Endangered and Threatened Wildlife and Plants; Designation of Critical Habitat for the Southern California Distinct Population Segment of the Mountain Yellow-Legged Frog (Rana muscosa, 54344-54386 [06-7578]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 71, Number 178 (Thursday, September 14, 2006)]
[Rules and Regulations]
[Pages 54344-54386]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 06-7578]



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Part II





 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 Southern California Distinct Population Segment of the 
Mountain Yellow-Legged Frog (Rana muscosa); Final Rule

Federal Register / Vol. 71, No. 178 / Thursday, September 14, 2006 / 
Rules and Regulations

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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

RIN 1018-AU30


Endangered and Threatened Wildlife and Plants; Designation of 
Critical Habitat for the Southern California Distinct Population 
Segment of the Mountain Yellow-Legged Frog (Rana muscosa)

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Final rule.

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SUMMARY: We, the U.S. Fish and Wildlife Service (Service), are 
designating critical habitat for the southern California distinct 
population segment of the mountain yellow-legged frog (Rana muscosa) 
pursuant to the Endangered Species Act of 1973, as amended (Act). In 
total, approximately 8,283 acres (ac) (3,352 hectares (ha)) fall within 
the boundaries of the critical habitat designation. The critical 
habitat is located in Los Angeles, San Bernardino, and Riverside 
Counties, California.

DATES: This rule becomes effective on October 16, 2006.

ADDRESSES: Comments and materials received, as well as supporting 
documentation used in the preparation of this final 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, California 92011 (telephone 760/431-9440). The final 
rule, economic analysis, and maps are available via the Internet at 
https://www.fws.gov/carlsbad/.

FOR FURTHER INFORMATION CONTACT: Jim Bartel, Field Supervisor, Carlsbad 
Fish and Wildlife Office, 6010 Hidden Valley Road, Carlsbad, California 
92011, (telephone 760/431-9440; facsimile 760/431-9624).

SUPPLEMENTARY INFORMATION:

Role of Critical Habitat in Actual Practice of Administering and 
Implementing the Act

    Attention to and protection of habitat is paramount to successful 
conservation actions. The role that designation of critical habitat 
plays in protecting habitat of listed species, however, is often 
misunderstood. As discussed in more detail below in the discussion of 
exclusions under section 4(b)(2) of the Act (16 U.S.C. 1513 et seq.), 
there are significant limitations on the regulatory effect of 
designation under ESA section 7(a)(2) of the Act. In brief, (1) 
Designation provides additional protection to habitat only where there 
is a federal nexus; (2) the protection is relevant only when, in the 
absence of designation, destruction or adverse modification of the 
critical habitat would in fact take place (in other words, other 
statutory or regulatory protections, policies, or other factors 
relevant to agency decision-making would not prevent the destruction or 
adverse modification); and (3) designation of critical habitat triggers 
the prohibition of destruction or adverse modification of that habitat, 
but it does not require specific actions to restore or improve habitat.
    Currently, 475 species, or 36 percent of the 1,310 listed species 
in the U.S. under the jurisdiction of the Service, have designated 
critical habitat. We address the habitat needs of all 1,310 listed 
species through conservation mechanisms such as listing, section 7 
consultations, the section 4 recovery planning process, the section 9 
protective prohibitions of unauthorized take, section 6 funding to the 
States, the section 10 incidental take permit process, and cooperative, 
nonregulatory efforts with private landowners. We believe that it is 
these measures that may make the difference between extinction and 
survival for many species.
    In considering exclusions of areas originally proposed for 
designation, we evaluated the benefits of designation in light of 
Gifford Pinchot Task Force v. United States Fish and Wildlife Service. 
In that case, the Ninth Circuit invalidated the Service's regulation 
defining ``destruction or adverse modification of critical habitat.'' 
In response, on December 9, 2004, the Director issued guidance to be 
considered in making section 7 adverse modification determinations. 
This critical habitat designation does not use the invalidated 
regulation in our consideration of the benefits of including areas in 
this final designation. The Service will carefully manage future 
consultations that analyze impacts to designated critical habitat, 
particularly those that appear to be resulting in an adverse 
modification determination. Such consultations will be reviewed by the 
Regional Office prior to finalizing to ensure that an adequate analysis 
has been conducted that is informed by the Director's guidance.
    On the other hand, to the extent that designation of critical 
habitat provides protection, that protection can come at significant 
social and economic cost. In addition, the mere administrative process 
of designation of critical habitat is expensive, time-consuming, and 
controversial. The current statutory framework of critical habitat, 
combined with past judicial interpretations of the statute, make 
critical habitat the subject of excessive litigation. As a result, 
critical habitat designations are driven by litigation and courts 
rather than biology, and made at a time and under a time frame that 
limits our ability to obtain and evaluate the scientific and other 
information required to make the designation most meaningful.
    In light of these circumstances, the Service believes that 
additional agency discretion would allow our focus to return to those 
actions that provide the greatest benefit to the species most in need 
of protection.

Procedural and Resource Difficulties in Designating Critical Habitat

    We have been inundated with lawsuits for our failure to designate 
critical habitat, and we face a growing number of lawsuits challenging 
critical habitat determinations once they are made. These lawsuits have 
subjected the Service to an ever-increasing series of court orders and 
court-approved settlement agreements, compliance with which now 
consumes nearly the entire listing program budget. This leaves the 
Service with little ability to prioritize its activities to direct 
scarce listing resources to the listing program actions with the most 
biologically urgent species conservation needs.
    The consequence of the critical habitat litigation activity is that 
limited listing funds are used to defend active lawsuits, to respond to 
Notices of Intent (NOIs) to sue relative to critical habitat, and to 
comply with the growing number of adverse court orders. As a result, 
listing petition responses, the Service's own proposals to list 
critically imperiled species, and final listing determinations on 
existing proposals are all significantly delayed.
    The accelerated schedules of court-ordered designations have left 
the Service with limited ability to provide for public participation or 
to ensure a defect-free rulemaking process before making decisions on 
listing and critical habitat proposals, due to the risks associated 
with noncompliance with judicially imposed deadlines. This in turn 
fosters a second round of litigation in which those who fear adverse 
impacts from critical habitat designations challenge those 
designations. The cycle of litigation appears endless, and is very 
expensive, thus diverting resources from conservation actions that may 
provide relatively more benefit to imperiled species.

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    The costs resulting from the designation include legal costs, the 
cost of preparation and publication of the designation, the analysis of 
the economic effects and the cost of requesting and responding to 
public comment, and in some cases the costs of compliance with the 
National Environmental Policy Act (NEPA) (42 U.S.C. 4321 et seq.). 
These costs, which are not required for many other conservation 
actions, directly reduce the funds available for direct and tangible 
conservation actions.

Background

    It is our intent to discuss only those topics directly relevant to 
the designation of critical habitat in this rule. For more information 
on the southern California distinct population segment (DPS) of the 
mountain yellow-legged frog, hereafter referred to as the mountain 
yellow-legged frog, refer to the final listing rule published in the 
Federal Register on July 2, 2002 (67 FR 44382) and the proposed 
critical habitat designation published in the Federal Register on 
September 13, 2005 (70 FR 54106).

Previous Federal Actions

    Previous Federal actions for the mountain yellow-legged frog can be 
found in our proposal to designate critical habitat for the mountain 
yellow-legged frog published in the Federal Register on September 13, 
2005 (70 FR 54106). That information is incorporated by reference into 
this final rule.

Summary of Comments and Recommendations

    We requested written comments from the public on the proposed 
designation of critical habitat for the mountain yellow-legged frog in 
the proposed rule published on September 13, 2005 (70 FR 54106). We 
also requested written comments from the public on the draft economic 
analysis (DEA) of the proposed designation in a notice of availability 
published on July 3, 2006 (71 FR 37881). We contacted appropriate 
Federal, State, and local agencies; scientific organizations; and other 
interested parties and invited them to comment on the proposed rule and 
the DEA.
    During the comment period that opened on September 13, 2005, and 
closed on November 14, 2005, we received 11 comments directly 
addressing the proposed critical habitat designation. Of these 
comments, five were from peer reviewers, two from Federal agencies, and 
four from organizations or individuals. During the comment period that 
opened on July 3, 2006, and closed on July 24, 2006, we received no 
comments directly addressing the proposed critical habitat designation 
and one comment directly addressing the DEA. Of all comments received 
during both comment periods, five commenters supported the designation 
of critical habitat for the mountain yellow-legged frog and two opposed 
the designation. Five letters included comments or information, but did 
not express support or opposition to the proposed critical habitat 
designation. Comments received were grouped into two general issues 
specifically relating to the proposed critical habitat designation for 
the mountain yellow-legged frog and are addressed in the following 
summary and/or incorporated into the final rule as appropriate. We did 
not receive any requests for a public hearing.
    We reviewed all comments received from the peer reviewers and the 
public for substantive issues and new information regarding critical 
habitat for the mountain yellow-legged frog, and we address them in the 
following summary.

Peer Review

    In accordance with our policy published on July 1, 1994 (59 FR 
34270), we solicited expert opinions from five knowledgeable 
individuals with scientific expertise that included familiarity with 
the species, the geographic region in which the species occurs, and 
conservation biology principles. We received responses from all five 
peer reviewers. The peer reviewers generally agreed with our methods 
and conclusions and provided additional information, clarifications, 
and suggestions to improve the final critical habitat rule. Four of the 
five reviewers supported the designation and emphasized the importance 
of including unoccupied areas. Peer reviewer comments are addressed in 
the following summary and incorporated into the final rule as 
appropriate.

Peer Reviewer Comments

    (1) Comment: Several peer reviewers supported our proposed 
designation. In addition, several of the peer reviewers strongly 
supported our inclusion of unoccupied areas and encouraged inclusion of 
additional unoccupied areas due to the small number of sites that 
support known populations, the presence of suitable habitat in 
unoccupied sites with historical occurrence records, and the 
uncertainty in determining streams as unoccupied because of the 
difficulty in detecting this cryptic species.
    Our Response: We appreciate the peer reviewers' comments and 
concerns for including unoccupied areas. We believe that designating 
critical habitat in streams not known to be currently occupied, but 
historically occupied, will assist in the conservation of the mountain 
yellow-legged frog by identifying possible reintroduction sites or 
facilitating natural recovery by expansion of very small populations. 
The peer reviewers did not provide us with site-specific information on 
other areas that should also be included in the critical habitat 
designation, and we did not include additional unoccupied habitat in 
the final designation.
    (2) Comment: One peer reviewer cited new information from the 2005 
mountain yellow-legged frog survey efforts conducted by the United 
States Geological Survey (USGS). The peer reviewer reported the 
rediscovery of mountain yellow-legged frog metamorphs in East Fork of 
City Creek in the San Bernardino Mountains in September of 2005. This 
rediscovery was surprising since all of the surviving frogs were 
thought to have been collected and moved to a captive-rearing facility 
after the 2003 fire and flood events. The peer reviewer also reported 
the rediscovery of young tadpoles in Dark Canyon in the San Jacinto 
Mountains in August of 2005 after more than five years of survey 
efforts that did not detect this species. The peer reviewer also stated 
that no mountain yellow-legged frogs were detected in Bear Gulch in the 
San Gabriel Mountains during three survey efforts in 2005, despite this 
population being one of the two largest remaining populations in 
southern California as of 2003.
    Our Response: The recent rediscovery of mountain yellow-legged 
frogs in City Creek and in Dark Canyon highlights the difficulty in 
detecting this species and highlights the uncertainty in determining 
whether a stream is truly unoccupied by mountain yellow-legged frogs 
after negative survey efforts, especially when these streams were 
recently known to be occupied. For this reason, we are still 
considering Bear Gulch as occupied for this final designation. City 
Creek and Dark Canyon were already considered occupied in the proposed 
rule, and therefore there is no change in their occupancy status for 
the final rule.
    (3) Comment: One peer reviewer reported that chytrid fungal disease 
was discovered in wild frogs that were recently rediscovered in the 
East Fork of City Creek in September 2005 and in the captive frogs 
taken from the same creek in 2004, thus changing our perception of the 
areas that are known to contain this

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disease. The peer reviewer stated that it was unusual to find living 
frogs infected with chytrid because it generally kills infected frogs. 
The peer reviewer also stated that this discovery is in contrast to our 
statement in the proposed rule that chytrid fungal disease does not 
seem to be plaguing remaining mountain yellow-legged frog populations 
in southern California.
    Another peer reviewer stated that chytrid fungus does not seem to 
be a major issue concerning current frog populations because it 
presumably already caused an unknown, massive die-off of frog 
populations across southern California during the late 1960s and 1970s, 
resulting in small remnant populations that currently exist. However, 
it may still be eliminating frogs at some specific locations, such as 
the North Fork of the San Jacinto River below Mt. San Jacinto State 
Park.
    Our Response: At the time of writing the proposed rule, we were 
unaware that chytrid fungus was detected in mountain yellow-legged 
frogs in southern California. We do not have enough information at this 
time to determine the magnitude of impacts that chytrid has had or will 
have on frog populations in southern California. Nonetheless, because 
there is no information demonstrating the relationship between habitat 
features or quality and chytrid fungus, the information provided by the 
peer reviewer does not change the critical habitat designation.
    (4) Comment: One peer reviewer stated the critical habitat 
designation should include aquatic refugia as a primary constituent 
element (PCE) since we discuss it in the Primary Constituent Elements 
section under ``Cover or Shelter.''
    Our Response: We agree with the peer reviewer and have included 
aquatic refugia as a condition of PCE 1, which includes pools with bank 
overhangs, downfall logs or branches, and/or rocks, because it provides 
cover from predators. For more information, please see the Primary 
Constituent Elements section below.
    (5) Comment: One peer reviewer stated the critical habitat 
designation should provide more discussion on the role of canopy cover 
and habitat suitability and that there is a delicate and unknown 
balance between canopy cover and suitability of high-elevation habitat. 
In the San Jacinto Mountains, the canopy has become so extensive that 
it threatens the existence of the mountain yellow-legged frog. It is 
critical that suitable habitat be protected and it may be necessary to 
manipulate the canopy to open up the habitat.
    Our Response: In general, information on the effects of canopy 
cover on habitat suitability is limited. Our discussion on canopy cover 
in the Primary Constituent Elements section below was based only on 
data values reported from a USGS report on mountain yellow-legged frog 
populations in southern California (Backlin et al. 2004). We agree with 
the reviewer that canopy cover may affect habitat suitability and have 
discussed this in our Special Management section below by stating that 
it may be necessary in some of the critical habitat units to reduce 
canopy cover to make habitat more suitable for this species. However, 
without more specific information, we are unable to address this issue 
more thoroughly in this critical habitat designation.
    (6) Comment: One peer reviewer approved of our use and application 
of upland frog movement data from Sierra Nevada populations to southern 
California populations because it is difficult to obtain upland habitat 
use information from mountain yellow-legged frog populations in 
southern California. Therefore, the interpretations made in the 
proposed rule to designate critical habitat are reasonable.
    Our Response: We appreciate the concurrence with our methods for 
determining the criteria used to identify critical habitat. For more 
information, please see the Criteria Used To Identify Critical Habitat 
section below.
    (7) Comment: Two peer reviewers questioned the methods used to 
calculate stream-width and length for ``occupied'' habitat. One of the 
reviewers questioned the movement distance (4,905 feet (ft) (1,495 
meters (m)) that the Service used in the proposed critical habitat rule 
to estimate the length of occupied stream if there is suitable habitat 
that extends beyond this distance. The other reviewer questioned why 
the Service discounted the possibility that the maximum distance moved 
was crucial to the mountain yellow-legged frog's survival and 
questioned whether there were enough downstream habitats to provide for 
refugia during droughts and for connectivity between streams. The 
reviewer suggested redefining areas containing essential features to 
capture 11,745 ft (3,580 m) upstream and downstream from occurrence 
locations based on data from other studies, as well as 1,378 ft (420 m) 
from the centerline of streams for upland movements. The reviewer also 
questioned whether there had been efforts made to quantify frog habitat 
use and movement during specific breeding, feeding, and overwintering 
periods, including off-stream habitats.
    Our Response: In general, information on mountain yellow-legged 
frog movements in southern California is extremely limited. Our 
discussion on mountain yellow-legged frog movements was based on the 
maximum distance moved by an individual mountain yellow-legged frog in 
the San Bernardino Mountains in southern California (Backlin et al. 
2004). We did not include the larger dataset on frog movements in the 
Sierra Nevada mountains because of the different habitat 
characteristics associated with mountain yellow-legged frogs in the 
Sierra Nevada (e.g., lakes and higher elevation). However, we relied on 
data from the Sierra Nevada mountains to determine the width of 
riparian and upland habitats occupied by mountain yellow-legged frogs, 
because we did not have any such data from southern Californian 
mountain yellow-legged frogs. Although we recognize that suitable 
habitat may extend beyond the distances we used to determine critical 
habitat, we did not receive better information on a more appropriate 
distance measure to use for southern California mountain yellow-legged 
frogs. Finally, we are also unaware of any efforts to quantify mountain 
yellow-legged frog habitat use and movement during specific breeding, 
feeding, and overwintering periods, including off-stream habitats in 
southern California. For more information, please see the Criteria Used 
To Identify Critical Habitat section below.
    (8) Comment: One peer reviewer stated the proposed rule did not 
contain discussion on how the Service determined how much unoccupied 
habitat was essential for the conservation of the species. The peer 
reviewer suggested that more unoccupied areas may be essential for the 
conservation of the species.
    Our Response: We believe that we did provide a thorough discussion 
regarding the criteria that were used for identifying unoccupied 
streams in the proposed critical habitat rule published on September 
13, 2005 (70 FR 54106). Furthermore, we did not receive additional 
information that identified specific unoccupied areas, and rationale 
for those areas, that should be considered as critical habitat during 
the comment period for the proposed rule. For more information, please 
see the Criteria Used To Identify Critical Habitat section below.
    (9) Comment: Two peer reviewers questioned our use of a 1 to 4 year 
range for tadpole growth. One reviewer commented that since this was 
based on

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Sierra Nevada mountain yellow-legged frog populations, southern 
California frog populations living at much lower elevation would likely 
not require up to 4 years. The other reviewer stated that tadpole 
growth phase appeared to be around 2 years for southern California 
populations based on their experience.
    Our Response: At the time of writing the proposed rule, the best 
information available on tadpole growth was from Sierra Nevada mountain 
yellow-legged frog populations. We agree with the reviewer that this 
may have been an overestimate of the time it can take for tadpole 
growth. Based on peer reviewer comments, we have revised the discussion 
of the amount of time for tadpole growth by citing a period 1-2 years 
instead of up to 4 years (see section below titled Primary Constituent 
Elements for the Mountain Yellow-Legged Frog).
    (10) Comment: One peer reviewer questioned whether the values used 
for dissolved oxygen as a PCE were too narrow in range.
    Our Response: After reevaluating our interpretation of the 
available dissolved oxygen data, we agree with the reviewer that the 
dissolved oxygen values used as a PCE in the proposed rule may have 
represented too narrow a range to accurately describe habitat 
suitability for the mountain yellow-legged frog. We also believe that 
information on other water quality factors (water chemistry and 
temperature) were insufficient to accurately describe the complete 
range of values that may be necessary to maintain suitable habitat for 
mountain yellow-legged frogs. As a result, we have removed water 
quality as a PCE from the final critical habitat rule.
    (11) Comment: One peer reviewer stated the PCEs should also include 
intermittent stream reaches and tributaries to permanent streams 
because they are also used by mountain yellow-legged frogs.
    Our Response: Our process for capturing upland areas as critical 
habitat does include some parts of intermittent stream reaches and 
tributaries to the main stream reach identified as critical habitat. 
The peer reviewer did not provide substantial information indicating 
the significance of intermittent stream reaches to mountain yellow-
legged frogs. Therefore, we are unable to quantify the importance of 
this habitat type and have not expanded the boundaries of critical 
habitat to include additional intermittent stream reaches and 
tributaries to permanent streams. For more information on how we 
designated critical habitat, please see the Criteria Used To Identify 
Critical Habitat section below.
    (12) Comment: One peer reviewer questioned whether there is any 
basis for using 3.1 miles (mi) (5 kilometers (km)) from nearby occupied 
streams as a criterion for choosing unoccupied sites.
    Our Response: In general, information on mountain yellow-legged 
frog dispersal movements in southern California is extremely limited. 
Our discussion on mountain yellow-legged frog movements was based on 
the best available data from a dispersal study in the Sierra Nevada 
Mountains, California (Knapp in litt. 2005). In this study, frogs were 
reported to disperse several kilometers and recolonize lakes following 
trout removal. Frogs were reported to move several kilometers along 
streams and across dry land. The data from this study were used to 
develop a dispersal function that was included in a population 
viability analysis. The analysis used a dispersal function of 2.5 mi (4 
km) and consistently produced frog distributions similar to those 
actually found in the field. We recognize that the environment in the 
Sierra Nevada mountains is different from the frog habitat in the 
southern California mountains. However, since this is the best 
information available for this species on dispersal behavior, we used 
it as one of the criteria for selecting unoccupied critical habitat 
areas. In the proposed rule, we erroneously cited a dispersal distance 
of 3.1 mi (5 km). The distance has been changed to 2.5 mi (4 km) in 
this final critical habitat rule (see section titled Stream Reaches Not 
Currently Known to Be Occupied for a more detailed discussion).
    (13) Comment: One peer reviewer questioned why the proposed rule 
did not include trout predation, one of the largest threats to frog 
populations, in the Special Management Considerations section and 
whether there are efforts to remove non-native trout from occupied 
mountain yellow-legged frog habitat.
    Our Response: We included threats that may require special 
management considerations and that have an effect on primary 
constituent elements. The threat of trout predation has the potential 
to affect the survival of mountain yellow-legged frogs but does not 
affect habitat features. We recognize that non-native trout predation 
is a major threat to the recovery of the mountain yellow-legged frog 
and encourage programs to remove introduced trout from streams where 
frog recovery is designated. The critical habitat rule does not 
authorize management actions; however, we strongly encourage trout 
removal for adequate frog conservation. We discussed one previous trout 
removal action in subunit 1C (Little Rock Creek) in the Unit 
Descriptions section.
    (14) Comment: One peer reviewer questioned whether Riverside County 
can actually purchase and conserve all 141 ac of private land that was 
excluded from critical habitat based on the lands inclusion within the 
Western Riverside County Multiple Species Habitat Conservation Plan 
(MSHCP) as stated in the proposed critical habitat rule.
    Our Response: No areas containing features essential to the 
conservation of the mountain yellow-legged frog are within lands 
(Additional Reserve Lands) that are to be purchased and conserved by 
Riverside County under their Western Riverside County MSHCP. We 
mistakenly presented this in the proposed critical habitat rule (70 FR 
54106) in our discussion regarding the exclusion of non-Federal lands 
that are covered under the MSHCP. We are still excluding these lands 
because of conservation measures provided for the mountain yellow-
legged frog from the MSHCP's Additional Survey Needs and Procedures 
policy (see Relationship of Critical Habitat to Approved Habitat 
Conservation Plans section for a more detailed discussion).
    (15) Comment: One peer reviewer stated the two-striped garter snake 
(Thamnophis hammondii) and raccoons (Procyon lotor) should be included 
as potential predators in the Primary Constituent Elements section 
within the discussion on Cover or Shelter.
    Our Response: A broad range of terrestrial taxa have been observed 
as predators of mountain yellow-legged frogs, including several species 
of birds, snakes, and mammals (Jennings et al. 1992; Mathews et al. 
2002; Mullally and Cunningham 1956). We have added the two predators 
mentioned by the peer reviewer to the list of potential predators from 
which mountain yellow-legged frogs would try to seek cover (see Primary 
Constituent Elements section within the discussion on Cover or Shelter 
for a more detailed discussion).
    (16) Comment: One peer reviewer stated that the critical habitat 
rule should include bedrock just underneath the surface of the water as 
another type of sunning post as a primary constituent element.
    Our Response: We appreciate the clarification on sunning post 
features and have added bedrock just underneath the surface of the 
water as another important potential type of sunning post that mountain 
yellow-legged frogs may utilize to our description of PCE 1. For more

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information, please see the Primary Constituent Elements section below.
    (17) Comment: One peer reviewer questioned whether enforcement 
activities by the Service were a part of the Western Riverside County 
MSHCP, and if so, then the justification for not including non-Federal 
lands within the MSHCP is justified. If not, then the peer reviewer 
questioned whether the level of protection under the MSHCP is 
consistent with that of the critical habitat proposal.
    Our Response: The Service issued a single incidental take permit 
pursuant to section 10(a)(1)(B) of the Act as well as entered into an 
Implementing Agreement with the 22 Permittees of the MSHCP. The Service 
is responsible for overseeing the Permittees' compliance with the 
permit and Implementing Agreement. When implemented, we expect the 
MSHCP will provide substantial protection of the PCEs and special 
management of essential habitat features for the mountain yellow-legged 
frog on MSHCP conservation lands. This level of management for the 
mountain yellow-legged frog on private lands by the MSHCP is greater 
than a critical habitat designation (see section titled Relationship of 
Critical Habitat to Approved Habitat Conservation Plans (HCPs)--
Exclusion Under Section 4(b)(2) of the Act for a more detailed 
discussion). Therefore, we agree with the commenter that excluding non-
Federal lands within the MSHCP from the critical habitat designation is 
justified.
    (18) Comment: One peer reviewer stated the critical habitat rule 
should include fire control activities as a Federal activity that may 
adversely affect critical habitat because of threats of water removal 
from streams, dropping fire retardant on streams or frogs, disease and 
exotic predator transport from clothing or footwear of fire fighters 
and water drops, respectively.
    Our Response: We have included fire control activities under 
Federal activities that may adversely affect critical habitat. For more 
information, please see the Effects of Critical Habitat Designation 
section below.

General Comments

Comments Related to Procedural and Legal Compliance
    (19) Comment: One commenter stated that critical habitat should not 
be designated within the Western Riverside County MSHCP plan area 
because the mountain yellow-legged frog is one of the listed species 
covered under the MSHCP. The plan was approved by the County of 
Riverside and 14 cities, and issued a Section 10(a) permit by the 
Service in 2004.
    Our Response: We agree with the commenter and have excluded from 
critical habitat all non-Federal lands containing features essential to 
the conservation of the mountain yellow-legged frog within the MSHCP 
Plan Area. However, we are designating Federal lands managed by the 
United States Forest Service (USFS) within the MSHCP Plan Area as 
critical habitat because they are not a permittee under the section 
10(a)(1)(B) permit for the MSHCP. For more information, please see 
Exclusion Under Section 4(b)(2) of the Act section below.
    (20) Comment: One commenter stated that critical habitat should not 
be designated on Federal lands in the Angeles and San Bernardino 
National Forest because designating critical habitat for species 
already on the endangered species list provides little added 
conservation benefit to the species. This commenter also stated the 
U.S. Army Corps of Engineers' (Corps) current involvement in an 
ecological restoration project in the San Bernardino Mountains has the 
potential to be within the downstream portions of watersheds in which 
critical habitat is proposed for the mountain yellow-legged frog, 
although none of the critical habitat areas is actually within the 
Corps' study boundary.
    Our Response: We are obligated under the Act to designate critical 
habitat on the basis of the best scientific data available and after 
taking into consideration the economic impact, and any other relevant 
impact, of designating an area as critical habitat. The Secretary may 
exclude an area if the benefits of exclusion outweigh the benefits of 
inclusion unless the Secretary determines that such exclusion will 
result in the extinction of the species.
    We examined the USFS's Revised Land and Resource Management Plans 
for the Four Southern California Forests, California (Forest Plan) that 
was approved in September 2005 and the Service's biological opinion 
that was issued on the Forest Plan on September 15, 2005. At issue were 
the effects of the Forest Plan and ongoing activities on USFS lands on 
federally-listed species, including the mountain yellow-legged frog. 
The goal of the Forest Plan is to describe a strategic direction for 
the management of the national forests over the next 10 to 15 years. 
The Forest Plan does not make any decisions regarding USFS site-
specific project proposals for implementing the land management plans 
nor do they compel managers to implement any specific conservation 
activities. The Forest Plan also divides the national forests into 
several ``Land Use Zones'', including Developed Area Interface, Back 
Country, Back Country Motorized Use Restricted, Back Country Non-
Motorized, Critical Biological, Recommended Wilderness, Existing 
Wilderness, and Experimental Forest. The land use zones were designed 
to describe the type of anticipated and allowable public use or 
administrative activities.
    During the proposed critical habitat rulemaking process, we 
coordinated with staff from both the Angeles and San Bernardino 
National Forests to seek their input on the best areas to designate 
critical habitat on their lands that will contribute to the recovery of 
the mountain yellow-legged frog. Due to the amount of unoccupied 
critical habitat areas and the precarious status of existing 
populations, we determined that the benefit of including USFS lands as 
critical habitat are significant because this will help maintain the 
Service's role in reviewing potential future impacts to areas that are 
important for the survival and recovery of mountain yellow-legged frog 
populations. Our decision to designate critical habitat on USFS lands 
was supported in a public comment letter from the Angeles National 
Forest regarding critical habitat on their lands. We do not have 
information indicating that the benefits of excluding Federal lands 
within the National Forests will outweigh the benefits of including 
these lands.
    As for the Corps' ecological restoration project, we are not aware 
of the specifics of this project. Federal projects that may affect 
critical habitat require consultation with the Service. However, we 
would hope that an ecological restoration project would provide long-
term benefits to the mountain yellow-legged frog and its habitat.
    (21) Comment: One commenter stated that they did not support USFS 
management practices that may be detrimental to the mountain yellow-
legged frog, such as pesticide use, vegetation removal agents, and 
prescribed burning.
    Our Response: We appreciate the commenter's concerns regarding 
threats to the mountain yellow-legged frog. These threats are addressed 
in the Special Management Considerations section as well as in the 
Effects of Critical Habitat Designation sections below.
    (22) Comment: One commenter stated that they are opposed to the 
overzealous land grabbing by the County of

[[Page 54349]]

Riverside for the protection of the mountain yellow-legged frog.
    Our Response: This issue is beyond the scope of this critical 
habitat rule. The designation of critical habitat does not dictate 
decisions regarding land acquisition, use, or management practices.
Comments Related to the Draft Economic Analysis (DEA)
    (23) Comment: One commenter stated that attributing costs 
associated with protection measures for the mountain yellow-legged frog 
(i.e., loss of recreation, fishing, hiking, camping, and rock climbing) 
on USFS lands was wrong and misleading because these would have been 
done for the conservation of the species, not necessarily because of 
critical habitat designation. For example, the North Fork of the San 
Jacinto River and City Creek on the San Bernardino National Forest was 
already closed to public recreation use in the stream prior to this 
critical habitat designation.
    Our Response: We recognize that the USFS has already been 
conducting conservation measures for the mountain yellow-legged frog 
prior to this designation. The DEA identifies those economic activities 
believed to most likely threaten the listed species and its habitat 
and, where possible, quantifies the economic impact to avoid, mitigate, 
or compensate for such threats within the boundaries of the critical 
habitat designation. In instances where critical habitat is being 
proposed after a species is listed, some future impacts may be 
unavoidable, regardless of the final designation and exclusions under 
4(b)(2). However, due to the difficulty in making a credible 
distinction between listing and critical habitat effects within 
critical habitat boundaries, the analysis in the DEA considers all 
future conservation-related impacts to be co-extensive with the 
designation. Inclusion of co-extensive impacts in the DEA complies with 
instruction by the United States Court of Appeals in 2001 for the 
Service to conduct a full analysis of all of the economic impacts or 
the proposed critical habitat designation, regardless of whether those 
impacts are attributable co-extensively to other causes (New Mexico 
Cattle Growers Association v. United States Fish and Wildlife Service, 
248 F.3d 1277 (10th Cir. 2001)).

Summary of Changes From Proposed Rule

    In preparing the final critical habitat designation for the 
mountain-yellow-legged frog, we reviewed and considered comments from 
the public and peer reviewers on the proposed designation of critical 
habitat published on September 13, 2005 (70 FR 54106) and public 
comments on the draft economic analysis published on July 3, 2006 (71 
FR 37881). As a result of comments received on the proposed rule and 
the DEA, and a reevaluation of the proposed critical habitat 
boundaries, we made changes to our proposed designation, as follows:
    (1) We added an additional feature (rocks just beneath the surface 
of the water for sunning posts) to PCE 1 based on one peer reviewer's 
comment.
    (2) We added aquatic refugia as another feature to PCE 1 based on 
two peer reviewer comments.
    (3) After a reevaluation of the existing information on water 
quality (i.e., pH, dissolved oxygen, and water temperature) and comment 
from a peer reviewer on our use of a narrow range of water quality 
parameters to describe water quality as a PCE, we determined that there 
was insufficient information on water quality to provide an accurate 
range of water quality values that describes suitable frog habitat. 
Therefore, we removed water quality as a PCE (see Comment 10 
above for a more detailed discussion).
    (4) We changed our determination of the occupancy status of Day 
Canyon, East Fork of Barton Creek, and Indian Creek at Hall Canyon from 
currently occupied to currently unoccupied and not occupied at the time 
of listing based on a reevaluation of existing information and 
discussions with biologists that have surveyed these sites. Mountain 
yellow-legged frogs have not been detected in any of these streams 
since the mid-1990s, but not all the stream reaches in Day Canyon and 
Indian Creek at Hall Canyon have been surveyed. Without recent 
documentation that these streams are known to be occupied, we believe 
this change appropriately reflects the species' current status.
    (5) We corrected the dispersal distance used in the section titled 
Criteria Used to Identify Critical Habitat from 3.1 mi (5 km) to 2.5 mi 
(4 km). This information is based on the best available data on 
mountain yellow-legged frog movements from a dispersal study conducted 
in the Sierra Nevada Mountains, California (Knapp in litt. 2005) (see 
Comment 12 above for a more detailed discussion).

Critical Habitat

    Critical habitat is defined in section 3 of the Act as--(i) 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 (I) Essential to the conservation 
of the species and (II) that may require special management 
considerations or protection; and (ii) 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 
to use and the use of all methods and procedures which are necessary to 
bring any endangered species or threatened species to the point at 
which the measures provided pursuant to the Act are no longer 
necessary. Such methods and procedures include, but are not limited to, 
all activities associated with scientific resources management such as 
research, census, law enforcement, habitat acquisition and maintenance, 
propagation, live trapping, and transplantation, and, in the 
extraordinary case where population pressures within a given ecosystem 
cannot be otherwise relieved, may include regulated taking.
    Critical habitat receives protection under section 7 of the Act 
through the prohibition against destruction or adverse modification of 
critical habitat with regard to actions carried out, funded, or 
authorized by a Federal agency. Section 7 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 government or public access to private 
lands. Section 7 is a purely protective measure and does not require 
implementation of restoration, recovery, or enhancement measures.
    To be included in a critical habitat designation, the habitat 
within the area occupied by the species 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 (i.e., areas on which are found the primary constituent 
elements, as defined at 50 CFR 424.12(b)).
    Habitat occupied at the time of listing may be included in critical 
habitat only if the essential features thereon may require special 
management considerations or protection. Thus, we do not include areas 
where existing management is sufficient to conserve the species. (As 
discussed below, such areas may also be excluded from critical habitat 
pursuant to section 4(b)(2) of the Act). In areas outside the 
geographical

[[Page 54350]]

area occupied by the species at the time of listing, when the best 
available scientific data do not demonstrate that the conservation 
needs of the species require additional areas, we will not designate 
critical habitat within those areas. An area currently occupied by the 
species but not known to be occupied at the time of listing will 
likely, but not always, be essential to the conservation of the species 
and, therefore, typically be included in the critical habitat 
designation.
    The Service's Policy on Information Standards Under the Endangered 
Species Act, published in the Federal Register on July 1, 1994 (59 FR 
34271), and Section 515 of the Treasury and General Government 
Appropriations Act for Fiscal Year 2001 (P.L. 106-554; H.R. 5658) and 
the associated Information Quality Guidelines issued by the Service, 
provide criteria, establish procedures, and provide guidance to ensure 
that decisions made by the Service represent the best scientific data 
available. They require Service 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 determining which 
areas are critical habitat, a primary source of information is 
generally the listing package for the species. Additional information 
sources 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. All 
information is used in accordance with the provisions of Section 515 of 
the Treasury and General Government Appropriations Act for Fiscal Year 
2001 (P.L. 106-554; H.R. 5658) and the associated Information Quality 
Guidelines issued by the Service.
    Section 4 of the Act requires that we designate critical habitat on 
the basis of the best scientific data available. Habitat is often 
dynamic, and species may move from one area to another over time. 
Furthermore, we recognize that designation of critical habitat may not 
include all of the habitat areas that may eventually be determined to 
be necessary for the recovery of the species. For these reasons, 
critical habitat designations do not signal that habitat outside the 
designation is unimportant or may not be required for recovery.
    Areas that support populations, but are outside the critical 
habitat designation, will continue to be subject to conservation 
actions implemented under section 7(a)(1) of the Act and to the 
regulatory protections afforded by the section 7(a)(2) jeopardy 
standard, as determined on the basis of the best available information 
at the time of the 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, 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)(1)(A) of the Act, we use the best 
scientific data available to determine areas that contain the features 
essential to the conservation of the mountain yellow-legged frog. This 
includes information from the proposed listing rule (64 FR 71714), 
final listing rule (67 FR 44382), proposed critical habitat rule (70 FR 
54106), site visits, soil and species map coverages, and data compiled 
in the California Natural Diversity Database (CNDDB). We also reviewed 
available information regarding the ecology, natural history, and 
habitat requirements of the species. This material included information 
and data in reports submitted during section 7 consultations, research 
published in peer-reviewed articles and technical reports by the USGS 
and the USFS, and regional GIS coverages.

Primary Constituent Elements

    In accordance with section 3(5)(A)(i) of the Act and regulations at 
50 CFR 424.12, in determining which areas to designate as critical 
habitat, we consider those physical and biological features (PCEs) that 
are essential to the conservation of the species, and within areas 
occupied by the species at the time of listing, that may require 
special management considerations or protection. These include, but are 
not limited to space for individual and population growth and for 
normal behavior; food, water, air, light, minerals, or other 
nutritional or physiological requirements; cover or shelter; sites for 
breeding, reproduction, and rearing (or development) of offspring; and 
habitats that are protected from disturbance or are representative of 
the historical geographical and ecological distributions of a species.
    The specific primary constituent elements required for the mountain 
yellow-legged frog are derived from the biological needs of the 
mountain yellow-legged frog as described below and in the proposed 
critical habitat designation published in the Federal Register on 
September 13, 2005 (70 FR 54106).

Space for Individual and Population Growth and Normal Behavior

    Mountain yellow-legged frogs are a highly aquatic, cryptic, diurnal 
species that occupy mountain streams which have cool waters and 
originate from springs and snowmelt (Jennings and Hayes 1994a, b). 
Mountain yellow-legged frogs are most often found in creeks with 
permanent water in at least some portion of the reach. Mountain yellow-
legged frogs also utilize streams, rivers, perennial creeks, permanent 
plunge pools within intermittent creeks and pools, and their associated 
riparian and upland habitat (Mullally 1959, Backlin et al. 2004). 
Backlin et al. (2004) reported creeks with occupied mountain yellow-
legged frog populations were generally narrow, averaging from 3 to 10 
ft (1 to 3 m) wide, with associated riparian zone widths ranging from 
26 to 82 ft (8 to 25 m), with canyon walls typically rising steeply on 
either side. They also reported stream reach lengths containing 
mountain yellow-legged frog populations varied from approximately 820 
ft (250 m) in Dark Canyon, to greater than 16,404 ft (5,000 m) in East 
Fork, City Creek. Backlin et al. (2004) also reported that pools were 
typically 3 to 32 ft (1 to 10 m) long, 2 to 23 ft (0.5 to 7 m) wide, 
0.4 to 180 inches (in) (1 to 180 cm) deep, and typically had some type 
of structure in the form bank overhangs, downfall sticks, and/or rocks 
that could function as refugia, but there was minimal aquatic 
vegetation. Mountain yellow-legged frogs have been noted to inhabit 
creeks varying in type from high gradient with rocky courses to low 
gradient with marshy margins and sod banks (Mullally 1959). Creeks such 
as those with permanent water sources and their associated riparian and 
upland habitat (PCE 1) provide breeding sites, foraging grounds, and 
shelter for individual and population growth and normal behavior. They 
also provide for perennial flows needed for egg-laying and tadpole 
growth and survival.

Food, Water, Air, Light, or Other Nutritional or Physiological 
Requirements

    Mountain yellow-legged frogs appear to be principally 
insectivorous, feeding on a wide variety of invertebrates, including 
beetles (Coleoptera), ants

[[Page 54351]]

(Formididae), bees (Apoidea), wasps (Hymenoptera), flies (Diptera), 
true bugs (Hemiptera), and dragonflies (Odonata) (Long 1970). 
Terrestrial insects and adult stages of aquatic insects may be the 
preferred food for adult mountain yellow-legged frogs (Bradford 1983); 
larger frogs consume more aquatic true bugs likely because of their 
more aquatic behavior (Jennings and Hays 1994a). Some predation of 
tadpoles by adult mountain yellow-legged frogs appears possible as 
evidenced in Sierra Nevada populations (Mathews and Pope 1999).
    The riparian zone, with the associated vegetation canopy (PCE 2), 
is necessary to maintain the prey base needed for the nutritional 
requirements of the mountain yellow-legged frog. Larvae graze on algae 
and diatoms in the silt along rocky bottoms in streams (Zeiner et al. 
1988). An open or semi-open canopy of riparian vegetation (canopy 
overstory not exceeding 85 percent, Backlin et al. 2004) is needed to 
ensure that adequate sunlight reaches the stream to allow for basking 
behavior and for photosynthesis by benthic algae and diatoms that are 
food resources for larval mountain yellow-legged frog.

Cover or Shelter

    Mountain yellow-legged frogs are preyed upon by the western 
terrestrial garter snake (Thamnophis elegans), two-striped garter 
snake, Brewer's blackbird (Euphagus cyanocephalus), Clark's nutcrackers 
(Nucifraga columbiana), raccoons, and coyotes (Canis latrans) (Jennings 
et al. 1992; Jennings in litt. 2005; Mathews et al. 2002; Mullally and 
Cunningham 1956; USFS 2002). Pools with bank overhangs, downfall logs 
or branches, and/or rocks (PCEs 1 and 2) provide cover from predators 
for mountain yellow-legged frogs.

Sites for Breeding, Reproduction, and Rearing of Offspring

    In southern California, the mountain yellow-legged frog occupies 
streams in the chaparral belt (Zweifel 1955), and cool and cold, rocky, 
mountain watercourses shaded by trees, rocks, and other shelter, where 
the flow comes from springs and snowmelt (Jennings and Hayes 1994b) 
(PCEs 1 and 2). White alders (Alnus rhombifolia), willows, sycamore, 
cottonwoods, conifers, and maples dominate the mountain yellow-legged 
frog's non-aquatic habitat (Jennings and Hayes 1994b; Backlin et al. 
2004). Open gravel banks and rocks projecting above or just underneath 
the surface of the water may provide sunning posts (Zweifel 1955; 
Jennings in litt. 2005). Many of the streams in which mountain yellow-
legged frogs occurred historically and currently occupy have a 
relatively steep gradient and large boulders in the stream beds 
(Stebbins 1951). Although knowledge pertaining to the specific habitat 
requirements of mountain yellow-legged frogs in southern California is 
limited, the presence of water year-round is known to be necessary for 
both reproduction and for hydration of juveniles and adults (Vredenburg 
et al. 2005). Individuals may, however, aestivate during especially dry 
periods of late summer (Mullally 1959). In southern California, 
mountain yellow-legged frogs historically ranged from 1,214 to 7,546 ft 
(370 to 2,300 m) in elevation (Jennings and Hayes 1994a, 1994b).

Primary Constituent Elements for the Mountain Yellow-Legged Frog

    Pursuant to our regulations, we are required to identify the known 
physical and biological features (PCEs) essential to the conservation 
of the mountain yellow-legged frog. Areas designated as critical 
habitat for the mountain yellow-legged frog contain both occupied and 
unoccupied streams and riparian areas within the species' historical 
geographic range, and contain sufficient PCEs to support at least one 
life history function. In identifying PCEs, we used the best available 
scientific data available. Although the physical ranges described below 
may not capture all of the variability that is inherent in natural 
systems, these ranges best represent the physical and biological 
features essential to the conservation of the mountain yellow-legged 
frog in the occupied areas designated as critical habitat. In order to 
conserve this species, we believe it is necessary to designate critical 
habitat in areas currently unoccupied by the species. For more 
information, please see the Criteria Used to Identify Critical Habitat 
and Unit Descriptions sections below for further discussion of 
unoccupied habitat.
    Based on our current knowledge of the life history, biology, and 
ecology of the species and the requirements of the habitat to sustain 
the essential life history functions of the species, we have determined 
that the mountain yellow-legged frog's PCEs are:

    (1) Water source(s) found between 1,214 to 7,546 feet (370 to 
2,300 meter) in elevation that are permanent. Water sources include, 
but are not limited to, streams, rivers, perennial creeks (or 
permanent plunge pools within intermittent creeks), pools (i.e., a 
body of impounded water that is contained above a natural dam) and 
other forms of aquatic habitat. The water source should maintain a 
natural flow pattern including periodic natural flooding. Aquatic 
habitats that are used by mountain yellow-legged frog for breeding 
purposes must maintain water during the entire tadpole growth phase, 
which can last for up to 2 years. During periods of drought, or less 
than average rainfall, these breeding sites may not hold water long 
enough for individuals to complete metamorphosis, but they would 
still be considered essential breeding habitat in wetter years. 
Further, the aquatic includes:
    a. Bank and pool substrates consisting of varying percentages of 
soil or silt, sand, gravel cobble, rock, and boulders;
    b. Open gravel banks and rocks projecting above or just beneath 
the surface of the water for sunning posts;
    c. Aquatic refugia, including pools with bank overhangs, 
downfall logs or branches, and/or rocks to provide cover from 
predators; and
    d. Streams or stream reaches between known occupied sites that 
can function as corridors for movement between aquatic habitats used 
as breeding and/or foraging sites.
    (2) Riparian habitat and upland vegetation (e.g., ponderosa 
pine, montane hardwood-conifer, montane riparian woodlands, and 
chaparral) extending 262 feet (80 meters) from each side of the 
centerline of each identified stream and its tributaries, that 
provides areas for feeding and movement of mountain yellow-legged 
frog, with a canopy overstory not exceeding 85 percent that allows 
sunlight to reach the stream and thereby provide basking areas for 
the species.

    This designation is designed for the conservation of PCEs necessary 
to support the life history functions of the mountain yellow-legged 
frog. Because not all life history functions require all the PCEs, not 
all areas designated as critical habitat will contain all the PCEs.
    Each of the areas designated in this rule have been determined to 
contain sufficient PCEs to provide for one or more of the life history 
functions of the mountain yellow-legged frog. In some cases, the PCEs 
exist as a result of ongoing Federal actions. As a result, ongoing 
Federal actions at the time of designation will be included in the 
baseline in any consultation conducted subsequent to this designation.

Criteria Used To Identify Critical Habitat

    We are designating critical habitat in areas within the 
geographical area occupied by the species at the time of listing in 
2002, as well as some specific unoccupied areas outside the 
geographical area occupied by the species at the time of listing, but 
were historically occupied, because we have determined that such areas 
are essential for the conservation of the species.

Stream Reaches Occupied at the Time of Listing

    We have defined occupied critical habitat as: (a) Those streams 
known to

[[Page 54352]]

be occupied by the mountain yellow-legged frog at the time of listing 
in 2002; (b) the riparian, upland, and aquatic habitats 262 ft (80 m) 
from the centerline of the stream including tributaries; and (c) 
aquatic habitats within 4,905 ft (1,495 m) upstream from the upstream-
most occurrence and 4,905 ft (1,495 m) downstream from the downstream-
most occurrence on the main stem of the river or creek known to be 
occupied, including any tributary that flows into it (see the following 
sections for explanation of these values). We used information from the 
proposed and final listing rules, reports prepared by the USGS, the 
USFS, the California Department of Fish and Game (CDFG), the CNDDB, 
researchers, and consultants to identify the specific locations 
occupied by the southern California mountain yellow-legged frog at the 
time of listing. All occurrence records dating from 2002 of mountain 
yellow-legged frogs were plotted on maps in GIS as points and polygons.
    The currently occupied habitat for the mountain yellow-legged frog 
is highly limited and isolated. Population estimates are all extremely 
low, with no stream having an estimated population size exceeding 100 
breeding adults, and an overall total estimate of approximately 183 
adults surviving in 2003 (including City Creek, East Fork; Backlin et 
al. 2004). The mountain yellow-legged frog is at a high risk of 
extinction and is highly susceptible to stochastic events (Backlin et 
al. 2004). We have determined that all occupied areas contain features 
essential to the conservation of the species and are either designated 
as critical habitat or are excluded from designation pursuant to 
section 4(b)(2) of the Act.

Stream Reaches Unoccupied at the Time of Listing

    The streams not known to be currently occupied that are being 
designated as critical habitat were all historically occupied, and the 
designation of these areas as critical habitat will decrease the degree 
of fragmentation within the current geographic distribution of the 
mountain yellow-legged frog. We believe that the designation of these 
additional areas not known to be currently occupied by the mountain 
yellow-legged frog is essential for the conservation of the species 
because:
    (1) The current, overall population size of the mountain yellow-
legged frog is extremely small, and it must increase in order to insure 
long-term survival of this species in southern California (cf. Backlin 
et al. 2004). While the occupied units provide habitat for current 
populations, additional units will provide habitat for population 
augmentation either through natural means, or by re-introduction. Such 
population augmentation in the additional subunits may serve to 
decrease the risk of extinction of the species through stochastic 
events, such as fires or disease, as the current, isolated populations 
are each at high risk of extirpation from such stochastic events 
(Backlin et al. 2004), particularly because of their small sizes and 
restricted ranges;
    (2) Population augmentation either through natural means or by re-
introduction into the additional subunits may increase the viability of 
the occupied subunits as well as the existence of the mountain yellow-
legged frog in southern California as a whole (i.e., increase the 
likelihood of persistence at the local population level and of this DPS 
range-wide);
    (3) Additional subunits will serve to decrease the degree of 
fragmentation of the current geographic distribution of the mountain 
yellow-legged frog within each of the three mountain ranges (i.e., 
increase connectivity between streams that are known to be currently 
occupied);
    (4) Additional subunits are designated as critical habitat in areas 
occupied in the near past and located within the historical range of 
the species such that they will serve as corridors between currently 
occupied sites. Most of the unoccupied subunits lie within 0.9 to 2.5 
mi (1.5 to 4 km) of an occupied site; the only exception is Subunit 2C 
(in historically occupied Whitewater River). Although Subunit 2C is 
unlikely to serve as a corridor between currently oc