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CFR Citation: 50 CFR Part 17

RIN ID: RIN 1018-AV09

NOTICE: Part III

DOCUMENT ACTION: Proposed rule.

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

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.

DOCUMENT 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.

SUMMARY: Interior Department, Fish and Wildlife Service,

SUPPLEMENTAL INFORMATION

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, ``GovernmenttoGovernment 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 email to submit your comments, please include ``Attn: Peninsular bighorn sheep'' in your email 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 email, contact us directly by calling our Carlsbad Fish and Wildlife Office at 760 4319440. 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, email address, or other personal identifying information in your comment, you should be aware that your entire commentincluding your personal identifying informationmay 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 7604319440).

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 droughtrelated 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 rangewide 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 [[Page 57742]]
augmenting and reestablishing wild populations (Ostermann et al. 2001, p. 751). Captivebred 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 6month 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, courtapproved 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. 106554; 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 peerreviewed 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 peerreviewed 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 northfacing 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
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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 6month 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. 182183; Bleich et al. 1990, p. 386). This approach considers longterm 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 humanconstructed 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 aerialtelemetry locations and genetic analysis revealed ram movement between up to three ewe groups (Boyce et al. 1999, p. 99; Rubin et al. 1998, pp. 543544). Substructuring also can occur within single herds (ewe groups) of bighorn sheep (FestaBianchet 1986, pp. 327330; Andrew et al. 1997, pp. 7475; Rubin et al. 1998, pp. 543548). Such substructuring is defined by separate home range patterns. Although demonstrated more with females, it can occur in both sexes.

Another important longterm 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. 89). 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. 545547; Rubin et al. 2002, p. 803805). 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 KodricBrown 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 droughtrelated 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
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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. (19921960). 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] (smallleaved 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 (laurelleaf 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 longterm 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 offroad 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. 12). Epps et al. (2005, p. 1035) showed that nuclear genetic diversity of desert bighorn sheep populations was negatively correlated with the presence of humanmade 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 radiocollared 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. 539561) 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. 539561) 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. 539561), 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, captiveborn 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 8State Route 98 split, where there are consistent, recent sightings of uncollared Peninsular bighorn sheep.
(3) We then examined all prelisting 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. 99106) that indicate ewe groups within these ranges maintain genetic connectivity, probably through malemediated 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. 539561) 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 uptodate 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
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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 reevaluated and revised the PCEs in light of the Alameda whipsnake court case (Homebuilder's Ass'n of Northern Cal. v. U.S. Fish and Wildlife Service, 268 F. Supp.2d 1197 (E.D. Cal. 2003)) and other relevant case law, and followed current Service guidelines and policies. The PCEs differ from those in the existing critical habitat rule in that they are reorganized into five separate PCEs for clarity. Furthermore, we have added specific information on elevational range, plant species used for foraging, and range of slopes required by the subspecies. This additional specificity was gained by evaluating the recovery plan and examining all recent sheep data, including data from radio collars and GPS collars providing precision to the identification of habitats used and preferred by Peninsular bighorn sheep. Applying the more precise PCEs to the mountain ranges inhabited by Peninsular bighorn sheep allowed us to fine tune the proposed revision to those areas containing preferred habitat for sheep use, and removing those areas unlikely to be used by Peninsular bighorn sheep.
(3) Approximately 29,924 ac (12,110 ha) of designated critical habitat were vacated in the July 31, 2006, consent decree. A portion of those acres are now within proposed revised critical habitat. Of the 13,213 ac (5,347 ha) of vacated Agua Caliente Band of Cahuilla Indians Tribal lands, approximately 4,512 ac (1,826 ha) are now included in this proposal. However, we are proposing to exclude all Tribal lands from the final designation. Approximately 16,691 ac (6,756 ha) of mining lands at Ocotillo Mineral Material Sites and Fish Canyon Quarry property were vacated. In this proposed revision to critical habitat we are including roughly 50 percent of those vacated lands; specifically, we are including lands along the northernmost portion of the Ocotillo Mineral Material Sites property and the middle to southern portion of the Fish Canyon Quarry property. Both of these mining properties contain actively mined lands, but also contain areas in which we have recent documented use by Peninsular bighorn sheep and areas that meet the criteria used to identify critical habitat as described above. The Desert Riders lands vacated in the consent decree (approximately 20 ac (8 ha)) are not included in this proposed revision.

Our 2001 final critical habitat rule included the statement that ``* * *; we are not aware of any information suggesting that particular areas within designated critical habitat are currently unsuitable or unused over the generational timeframe needed for the longterm conservation of bighorn sheep in the Peninsular Ranges'' (66 FR 8655). However, we have reconsidered the information that was available to us at the time of the 2001 designation in light of all the information currently available to us, and we have determined that the methodology used in this proposed revision, which utilized the best available information, provides a more accurate and specific delineation of the areas essential to the Peninsular bighorn sheep, than that relied upon in the 2001 critical habitat designation.

Proposed Revisions to the Critical Habitat Designation

We are proposing four units as critical habitat for the Peninsular bighorn sheep. These units, which are almost entirely within the area included in the 2001 designation, if finalized, would replace the current critical habitat designation for the Peninsular bighorn sheep at 50 CFR 17.95(a). The critical habitat areas we describe below constitute our current best assessment of areas that meet the definition of critical habitat for the Peninsular bighorn sheep. Table 1 shows the occupancy status of each unit being proposed as revised critical habitat.
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Table 1.Occupancy Status of Critical Habitat Units Proposed for the Peninsular Bighorn Sheep Occupied at time of Size of proposed revised critical Unit listing? Currently occupied? habitat unit in acres (Hectares) 1. San Jacinto Mts.............. Yes................ Yes................ 15,273 (6,180 ha). 2A. N. Santa Rosa Mts........... Yes...

FOR FURTHER INFORMATION CONTACT Jim Bartel, Field Supervisor, Carlsbad Fish and Wildlife Office, 6010 Hidden Valley Road, Carlsbad, CA 92011; telephone 7604319440 ; facsimile 7604315901. If you use a
telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 8008778339.