacent to, and within Peninsular bighorn sheep habitat 
are adversely affecting bighorn sheep by altering their normal 
behavior. This altered behavior can lead to abandonment of habitat and 
prevent use of preferred habitat, including lambing areas, water 
sources, and foraging areas, and cause negative physiological effects 
(PCE 1, 2, 3, 4, and 5) (66 FR 8650; 63 FR 13134). A variety of human 
activities, such as hiking, mountain biking, horseback riding, camping, 
hunting, livestock grazing, and use of aircraft and off-road vehicles, 
have the potential to disrupt normal bighorn sheep social behaviors. 
Special management considerations or protection may be needed to 
alleviate the effects of human activity and disturbance to Peninsular 
bighorn sheep. Restricting human use of trail systems and natural areas 
during lambing season and exclusionary fencing around urban areas may 
reduce human effects on Peninsular bighorn sheep behavior.
    Roadways and power line structures occur in, and are proposed for 
construction within, Peninsular bighorn sheep habitat. Two major 
highways run through the Peninsular Ranges and fragment bighorn sheep 
habitat. In the northern portion of the Peninsular Ranges, State Route 
74 runs through the Santa Rosa Mountains (Unit 2A). Further south, 
State Route 78 cuts through habitat between the San Ysidro Mountains 
and Pinyon Mountains (Unit 2B). These roadways have degraded habitat 
and have generally impeded the movement of Peninsular bighorn sheep 
(especially ewes) between ewe groups in the surrounding areas (PCE 1, 
2, 3, 4, and 5) (Rubin et al. 1998, p. 547), which can erode the 
genetic fitness of isolated groups (63 FR 13134; March 18, 1998). 
However, some movement has been documented across State Route 74 
(Service 2004, pp. 1-2). Epps et al. (2005, p. 1035) showed that 
nuclear genetic diversity of desert bighorn sheep populations was 
negatively correlated with the presence of human-made barriers 
(highways), which essentially eliminated dispersal. Furthermore, in 
some portions of their range, collisions with automobiles can be a 
significant cause of Peninsular bighorn sheep mortality (DeForge and 
Ostermann 1997, p. 1). The construction of power lines and associated 
structures may also degrade and fragment bighorn sheep habitat. 
Currently, a large power line (Sunrise Powerlink) is proposed for 
construction through Unit 2B along Highway 78. Special management 
considerations or protection may be needed to alleviate the effects of 
roadway and power line structures on Peninsular bighorn sheep and their 
habitat. Future construction of roadways and power lines should be 
avoided, and if unavoidable, should be constructed in a way that 
minimizes effects to habitat and allows for continued connectivity 
among ewe groups.
    Mining operations occur within southern portions of the habitat 
used by Peninsular bighorn sheep. Mining activities and associated 
facilities threaten Peninsular bighorn sheep by causing the loss of 
vegetation structure required for foraging activities and destroying 
habitats used for escape, bedding, lambing, or connectivity between 
ranges (PCE 1, 2, 3, 4, and 5). Disturbance could modify the sheep's 
behavior or cause bighorn sheep to flee an area. Mining occurs within 
the habitat of Peninsular bighorn sheep in Units 2B and 3. Special 
management considerations or protection may be needed to alleviate the 
effects of mining operations on Peninsular bighorn sheep habitat. 
Further mining operations should avoid to the maximum extent possible, 
areas considered essential to Peninsular bighorn sheep conservation.

Criteria Used To Identify Critical Habitat

    All proposed revised critical habitat units are within areas that 
we have determined were occupied at the time of listing, and that 
contain sufficient PCEs to support the life history functions essential 
for the conservation of the subspecies. Lands were proposed for 
designation based on sufficient PCEs being present to support the life 
processes.
    We used the following data to delineate proposed revised critical 
habitat: (1) Areas known to be occupied at the time of listing (1998) 
and currently occupied; (2) areas within the ewe group distribution 
(subpopulations) boundaries identified by Rubin et al. (1998); (3) 
areas where occupancy data points indicate repeated Peninsular bighorn 
sheep use, but which were not captured within the ewe groups 
distribution boundaries identified by Rubin et al. (1998); and (4) 
areas that contain the PCEs required by the subspecies as determined 
from aerial imagery and GIS data on vegetation, elevation, and slope.
    We also gathered information from our files, staff biologists, the 
California Department of Fish and Game, the Bighorn Institute, and Dr. 
Ester Rubin. Our proposed revision to critical habitat is designed to 
capture ewe groups; lambing areas; foraging areas, including alluvial 
fans; water sources; ram groups; and areas used for associated herd 
(male, female, and young) movements and migrations.
    We delineated the proposed revised critical habitat boundaries 
using the following steps:
    (1) As a first step in the delineation process, we mapped ewe group 
areas from Rubin et al. (1998) over GIS imagery of the Peninsular 
Ranges to delineate the distribution of ewe groups in the proposed 
revised critical habitat. We consider Rubin et al. (1998) to be the 
best available data on Peninsular bighorn sheep ewe group distribution.

[[Page 57747]]

Rubin et al. (1998) examined the population structure, distribution, 
and abundance of Peninsular bighorn sheep in California using 
observational data from radio-collared and uncollared male (ram) and 
female (ewe) sheep between 1971 and 1996. This is the only data we are 
aware of that identifies the distribution of ewe groups and subgroups 
within the Peninsular Ranges.
    (2) To ensure that Rubin et al. (1998, pp. 539-561) still 
accurately represents the boundaries of the ewe groups and to capture 
possible ram movement, we compared the ewe group delineation from Rubin 
et al. (1998, pp. 539-561) with all occupancy data collected since the 
time of listing on GIS imagery maps. We then expanded the ewe group 
delineation to include areas where occupancy data points indicate 
repeated Peninsular bighorn sheep use and recent sheep movements (post 
Rubin et al. 1998, pp. 539-561), and areas that contain the PCEs for 
Peninsular bighorn sheep. In particular, we expanded the northernmost 
ewe group delineation (San Jacinto Mountains) to include the area north 
of Chino Canyon where (1) we have evidence of recent ewe and ram 
movements and (2) the Bighorn Institute has released, and continues to 
release, captive-born sheep to help recover this subspecies. We also 
expanded the southernmost ewe group delineation (Carizzo Canyon area) 
to the south to capture water sources (PCE 5), including habitat near 
the Interstate 8-State Route 98 split, where there are consistent, 
recent sightings of uncollared Peninsular bighorn sheep.
    (3) We then examined all pre-listing occurrence data in our files 
to determine if our revised critical habitat missed any areas of 
historical repeated Peninsular bighorn sheep use. We identified an area 
of historical repeated use that was occupied at the time of listing 
between two ewe subgroups documented in Rubin et al. (1998, pp. 539-
561) as (1) Santa Rosa Mountains east of State Route 74 (Martinez 
Canyon) and (2) Santa Rosa Mountains east of State Route 74 (south)). 
Use of this area is consistent with the Rubin et al. (1998, pp. 539-
561) demographic study, which indicated possible connectivity between 
these subgroups through this area. This area is important in light of 
genetic findings by Boyce et al. (1999, pp. 99-106) that indicate ewe 
groups within these ranges maintain genetic connectivity, probably 
through male-mediated nuclear gene flow. Based on the importance of 
this area for connectivity between subgroups, we expanded the proposed 
revised critical habitat boundaries to include areas where occupancy 
data points indicate historically occupied habitat. Since the number of 
occurrence data points in historically occupied areas is relatively 
small, we delineated the unit boundaries in these areas to follow the 
boundaries of the PCEs, such as elevations below 4,600 ft (1,400 m), 
areas with 30 percent canopy cover or less, escape terrain, alluvial 
fans, washes, and water sources immediately adjacent to the identified 
ewe groups.
    (4) As a final step in refining our delineation, we closely 
examined our revised units to ensure they capture all of the PCEs to 
support life history functions essential for the conservation of the 
subspecies. Where appropriate, we expanded the boundaries to capture 
the extent of an alluvial fan or water source (PCE 4 or 5, 
respectively). We also removed areas that we determined do not contain 
the PCEs or otherwise do not contain suitable Peninsular bighorn sheep 
habitat, such as areas above 4,600 ft (1,400 m) elevation (PCE 1), 
areas containing conifer woodland with canopy cover greater than 30 
percent (PCE 1), and slopes less than 20 percent (PCE 1), unless those 
areas overlapped specifically with Rubin et al.'s (1998, pp. 539-561) 
ewe group distributions and had documented use by Peninsular bighorn 
sheep.
    On May 22, 2007, Drs. Esther Rubin and Walter Boyce, in cooperation 
with Steve Torres and Chris Stermer of the California Department of 
Fish and Game, submitted a draft predictive habitat model for bighorn 
sheep in the Peninsular Ranges. We did not adopt this predictive 
habitat model to delineate critical habitat because the model was 
submitted in draft form, prior to final steps of model validation and 
peer review, and model development was based on just two years of 
Global Positioning System (GPS) data (Rubin 2007, p. 2); nevertheless, 
the model supports our proposed delineation. Areas we are designating 
roughly fall within the upper level habitat suitability classes derived 
from the preliminary model.
    When determining the proposed revisions to critical habitat 
boundaries within this proposed rule, we made every effort to avoid 
including developed areas such as buildings, paved areas, and other 
structures that lack PCEs for the Peninsular bighorn sheep. 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 areas. Any such structures and the land under them 
inadvertently left inside critical habitat boundaries shown on the maps 
of this proposed revision to critical habitat have been excluded by 
text in the proposed rule and are not proposed for designation as 
revised critical habitat. Therefore, Federal actions limited to these 
areas would not trigger section 7 consultation, unless they may affect 
the subspecies or primary constituent elements in adjacent critical 
habitat.

Summary of Proposed Changes From Previously Designated Critical Habitat

    The areas identified in this proposed rule constitute a proposed 
revision to the areas we designated as critical habitat for the 
Peninsular bighorn sheep on February 1, 2001 (66 FR 8650). The main 
differences include the following:
    (1) The 2001 final rule used a generalized methodology for 
delineating critical habitat that resulted in the designation of one 
critical habitat unit for Peninsular bighorn sheep totaling 844,897 ac 
(341,919 ha) (66 FR 8650; February 1, 2001). This proposed revision is 
based on a more specific methodology that resulted in three critical 
habitat units including approximately 384,410 ac (155,564 ha) of land 
in Riverside, San Diego, and Imperial counties, California, a reduction 
of 460,487 ac (186,355 ha) from the 2001 final rule (66 FR 8650). The 
areas included in this proposed revised critical habitat are almost 
entirely within the boundaries of the existing (2001) critical habitat. 
There are approximately 72 ac (29 ha) of BLM land in Unit 3 that are 
outside the boundary of the 2001 critical habitat.
    The reduction in total area from the 2001 final critical habitat 
designation is primarily the result of using a revised methodology to 
delineate critical habitat in this proposed revision. In our 2001 final 
critical habitat designation, we delineated critical habitat based on 
the methodology used in the Recovery Plan for Bighorn Sheep in the 
Peninsular Ranges, California (Service 2000).
    In developing this proposed revision, we reexamined the methodology 
outlined in the 2000 recovery plan and the 2001 critical habitat 
designation, and updated that methodology based on the best available 
information to identify areas essential for the conservation of the 
subspecies (see ``Criteria Used To Identify Critical Habitat'' 
section). Since publication of the 2000 recovery plan and the 2001 
critical habitat designation, more specific and up-to-date information 
has become available regarding habitat use by Peninsular bighorn sheep 
and areas containing the features essential to the conservation of this 
subspecies. New information indicates that many areas included in the 
2001 critical habitat

[[Page 57748]]

designation do not support the features essential for the conservation 
of the Peninsular bighorn sheep and/or otherwise contain unsuitable 
habitat for the subspecies. For example, the 2001 final rule included 
high elevation (above 4,600 ft (1,402 m)), densely vegetated, and 
forested habitat that is inappropriate for sheep use in the San 
Jacinto, Santa Rosa, and Vallecito Mountains. The differences between 
the generalized methodology applied in the 2001 critical habitat 
designation and the methodology used in this proposed rule, including 
our reasons for revising the approach, are outlined below.
    The recovery plan generally used two criteria, the presence of 
escape terrain and unobstructed view, as key habitat requirements when 
delineating the areas essential to Peninsular bighorn sheep with little 
consideration of the presence of the PCEs required by this subspecies. 
In this proposed revision, we have considered all five of the revised 
PCEs in delineating proposed revised critical habitat which results in 
a more precise determination of essential habitat (see ``Primary 
Constituent Elements for the Peninsular Bighorn Sheep'' and ``Criteria 
Used to Identify Critical Habitat'' sections).
    Additionally, little consideration was given to occurrence data in 
the recovery plan methodology and specific ewe group distributions, 
resulting in expanses of critical habitat in the 2001 designation in 
which we have little to no occurrence records that would indicate sheep 
use those areas. For example, we have occupancy data dating back to 
1940, yet extensive areas along the western and southern boundary of 
the 2001 designation contain little to no documented sheep use. In 
light of all the recent research efforts and occupancy data, we are not 
including those lands in this proposed revision as we have determined 
that those lands are not essential to the conservation of Peninsular 
bighorn sheep. Because a detailed vegetation map was not available at 
the time of the recovery plan, a team of biologists flew the entire 
western boundary in a helicopter and visually assessed vegetation 
associations (Service 2000, p. 159). The western boundary was 
determined by consensus and recorded by GPS from the helicopter 
position every ten seconds (Service 2000, p. 159). A 0.5 mi (0.8 km) 
buffer was added to this line to account for the advent of fire 
suppression (Service 2000, p. 160). In determining the western boundary 
of essential habitat in this proposed revision, we used vegetation maps 
that cover the entire range of the Peninsular bighorn sheep, along with 
detailed aerial photography, expert opinion, and sheep use data to 
delineate boundaries, which we have determined more precisely captures 
the areas essential to the subspecies.
    Like our methodology for this proposed revision, the 2001 
methodology used a minimum slope criterion of 20 percent to delineate 
essential habitat; however, a 0.5 mi (0.8 km) buffer was included 
around slopes of greater than or equal to 20 percent (Service 2000, p. 
158). This proposed rule does not include a buffer zone area around 
habitat determined to be essential to the subspecies.
    In summary, we consider the recent data and methodology used in 
this proposed revision to more accurately and specifically delineate 
the areas essential to the Peninsular bighorn sheep. The methods used 
in the 2000 recovery plan and the 2001 critical habitat designation 
resulted in a more inclusive delineation of essential habitat due to 
limited data. Application of the revised methodology, based on the best 
available information, identified 460,487 ac (186,355 ha) of previously 
designated critical habitat that is not essential to the subspecies, 
and therefore we are not including these areas in this proposed 
revision to the critical habitat designation.
    (2) We re-evaluated and revised the PCEs in li