Endangered and Threatened Wildlife and Plants; 90-Day Finding on a Petition To List the Mt. Charleston Blue Butterfly as Threatened or Endangered, 29933-29941 [E7-10140]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 72, Number 103 (Wednesday, May 30, 2007)]
[Proposed Rules]
[Pages 29933-29941]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: E7-10140]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17


Endangered and Threatened Wildlife and Plants; 90-Day Finding on 
a Petition To List the Mt. Charleston Blue Butterfly as Threatened or 
Endangered

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 90-day petition finding.

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SUMMARY: We, the Fish and Wildlife Service (Service), announce a 90-day 
finding on a petition to list the Mt. Charleston blue butterfly 
(Icaricia shasta charlestonensis) as threatened or endangered under the 
Endangered Species Act of 1973, as amended (Act). We find that the 
petition presents substantial scientific or commercial information 
indicating that listing the Mt. Charleston blue butterfly may be 
warranted. Therefore, with the publication of this notice, we are 
initiating a status review of this subspecies, and we will issue a 12-
month finding to determine if the petitioned action is warranted. To 
ensure that the status review of the Mt. Charleston blue butterfly is 
comprehensive, we are soliciting scientific and commercial data 
regarding this subspecies. A determination on critical habitat will be 
made if and when a listing action is initiated for this subspecies.

DATES: The finding announced in the document was made on May 30, 2007. 
To be considered in the 12-month finding for this petition, comments 
and information should be submitted to us by July 30, 2007.

ADDRESSES: Data, information, comments, or questions concerning this 
petition and our finding should be submitted to the Field Supervisor, 
Nevada Fish and Wildlife Office, U.S. Fish and Wildlife Service, by 
mail at 4701 North Torrey Pines Drive, Las Vegas, NV, 89130, or by fax 
at (702) 515-5231. The petition is available at https://www.fws.gov/
nevada. The petition, supporting data, and comments will be available 
for public inspection, by appointment, during normal business hours at 
the Nevada Fish and Wildlife Office at the above address.

FOR FURTHER INFORMATION CONTACT: Robert D. Williams, Field Supervisor, 
Nevada Fish and Wildlife Office (see ADDRESSES) (telephone 702/515-
5230; facsimile 702/515-5231).

SUPPLEMENTARY INFORMATION:

Public Information Solicited

    When we make a finding that substantial information is presented to 
indicate that listing a species may be warranted, we are required to 
promptly commence a review of the status of the species. To ensure that 
the status review is complete and based on the best available 
scientific and commercial information, we are soliciting information on 
the Mt. Charleston blue butterfly. We request any additional 
information, comments, and suggestions from the public, other concerned 
governmental agencies, North American tribes, the scientific community, 
industry, or any other interested parties concerning the status of the 
Mt. Charleston blue butterfly. We are seeking information regarding the 
subspecies' historical and current status and distribution, its 
ecology, ongoing conservation measures for the subspecies and its 
habitat, and threats to the subspecies and its habitat.
    We will base our 12 month finding on a review of the best 
scientific and commercial information available, including all 
information received during the public comment period. If you wish to 
provide comments you may submit your comments and materials concerning 
this finding to the Field Supervisor, Nevada Fish and Wildlife Office 
(see ADDRESSES section). Please note that comments merely stating 
support or opposition to the actions under consideration without 
providing supporting information, although noted, will not be 
considered in making a determination, as section 4(b)(1)(A) of the Act 
directs that determinations as to whether any species is a threatened 
or endangered species shall be made ``solely on the basis of the best 
scientific and commercial data available.'' At the conclusion of the 
status review, we will issue the 12-month finding on the petition, as 
provided in section 4(b)(3)(B) of the Act.
    If you wish to comment or provide information, you may submit your 
comments and materials concerning this finding to the Field Supervisor 
(see ADDRESSES section). Before including your address, phone number, 
e-mail address, or other personal identifying information in your 
comment, you should be aware that your entire comment--including your 
personal identifying information--may be made publicly available at any 
time. While you can 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.

[[Page 29934]]

Background

    Section 4(b)(3)(A) of the Act requires that the U.S. Fish and 
Wildlife Service (Service) make a finding on whether a petition to 
list, delist, or reclassify a species presents substantial scientific 
or commercial information indicating that the petitioned action may be 
warranted. This finding is based on information contained in the 
petition and information otherwise available in our files at the time 
we make the finding. To the maximum extent practicable, we are to make 
this finding within 90 days of our receipt of the petition, and publish 
our notice of the finding promptly in the Federal Register.
    Our standard for substantial scientific or commercial information 
within the Code of Federal Regulations (CFR) with regard to a 90-day 
finding is ``that amount of information that would lead a reasonable 
person to believe that the measure proposed in the petition may be 
warranted'' (50 CFR 424.14(b)). If we find that substantial scientific 
or commercial information was presented, we are required to promptly 
commence a status review of this subspecies, if one has not already 
been initiated under our internal candidate assessment process.
    In making this finding, we relied on information provided by the 
petitioner and otherwise available in our files at the time of the 
petition review. We evaluated this information in accordance with 50 
CFR 424.14(b). The process of making a 90-day finding under section 
4(b)(3)(A) of the Act is based on a determination of whether the 
information in the petition meets the ``substantial scientific or 
commercial information'' threshold.
    On October 20, 2005, we received a petition from The Urban 
Wildlands Group, Inc., requesting to emergency-list the Mt. Charleston 
blue butterfly (Icaricia shasta charlestonensis) as a threatened or 
endangered species. In a letter dated April 20, 2006, we responded to 
the petitioner that our initial review did not indicate that an 
emergency situation existed, but that if conditions changed an 
emergency rule could be developed. This correspondence also indicated 
that funding was provided to address this petition in Fiscal Year 2006 
and that we anticipated making an initial finding early in Fiscal Year 
2007 as to whether or not the petition contained substantial 
information. The purpose of this finding is to determine whether or not 
the petition presented substantial information regarding the status of 
this subspecies within the context of the Act. The petition clearly 
identified itself as such and included the requisite identification 
information of the petitioner, as required in 50 CFR 424.14(a).

Species Information

    The Mt. Charleston blue butterfly is a distinctive subspecies of 
the wider ranging Shasta blue butterfly (Icaricia shasta), which is a 
member of Lycaenidae (little butterfly family). The subspecies is known 
only from the high elevations of the Spring Mountains, located 
approximately 25 miles (40 kilometers (km)) west of Las Vegas in Clark 
County, Nevada (Austin 1980, p. 20; Scott 1986, p. 410).
    Within Icaricia shasta there are six subspecies: I. s. calchas, I. 
s. shasta, I. s. minnehaha, I. s. charlestonensis, I. s. pallidissima, 
and I. s. pitkinensis (Scott 1986, p. 410; Murphy 2006, p. 3). The 
first mention of I. s. charlestonensis as a unique taxon was in 1928 by 
Garth, who recognized it as distinct from the species shasta (Austin 
1980, p. 20). Howe in 1975 described specimens from the Spring 
Mountains as I. s. shasta form comstocki (Austin 1980, p. 20). However, 
in 1976, Ferris placed the subspecies into the wider ranging I. s. 
minnehaha (Austin 1980, p. 20). Finally, Austin (1980) asserted that 
Ferris had not included populations from the Sierra Nevada in his 
study, and in light of the geographic isolation and distinctiveness of 
the Spring Mountains shasta population, and the presence of at least 
three other well defined races of butterflies endemic to the area, it 
was appropriate to name this population as the individual subspecies 
charlestonensis (Austin 1980, p. 20). This name and subspecies 
classification has been retained in the most recent treatments of 
butterfly taxonomy (Opler and Warren 2002, p. 79).
    The wing span of Icaricia shasta is \3/4\ to 1 inch (19 to 26 
millimeters (mm)) (Opler 1999, p. 251). Males and females of Icaricia 
shasta are dimorphic. The upperside of males is dark to dull iridescent 
blue, and females are brown with a blue overlay. The subspecies has a 
discal black spot on the forewing and a row of submarginal black spots 
on the hindwing. The underside is gray, with a pattern of black spots, 
brown blotches, and pale wing veins to give it a mottled appearance. 
The underside of the hindwing has an inconspicuous band of submarginal 
metallic spots (Opler 1999, p. 251). Based on morphology, I. s. 
charlestonensis appears to be most closely related to the Great Basin 
populations of I. s. minnehaha (Austin 1980, p. 23) and can be 
distinguished from I. s. minnehaha by sharper and blacker post medial 
spots on the underside of the hindwing (Scott 1986, p. 410).
    Weiss et al. (1997, pp. 10-11) describe the natural habitat for the 
Mt. Charleston blue as relatively flat ridgelines above 8,202 feet 
(2,500 meters); however, isolated individuals have been observed as low 
as 6,562 feet (2,000 meters). Like many butterfly species, the Mt. 
Charleston blue butterfly is dependent on plants both during larval 
development (larval host plants) and the adult butterfly flight period 
(nectar plants). The butterfly requires open habitats that support 
Torrey's milkvetch (Astragalus calycosus var. mancus), the only known 
larval host plant for the subspecies (Weiss et al. 1994, p. 3; Weiss et 
al. 1997, p. 10). Torrey's milkvetch and Clokey fleabane (Erigeron 
clokeyi) are the primary nectar plants for the subspecies; however, 
butterflies have also been observed nectaring on Lemmon's bitterweed 
(Hymenoxys lemmonii) and Aster sp. (Boyd 2005, p. 1; Weiss et al. 1994, 
p. 3). Torrey's milkvetch is a small, low growing, perennial herb that 
grows in open areas between 5,000-10,804 feet (1,524-3,293 meters) in 
subalpine, bristlecone, and mixed conifer vegetation communities of the 
Spring Mountains. Weiss et al. (1997, p. 31) describe favorable habitat 
for the Mt. Charleston blue butterfly as having high densities of 
Torrey's milkvetch, which exceed 10 plants per square meter. Good 
habitat contains relatively little grass cover and visible mineral soil 
(Boyd 2005, p. 1; Service 2006a, p. 1).
    The Mt. Charleston blue butterfly is generally presumed to diapause 
(period of suspended growth or development similar to hibernation) at 
the base of the larval host plant or in the surrounding substrate for 
at least one season (Boyd 2005, p. 1). The typical flight and breeding 
period for the butterfly is early July to mid-August with a peak in 
late July, although the species has been observed as early as mid-June 
and as late as mid-September (Austin 1980, p. 22; Boyd and Austin 1999, 
p. 17; Forest Service 2006a, p. 9). As with most butterflies, the Mt. 
Charleston blue butterfly typically flies during sunny conditions, 
which are particularly important for this subspecies given the cooler 
air temperatures at high elevations (Weiss et al. 1997, p. 31). 
Excessive winds also deter flight of most butterflies, although Weiss 
et al. (1997, p. 31) speculate this may not be a significant factor for 
the Mt. Charleston blue butterfly given its low-to-the-ground flight 
pattern. Other than observations by surveyors, little information is 
known regarding the

[[Page 29935]]

phenology of the Mt. Charleston blue butterfly, as the key determinants 
for the interactions between the butterfly's flight and breeding 
period, larval host plant, and environmental conditions have not been 
specifically studied. Observations indicate that above or below average 
precipitation, coupled with above or below average temperatures, 
influence the phenology of this subspecies (Weiss et al. 1997, pp. 2-3 
and 32; Boyd and Austin 1999, p. 8).
    Based on current and historic occurrences, the geographic range of 
the Mt. Charleston blue butterfly is on the east side of the Spring 
Mountains, centered on lands managed by the Forest Service in the 
Spring Mountains National Recreation Area of the Humboldt-Toiyabe 
National Forest within Kyle and Lee Canyons, Clark County, Nevada. The 
majority of the occurrences or observations are in the Lee Canyon area, 
with a few in Kyle Canyon. Table 1 identifies the fifteen separate 
current and historic locations of the Mt. Charleston blue butterfly 
that are documented in the petition or identified in the State of 
Nevada Natural Heritage Program database (The Urban Wildlands Group, 
Inc. 2005, pp. 1-3; Service 2006b, pp. 2-4).

    Table 1.--Locations or Occurrences of the Mt. Charleston Blue Butterfly since 1928 and the Status of the
                                           Butterfly at the Locations
----------------------------------------------------------------------------------------------------------------
                                            First/last
              Location name                time surveyed            Status                Primary references
                                            or observed
----------------------------------------------------------------------------------------------------------------
1. South Loop Trail, Kyle Canyon........       1995/2005  Presumed extant--core       Weiss et al. 1997.
                                                           colony.
2. LVSSR 1, Lee Canyon.........       1995/2005  Presumed extant--core       Weiss et al. 1997; Boyd
                                                           colony 1.                   and Austin 2002.
3. LVSSR 2, Lee Canyon.........       1963/2005  Presumed extant--core       Austin 1980; Weiss et al.
                                                           colony 1.                   1994; Weiss et al. 1997;
                                                                                       Boyd and Austin 2002.
4. Foxtail Camp, Lee Canyon.............       1998/1998  Presumed extant--ephemeral  Boyd and Austin 1999.
5. Youth Camp, Lee Canyon...............       1995/1995  Presumed extant--ephemeral  Weiss et al. 1997.
6. Gary Abbott, Lee Canyon..............       1995/1995  Presumed extant--ephemeral  Weiss et al. 1997.
7. LVSSR Parking, Lee Canyon............       1995/1995  Presumed extant--ephemeral  Weiss et al. 1997.
8. Mummy Spring, Kyle Canyon............       1995/1995  Presumed extant--ephemeral  Weiss et al. 1997.
                                                           2.
9. Lee Meadow, Lee Canyon...............       1965/1995  Presumed extant--ephemeral  Weiss et al. 1997.
10. Lee Canyon holotype.................       1963/1976  Presumed extirpated 2.....  Austin 1963; Austin 1980;
                                                                                       Weiss et al. 1997.
11. Cathedral Rock, Kyle Canyon.........       1972/1972  Presumed extirpated.......  Austin 1980; Weiss et al.
                                                                                       1997.
12. Kyle Canyon Ski Area................       1965/1972  Presumed extirpated 2.....  Austin 1980; Weiss et al.
                                                                                       1997.
13. Old Town, Kyle Canyon...............     1970s/1970s  Presumed extirpated 3.....  The Urban Wildlands Group,
                                                                                       Inc. 2005.
14. Deer Creek, Kyle Canyon.............       1950/1950  Presumed extirpated.......  Austin 1980.
15. Willow Creek........................       1928/1928  Presumed extirpated.......  Austin 1980; Weiss et al.
                                                                                       1997.
----------------------------------------------------------------------------------------------------------------
1 LVSSR = Las Vegas Ski & Snowboard Resort; LVSSR 2 is not identified as a separate site in Nevada
  Natural Heritage Program database (likely combined by Heritage with LVSSR 1).
2 Location is not mentioned in the petition.
3 Location is not identified in the Nevada Natural Heritage Program database.

    The Service presumes that the Mt. Charleston blue butterfly is 
extirpated from a location when it has not been sighted at that 
location through formal surveys or informal observation for more than 
twenty years. We presume the Mt. Charleston blue butterfly is 
extirpated from 6 of the 15 locations as noted in Table 1 (The Urban 
Wildlands Group, Inc. 2005, pp. 1-3; Service 2006b, pp. 8-9). The 
status of the Mt. Charleston blue butterfly at a location is described 
as presumed extant--ephemeral by the Service when the location is 
within the extant range of the subspecies and is within potential 
recruitment distance of an extant core colony. The butterfly exhibits 
metapopulation dynamics at these locations, likely emigrating to these 
smaller patches of habitat from the core colonies during years when 
environmental conditions are favorable (see subsequent core colonies, 
metapopulation dynamics, and favorable environmental conditions). At 
many of these ephemeral locations, the Mt. Charleston blue butterfly 
has not been sighted through formal surveys or informal observation 
since observed in 1995 by Weiss et al. (1997), or formal surveys have 
not occurred at that location since the butterfly was sighted in 1995 
by Weiss et al. (1997). As noted in Table 1, the current status of the 
Mt. Charleston blue butterfly is presumed extant--ephemeral at 6 of the 
15 locations or occurrences (The Urban Wildlands Group, Inc. 2005, pp. 
1-3; Service 2006b, pp. 7-8).
    Three of the 15 historical locations are presumed to be extant core 
colonies of the subspecies, as adults have been identified through time 
and were located during formal surveys in 1995 and 2005: South Loop 
Trail, Las Vegas Ski and Snowboard Resort (LVSSR) 1, and LVSSR 
2 (see Table 1) (Weiss et al. 1997; Boyd and Austin 2002; Boyd 
2005, p. 1; Service 2006b, p. 7; The Urban Wildlands Group, Inc. 2005, 
pp. 1-3; Service 2006b, p. 2). The term ``core colony'' as applied to 
our discussion of the Mt. Charleston blue butterfly is used only to 
describe a specific type of habitat for the butterfly. For our 
analysis, we define a Mt. Charleston blue butterfly core colony as a 
colony that meets the following factors: (1) Contains good quality 
habitat, defined as habitat containing high densities of the host 
plant, Torrey's milkvetch, with little grass cover, particularly 
nonnative grass cover (because grasses have been suggested as a reason 
for habitat degradation or successional changes that make habitat 
unsuitable for the subspecies, see discussion below); and (2) persists 
as habitat that maintains the metapopulation dynamics of the 
subspecies, such that adults are consistently sighted through formal or 
informal surveys within the colony and emigrants are provided to 
smaller, outlying habitat patches. The amount of habitat supporting two 
of the three core colonies of this subspecies has been mapped using a 
global positioning unit and field-verified by the Service and Forest 
Service; the core colony at LVSSR 1 occupies 2.4 acres (0.97 
hectares), and the core colony at LVSSR 2 occupies 1.3 acres 
(0.53 hectares),

[[Page 29936]]

totaling 3.7 acres (1.5 hectares) (Service 2006a, p. 1). The total area 
of the third core Mt. Charleston blue butterfly colony (South Loop 
Trail) has not been field-verified and is estimated at 5 acres (2 
hectares) within Kyle Canyon (The Urban Wildlands Group, Inc. 2005, p. 
2). Thus across its range, current estimates indicate the Mt. 
Charleston blue butterfly is restricted to less than 9 acres (3.6 
hectares) of core habitat, and the core habitat represents the only 
known occupied habitat remaining for this subspecies.
    Our files indicate that Boyd (2006, pp. 1-2) conducted focused 
surveys from late May through August of 2006 for the Mt. Charleston 
blue butterfly at all extant core colonies and at extant ephemeral 
locations. In addition to these locations, potential Mt. Charleston 
blue butterfly habitat along Griffith Peak, the South Loop Trail, North 
Loop Trail, Bristlecone Trail, and South Bonanza Trail was also 
surveyed in 2006. No observations of Mt. Charleston blue butterfly were 
made at any location, including the three core colonies (Boyd 2006, p. 
1). However, Murphy (2006, p. 1) hypothesizes that the butterfly 
potentially may have a survival mechanism to adapt and remain in 
diapause, and therefore may be able to survive unfavorable or inclement 
conditions for at least one season.
    Most butterfly populations occur in roughly the same numbers from 
year to year, though nearly every population experiences the occasional 
significant increase or decline depending on environmental conditions, 
and desert species seem particularly prone to dramatic fluctuations in 
numbers (Scott 1986, pp. 108-109). The Mt. Charleston blue butterfly 
has been characterized as particularly rare, but common in some years 
as noted in the petition (Boyd and Austin 1999, p. 17; The Urban 
Wildlands Group, Inc. 2005, p. 2). As previously mentioned, variations 
in precipitation and temperature that affect both the Mt. Charleston 
blue butterfly and its larval host plant are likely responsible for the 
fluctuation in population numbers between years (Weiss et al. 1997, pp. 
2-3 and 31-32). The specific requirements and timing of environmental 
conditions for larval host plant development, and in turn subspecies 
reproduction, is not known. Murphy et al. (1990, p. 43) note that in 
general, extreme weather (drought, late season snowstorms, unusually 
wet weather, etc.) often is the proximate cause of declines or 
extinctions of butterfly populations throughout the world. Drought has 
been shown to negatively impact other butterfly populations (Erlich et 
al. 1980, pp. 101-105; Thomas 1984, p. 344). Late season snowstorms 
have caused alpine butterfly population extinctions in Colorado 
(Ehrlich et al. 1972, p. 246), and high rainfall years have also been 
associated with population declines for other butterfly species in 
Europe (Dobkin et al. 1987, p. 164). Drought, late season snowstorms, 
unusually wet weather, and flash flooding associated with summer 
monsoon thunderstorms are extreme climatic phenomena that occur within 
the Spring Mountains at unpredictable intervals and have been reported 
as negatively affecting numerous butterfly species in the Spring 
Mountains, including the Mt. Charleston blue butterfly, in all stages 
of development and their host plants (Weiss et al. 1997, pp. 2-3 and 
31-32; Boyd et al. 2000, p. 3).
    The 1995 season was a boom year for the Mt. Charleston blue 
butterfly (Weiss et al. 1997, p. 32). Weiss et al. (1997, p. 32) 
commented that in 1995 almost every patch of host plants encountered 
during the flight season supported butterflies, including small 
isolated patches. The 1995 season probably represents the maximum 
population size when environmental conditions were most favorable and 
includes both the larger core colonies and the smaller, ephemeral 
habitat patches. In 1928 and 1963, the subspecies also exhibited higher 
abundances (Austin 1980, p. 22; The Urban Wildlands Group, Inc. 2005, 
p. 2).
    In contrast, the 1996 season represents a low population size for 
the Mt. Charleston blue butterfly when environmental conditions were 
unfavorable and very few patches of habitat were occupied. Weiss et al. 
(1997, pp. 32) indicate an extremely dry winter may have caused poor 
larval host plant quality and, thus, low overwintering success by Mt. 
Charleston blue larvae in 1996. In addition, Weiss et al. (1997, p. 32) 
suggested that heavy thunderstorms in early July 1996, which delivered 
3 inches of rainfall in a few hours, may have killed any Mt. Charleston 
blue butterflies that had emerged, as well as pupae waiting to emerge, 
leading to very reduced numbers observed in survey efforts that year.
    Similarly, there were no sightings of the Mt. Charleston blue 
butterfly in 2006 despite focused survey efforts. One possible 
explanation for the 2006 season may be extreme weather; prior to 2005, 
there were numerous years of drought, followed by a record snow in the 
winter of 2004-2005, a dry winter and spring in 2005-2006, and several 
localized, high rainfall events and cloudy conditions in the summer of 
2006. The following possible explanations for the lack of butterfly 
sightings were offered by two local Mt. Charleston blue butterfly 
experts as indicated in our files. Boyd (2006, p. 1) theorizes that the 
Mt. Charleston blue butterfly's host plant, Torrey's milkvetch, 
experienced delayed emergence in the year 2005 due to the persistence 
of the snow pack well into the plant's growing season. The delayed 
emergence of Torrey's milkvetch in 2005 could have negatively impacted 
butterfly reproduction in the year 2005, which would equate to low 
recruitment of emerging juveniles in the year 2006. Boyd (2006, p. 1) 
further hypothesized that since Torrey's milkvetch flowered in early 
May and June in 2006 (in response to a dry winter and spring), the 
emergence of the butterfly (typically in July) could have again been 
out of synchronization with the host plant. Murphy (2006, p. 1) 
proposed that the localized rain events in late June and July of 2006 
could have killed any butterflies that had emerged to date. Murphy 
(2006, p. 1) also suggests that the dry winter and spring may have 
prevented the Mt. Charleston blue butterfly from emerging at all. 
Murphy (2006, p. 1) hypothesizes that the butterfly potentially may 
have a survival mechanism to adapt and remain in diapause, and 
therefore may be able to survive unfavorable or inclement conditions 
for at least one season. Although individuals were not identified 
during surveys in 2006, we do not consider this subspecies extirpated 
from the three core colonies. It will be critical for the Mt. 
Charleston blue butterfly to successfully reproduce and pupae to emerge 
in 2007.
    Based on information in our files, most butterflies almost 
invariably exist as regional metapopulations (Murphy et al. 1990, p. 
44). Metapopulation dynamics make it difficult to interpret the true 
extent of the distribution of Mt. Charleston blue butterfly. Small 
habitats tend to support small populations that are frequently 
extirpated by events that are part of normal variation (Murphy et al. 
1990, p. 44). The continued existence of smaller populations requires 
the presence of one or more large reservoir populations or core 
colonies to provide emigrants to smaller, outlying habitat patches 
(Murphy et al. 1990, p. 44). Boyd and Austin (1999, p. 17) suggest 
smaller colonies of the Mt. Charleston blue butterfly may be ephemeral 
in the long term with the larger colonies of the subspecies being the 
only colonies to persist in poor, dry years.
    The Mt. Charleston blue butterfly's larval host plant, Torrey's 
milkvetch, is dependent on early successional habitat

[[Page 29937]]

(Weiss et al. 1995, p. 5). Healthy metapopulation dynamics allow 
butterflies, like the Mt. Charleston blue butterfly, to establish new 
colonies in new habitat patches as vegetation succession renders 
occupied habitat unsuitable (Hanski and Simberloff 1997, p. 9). Fire 
and avalanches are natural disturbances that help create this mosaic of 
different successional states that supports the Mt. Charleston blue 
butterfly (Weiss et al. 1995, p. 5). Forty-three percent (3.7 acres 
(1.5 hectares)) of remaining habitat known to be occupied by the 
butterfly occurs on the LVSSR, which operates on Forest Service lands 
under a special use permit. Weiss et al. (1995, p. 5) observed an old 
avalanche chute, which supports one of the three core colonies for this 
subspecies on a LVSSR ski run. Large-scale, natural avalanches in the 
LVSSR, which could have created new habitat for the butterfly, have 
been prevented for more than 40 years due to the regular use of 
explosives in the upper portions of the avalanche chutes by the LVSSR. 
Fire suppression and other Forest Service management practices have 
also limited the formation of new replacement habitat for the Mt. 
Charleston blue butterfly. Similar losses of suitable habitat in 
woodlands and their negative effect on butterfly populations have been 
documented elsewhere (Thomas 1984, pp. 337-338). However, as described 
in the petition, because the natural processes that create and maintain 
successional habitat in an early state, as required by Torrey's 
milkvetch, have been limited, the LVSSR now provides important core 
habitat for the Mt. Charleston blue butterfly (The Urban Wildlands 
Group, Inc. 2005, p. 2). Periodic maintenance (removal of trees and 
shrubs) of the ski runs has effectively arrested succession on the ski 
slopes and maintains the early successional state favorable to the Mt. 
Charleston blue butterfly; however, the ski runs are not specifically 
managed to benefit habitat for this subspecies and operation activities 
regularly modify and remove butterfly habitat.

Threats Analysis

    Section 4 of the Act and its implementing regulations (50 CFR 424) 
set forth the procedures for adding species to the Federal List of 
Endangered and Threatened Wildlife and Plants. A species may be 
determined to be an endangered or threatened species due to one or more 
of the five factors described in section 4(a)(1) of the Act: (A) 
Present or threatened destruction, modification, or curtailment of 
habitat or range; (B) overutilization for commercial, recreational, 
scientific, or educational purposes; (C) disease or predation; (D) 
inadequacy of existing regulatory mechanisms; or (E) other natural or 
manmade factors affecting its continued existence. In making this 
finding, we evaluated whether threats to the Mt. Charleston blue 
butterfly presented in the petition may pose a concern with respect to 
its survival. The Act identifies the five factors to be considered, 
either singly or in combination, to determine whether a species may be 
threatened or endangered. Our evaluation of these threats, based on 
information provided in the petition, is presented below.

A. Present or Threatened Destruction, Modification, or Curtailment of 
the Species' Habitat or Range

    The petitioner claims that present or threatened destruction, 
modification, or curtailment of the habitat or range of the Mt. 
Charleston blue butterfly threatens this subspecies such that listing 
may be warranted. The claim is detailed in the petition by multiple 
instances of destruction or modification of the subspecies' habitat by 
construction and other activities, including: (1) Bisection of habitat 
by South Loop Trail and unsanctioned trails created in habitat in Kyle 
Canyon; (2) resort improvements at LVSSR 1 in Lee Canyon; (3) 
construction of a berm at LVSSR 2 in Lee Canyon; (4) 
installation and expansion of snowmaking apparatus at LVSSR 2 
in Lee Canyon; (5) small construction activities at Foxtail Camp in Lee 
Canyon; (6) expansion of the water system at the Youth Camp in Lee 
Canyon; and (7) expansion of the parking lot at LVSSR in Lee Canyon 
(The Urban Wildlands Group, Inc. 2005, pp. 2-3). As further detailed 
below, information in our files supports the petitioner's claim and the 
examples cited.
    (1) The petition describes that Mt. Charleston blue butterfly 
habitat along South Loop Trail in Kyle Canyon (one of three core 
colonies) is being impacted by recreation activity, specifically 
unsanctioned hiking trails. Based on information in our files, an 
assessment of an unsanctioned hiking trail to a plane crash site in the 
vicinity of butterfly habitat identified that the unsanctioned trail 
has disturbed (through loss and trampling) habitat for the Mt. 
Charleston blue butterfly as stated in the petition (Service 2006c, pp. 
2-7).
    (2) The petition describes replacement of a snowmaking apparatus or 
line that occurred within and impacted the habitat at LVSSR 1, 
another of the three core colonies of the Mt. Charleston blue 
butterfly. This claim is supported by information in our files (The 
Urban Wildlands Group, Inc. 2005, p. 3; Service 2006a, pp. 1-5; Forest 
Service 2004a, p. 1-3; Forest Service 2004b, p. 9; Forest Service 
2006b, pp. 1-9). Based on the best available information in our files 
(habitat mapping performed by Weiss et al. (1995, Figure 8C) and 
habitat mapping performed by the Service and Forest Service in July 
2006 (Service 2006a, pp. 1-5)), we calculate that 2.4 acres (0.97 
hectares) of this core colony of Mt. Charleston blue butterfly habitat 
remains, and we estimate that the construction project associated with 
the replacement of the specified snowmaking line caused the loss of 0.2 
acres (0.08 hectares) of the core habitat.
    (3) The petition states that the construction of an avalanche 
deflection berm in 2000 or 2001 at the top of the northwestern-most ski 
run (location of the third core colony at LVSSR 2) caused loss 
and degradation of core butterfly habitat. The location of the earthen 
berm, and information in our files that maps the Mt. Charleston blue 
butterfly habitat on the LVSSR ski runs, verifies this assertion 
(Service 2006a, pp. 1-5).
    (4) The petition describes further impacts to the core colony 
habitat at LVSSR 2 associated with the replacement of a 
snowmaking apparatus or line in 2005 on a ski run east of the core 
colony, and information in our files confirms this construction project 
(Forest Service 2004c, p. 8). The petition claims that lower quality 
peripheral habitat for the butterfly was disturbed. Based on 
information in our files regarding the extent of the disturbance 
associated with the snowmaking line and other improvements in 2005, as 
well as the mapping of Mt. Charleston blue butterfly habitat at LVSSR 
2, the petition's assertion is accurate (Forest Service 2006b, 
pp. 1-9; Service 2006a, pp. 1-5). Outside of the core colony habitat at 
LVSSR 2, peripheral habitat of lower quality for the 
subspecies was impacted by the improvements.
    (5) The petition does not present specific information regarding 
the extent of impact from small construction projects at Foxtail Camp 
in Lee Canyon. We do not have any information in our files to 
corroborate or refute the petition's claim regarding impacts to Mt. 
Charleston blue butterfly habitat at this location.
    (6) The petitioner also claims that the expansion of the water 
system at the Youth Camp in Lee Canyon impacted habitat for the Mt. 
Charleston blue butterfly. This assertion is confirmed by a Forest 
Service report in our files (Forest Service 2002, pp. 16-18).

[[Page 29938]]

    (7) The petition identifies a location on the LVSSR where Mt. 
Charleston blue butterfly habitat was lost due to modifications to a 
parking lot near the end of State Route 156 (The Urban Wildlands Group, 
Inc. 2005, p. 3). Based on data in our files, the Mt. Charleston blue 
butterfly was first recorded at this location during 1995 surveys 
(Weiss et al. 1997, p. 10), and the subspecies has not been observed in 
the area in recent years (Boyd 2005, p. 1). The petition states that 
approximately 2 acres (0.81 hectares) once supported a large number of 
host plants for the butterfly at this site (The Urban Wildlands Group, 
Inc. 2005, p. 3). The modifications likely occurred in 2004, when the 
parking area was used as a temporary storage pond for snowmaking water. 
Given our knowledge of the habitat requirements for the butterfly and 
remaining host plants around the margins of the parking area, the 
petition accurately states that Mt. Charleston blue butterfly habitat 
was impacted by these modifications.
    Present destruction, modification, or curtailment of this 
subspecies' habitat or range is documented by numerous activities 
described in the petition and verified by information in our files. Of 
the seven claims made in the petition regarding habitat loss or 
modification, six were supported by information in our files: (1) 
Bisection of habitat by South Loop Trail and unsanctioned trails 
created in habitat in Kyle Canyon; (2) improvements at LVSSR 1 
in Lee Canyon; (3) construction of a berm at LVSSR 2 in Lee 
Canyon; (4) installation and expansion of snowmaking apparatus at LVSSR 
2 in Lee Canyon; (5) expansion of the water system at the 
Youth Camp in Lee Canyon; and (6) expansion of the parking lot at LVSSR 
in Lee Canyon. The petition states that the current situation of the 
Mt. Charleston blue butterfly is perilous, with the extant colonies all 
at risk of extinction (The Urban Wildlands Group, Inc. 2005, p. 2). 
Based on the information in the petition and our files, 15 locations 
have been occupied by the Mt. Charleston blue butterfly since 1928. The 
subspecies is presumed extirpated from 6 of the 15 locations. At 
another 6 locations, the butterfly's occurrence is extant, but 
ephemeral. The butterfly exhibits metapopulation dynamics at these 
locations, likely emigrating to these smaller patches of habitat from 
the core colonies during years when environmental conditions are 
favorable. The Mt. Charleston blue butterfly has not been sighted at 
the majority of these 6 extant ephemeral locations since 1995. Finally, 
3 of the 15 locations (estimated to encompass less than 9 acres (3.6 
hectares) of habitat) are currently known to be extant core colonies. 
Habitat loss and modification threatens all three of these occupied 
core colonies, as documented by the petition and verified by 
information in our files. We conclude that the petition presents 
substantial information to indicate that listing may be warranted due 
to the present or threatened destruction or modification of habitat or 
range for the Mt. Charleston blue butterfly.

B. Overutilization for Commercial, Recreational, Scientific or 
Educational Purposes

    Neither the petition nor information in our files provides any 
information pertaining to Factor B with regard to the Mt. Charleston 
blue butterfly.

C. Disease or Predation

    Neither the petition nor information in our files provides any 
information pertaining to Factor C with regard to the Mt. Charleston 
blue butterfly.

D. Inadequacy of Existing Regulatory Mechanisms

    Although the Mt. Charleston blue butterfly is not federally listed, 
some protections are in place, as documented in the petition. The 
subspecies is included in a 1998 Conservation Agreement for the Spring 
Mountains National Recreation Area, Clark and Nye Counties, Nevada 
(Conservation Agreement) signed by the State of Nevada, Forest Service, 
and the Service (Forest Service 1998, pp. 1-50). The Conservation 
Agreement described conservation actions for the butterfly on lands 
within the Forest Service's jurisdiction. In 2000, the 55 species that 
are the subject of the Conservation Agreement, including the Mt. 
Charleston blue butterfly, were incorporated as covered species under 
the Clark County Multiple Species Habitat Conservation Plan (Clark 
County MSHCP).
    The petition makes three assertions that inadequacy of existing 
regulatory mechanisms is a threat to the Mt. Charleston blue butterfly: 
(1) Responsibilities as described by section 5.6 of the Conservation 
Agreement have not been met; (2) required butterfly surveys were not 
conducted for a project at the LVSSR in 2005; and (3) no mitigation for 
the loss of habitat from projects described in the petition has 
occurred to meet the measurable biological goals of no net unmitigated 
loss under the Clark County MSHCP (The Urban Wildlands Group, Inc. 
2005, pp. 1-3). The following details these assertions.
    (1) The petition alleges that responsibilities as described in 
section 5.6 of the Conservation Agreement have not been met (The Urban 
Wildlands Group, Inc. 2005, p. 1). This section states that the Forest 
Service and other Conservation Agreement signatories will ``Work with 
Las Vegas Ski and Snowboard Resort to develop protective strategies for 
sensitive ecological resources. This will include investigating options 
for erosion control of the Lee Canyon ski slopes with native seed 
mixes, including Astragalus calycosus var. mancus to enhance butterfly 
habitat, management of herbicides and pesticides, and a plan for 
eventual elimination of nonnative seeding, and management of the Three 
Springs area'' (The Urban Wildlands Group, Inc. 2005, p. 1; Forest 
Service 1998, p. 39). With a change in ownership of the LVSSR in 2004, 
nonnative seeding at the LVSSR was eliminated. In addition, a Forest 
Service decision notice dated September 13, 2004, directed the LVSSR to 
prepare a monitoring plan for disturbed areas, which evolved into a 
broader Adaptive Management Vegetation Plan (Vegetation Plan) and a 
specific 2005 Program of Work (Forest Service 2004a, p. 2; Forest 
Service 2005a, pp. 1-24; Forest Service 2005b, pp. 1-11). One purpose 
of this Vegetation Plan was to implement the conservation actions 
described in section 5.6, as well as Forest Service General Management 
Plan objectives to benefit numerous endemic species within the LVSSR. 
The Vegetation Plan will guide revegetation efforts at the LVSSR from 
2005 through 2011. The objectives of this Vegetation Plan include: 
increase self-sustaining populations of sensitive plants species and 
butterfly host plants; eliminate the use and occurrence of nonnative 
species in the ski area; describe inventory guidelines and protocols; 
describe rehabilitation guidelines and protocols; describe monitoring 
guidelines and protocols; and facilitate maintenance, construction, and 
reconstruction, as well as limited expansion, of skiing opportunities 
and facilities (Forest Service 2005a, p. 3). Monitoring of disturbed 
areas and control plots, and targeted native seed collection, occurred 
in 2005 and 2006. On-the-ground cultivation or planting of native seed 
has not yet occurred. If implementation of the Vegetation Plan 
continues with success, the Service estimates that habitat restoration 
for the Conservation Agreement's species, including the Mt. Charleston 
blue butterfly, will be

[[Page 29939]]

realized in 3 to 5 years (1 to 3 more years for seed collection and 
cultivation, and 2 additional years for establishment of habitat). This 
Vegetation Plan is an important step towards meeting the objectives of 
section 5.6 of the Conservation Agreement, however, the Vegetation Plan 
was initiated in 2005 and its success is yet to be determined. Thus 
based on information in our files, the petition is correct that some 
responsibilities described in section 5.6 of the Conservation Agreement 
have not been initiated or completed, such as management of the Three 
Springs area, and on-the-ground cultivation or planting of native seed 
for erosion control and enhancement of butterfly habitat. However, the 
petition is incorrect with regard to other responsibilities under 
Section 5.6 of the Conservation Agreement, as some have been fulfilled 
or have been initiated, such as elimination of nonnative seeding, and 
development of the Vegetation Plan to move toward establishing native 
seed and butterfly host plants at the LVSSR.
    (2) The petitioner alleges that butterfly surveys were not 
completed for a project implemented in 2005 that disturbed Mt. 
Charleston blue butterfly habitat at the LVSSR (The Urban Wildlands 
Group, Inc. 2005, p. 3). Section 1.0 of the Conservation Agreement 
states that the Forest Service, as a general commitment, would 
``conduct pre-activity surveys for species of concern prior to taking 
an action'' (Forest Service 1998, p. 29). Information in our files 
confirms that pre-activity surveys for butterflies were not completed 
before either a 2005 construction project associated with replacing a 
snowmaking line that affected the core colony at LVSSR 1, or 
other LVSSR projects implemented in 2005 (Forest Service 2004c, p. 1; 
Forest Service 2005c, p. 7).
    (3) The petitioner also asserts that no mitigation for the loss of 
habitat from projects described in the petition has occurred to provide 
for no net unmitigated loss under the Clark County MSHCP (The Urban 
Wildlands Group, Inc. 2005, p. 3). As a signatory to the Implementing 
Agreement of the Clark County MSHCP, the Forest Service committed to 
implementing mitigation, minimization, and monitoring actions under the 
Clark County MSHCP for covered species on Forest Service lands in Clark 
County. The Clark County MSHCP Environmental Impact Statement 
identifies two measurable biological goals for the Mt. Charleston blue 
butterfly: (a) ``No net unmitigated loss of larval host plant or nectar 
plant species habitat in the Spring Mountains Natural Recreation 
Area,'' and (b) ``Maintain stable or increasing population numbers and 
host and larval plant species'' (RECON 2000a, Table 2.5, pp. 2-154).
    Information in our files confirms the petitioner's claim that 
mitigation did not occur for several projects noted in the petition, 
including: (a) The expansion of the water system at the Youth Camp in 
Lee Canyon, (b) the modification of the parking area at the LVSSR 
(likely in 2004), and (c) the construction of an avalanche deflection 
berm located at the top of the northwestern-most ski run at the LVSSR 
within the LVSSR 2 core colony for the Mt. Charleston blue 
butterfly in 2000 or 2001 (Forest Service 2002, pp. 15-18).
    However, with regard to the projects implemented in 2005, there is 
information in our files that the Forest Service based their permitting 
approval for these projects on implementation of the Vegetation Plan 
(Forest Service 2005a, pp. 1-24). One purpose of the Vegetation Plan is 
to achieve mitigation for loss of habitat from various LVSSR project 
impacts to affected Conservation Agreement species, including the Mt. 
Charleston blue butterfly. As stated above, the Vegetation Plan was 
initiated in 2005 with monitoring of disturbed areas and control plots, 
as well as targeted native seed collection, in 2005 and 2006. The 
Forest Service and the LVSSR made the commitment to provide for habitat 
restoration for projects that were implemented in 2005; however, on-
the-ground cultivation or planting of native seed has not yet occurred 
to replace the lost Mt. Charleston blue butterfly habitat. As 
previously stated, if implementation of the Vegetation Plan continues 
with success, the Service estimates that habitat restoration for the 
Mt. Charleston blue butterfly will be realized in 3 to 5 years (1 to 3 
more years for seed collection and cultivation, and 2 additional years 
for establishment of habitat). Overall, it appears that there has been 
a current net loss of Mt. Charleston blue butterfly larval host plant 
or nectar plant species habitat in the Spring Mountains National 
Recreation Area as a result of specific projects. With successful 
implementation of the Vegetation Plan, measurable biological goals of 
the MSHCP may be met within 5 years.
    In summary, the petition states the following three points: (1) 
Responsibilities have not been met under section 5.6 of the 
Conservation Agreement; (2) pre-activity butterfly surveys were not 
conducted for a project implemented in 2005; and (3) no mitigation for 
the loss of habitat from projects described in the petition has 
occurred. As described previously, certain responsibilities have been 
initiated or met under section 5.6 of the Conservation Agreement, 
although others have not yet been initiated or fully implemented. Pre-
activity butterfly surveys were not conducted prior to multiple 
construction projects at the LVSSR in 2005, as described in the 
petition and verified by information in our files. Mitigation for site-
specific impacts to butterfly habitat have been implemented for some 
projects, and not implemented for others. Now it appears that there has 
been a net loss of habitat containing Mt. Charleston blue butterfly 
larval host plant or nectar plant species in the Spring Mountains 
Natural Recreation Area as a result of implementation of specific 
projects; however, due to actions recently initiated, habitat 
restoration should be realized in the future. Despite these recent 
restoration efforts, the interim loss may still be substantial due to 
restricted size of the occupied habitat and the uncertain population 
status of the subspecies.
    Although there are existing agreements that intended to conserve 
the Mt. Charleston blue butterfly, to date these agreements either have 
not been implemented or the limited implementation does not appear to 
have provided sufficient conservation for this subspecies. Given the 
uncertain population status of and 2006 survey results for the Mt. 
Charleston blue butterfly, it is necessary for the Service to re-
evaluate the mechanisms currently in place to protect this subspecies. 
Based on the above information, we find that the petition presents 
substantial information to indicate that listing may be warranted due 
to the inadequacy of existing regulatory mechanisms to protect the Mt. 
Charleston blue butterfly.

E. Other Natural or Manmade Factors Affecting Its Continued Existence

    The petitioner describes the threat to Mt. Charleston blue 
butterfly habitat resulting from vegetation succession and introduced 
plant species (The Urban Wildlands Group, Inc. 2005, p. 2). The 
petition provides two illustrations of this threat: (1) The loss of 
habitat near Old Town in Kyle Canyon due to shading of the larval host 
plant (as a result of vegetative succession) and introduction of 
nonnative species including alfalfa; and (2) the loss of the butterfly 
from Lee Meadow in Lee Canyon (The Urban Wildlands Group, Inc. 2005, p. 
3). Based on information in our files, Weiss et al. (1995, p. 5) 
concluded host plant

[[Page 29940]]

densities in Lee Meadow appeared insufficient to support the Mt. 
Charleston blue butterfly. Decreases in the quality or abundance of 
larval host plant and nectar sources can be caused by changes in plant 
community composition, particularly changes associated with succession, 
disturbance, and grazing regimes (Murphy et al. 1990, p. 43). Changes 
in vegetation structure and composition associated with succession may 
have contributed to the loss of Torrey's milkvetch, and, therefore, to 
the loss of the Mt. Charleston blue butterfly at historic sites in Kyle 
Canyon (Boyd and Austin 2002, p. 13). Based on information in our 
files, Weiss et al. (1997, p. 33) describe the impact of erosion 
control plantings of grasses and alfalfa (Medicago sativa) on the 
butterfly's host plants at the LVSSR as a butterfly management issue 
due to competition with butterfly host plants and potential structural 
changes to butterfly habitat. Further information in our files 
confirmed that the LVSSR ski runs were seeded with both cultivated 
varieties of native and nonnative grasses and introduced forbs in the 
1970s and 1980s (Titus and Landau 2003, pp. 1-3).
    The petitioner also mentions wild horse grazing as an issue and 
notes that wild horses are nearly always present at one of the core 
colonies of the butterfly (LVSSR 1) (The Urban Wildlands 
Group, Inc. 2005, p. 2). The petition does not provide any supporting 
documentation to describe this threat or the extent of impact from the 
threat to the Mt. Charleston blue butterfly. Based on information in 
our files, the Clark County MSHCP identified trampling by wild horses 
and livestock grazing as potential threats to the subspecies and other 
butterflies (RECON 2000b, p. B-158). The extent of any impact from 
trampling and grazing to the Mt. Charleston blue butterfly and its host 
plants is undocumented or unknown.
    There is insufficient information in the petition or our files to 
adequately characterize the threat of vegetation succession, nonnative 
plant species, or wild horses at the locations identified in the 
petition or across the range of the subspecies. Therefore, we conclude 
that there is not substantial scientific or commercial information to 
indicate that listing the Mt. Charleston blue butterfly may be 
warranted due to the other natural or manmade factors described in the 
petition.

Finding

    We have reviewed and evaluated the five listing factors with regard 
to the Mt. Charleston blue butterfly, based on the information in the 
petition and in our files. On the basis of this review and evaluation, 
we find that the petition does present substantial information to 
indicate that listing the Mt. Charleston blue butterfly as threatened 
or endangered may be warranted.
    The Mt. Charleston blue butterfly is known only from the high 
elevations of the Spring Mountains in Clark County Nevada, where it 
depends upon its larval host plant, Torrey's milkvetch. The range of 
the Mt. Charleston blue butterfly is centered on the east side of the 
Spring Mountains in Kyle and Lee Canyons, on lands managed by the 
Forest Service in the Spring Mountains National Recreation Area of the 
Humboldt-Toiyabe National Forest. Based on historic records and 
surveys, the subspecies has occupied 15 locations since 1928. 
Currently, the Mt. Charleston blue butterfly is known to occupy three 
core colonies in Kyle and Lee Canyons. Two of the core colonies of the 
subspecies in Lee Canyon total 3.7 acres (1.5 hectares), while the size 
of the core colony in Kyle Canyon is estimated at 5 acres (2 hectares); 
thus, the Mt. Charleston blue butterfly is currently known to occupy 
less than 9 acres (3.6 hectares) of habitat.
    There is substantial information presented in the petition and 
verified by information in our files that listing may be warranted for 
the Mt. Charleston blue butterfly due to the present destruction, 
modification, or curtailment of the subspecies' habitat or range 
(Factor A) and the inadequacy of existing regulatory mechanisms (Factor 
D). Present habitat destruction and modification to the Mt. Charleston 
blue butterfly and Torrey's milkvetch was documented at the LVSSR in 
Lee Canyon from multiple projects implemented since 2000, including 
construction of a berm within a core colony, modifications to a parking 
lot, and replacement of snowmaking lines (one of which affected a core 
colony). In addition, expansion of the water system at the Youth Camp 
in Lee Canyon affected the butterfly's habitat. Finally, a core colony 
in Kyle Canyon is bisected by the South Loop Trail and is affected by 
an additional unsanctioned trail.
    The petition states that the current situation of the Mt. 
Charleston blue butterfly is perilous with the extant colonies all at 
risk of extinction (The Urban Wildlands Group, Inc. 2005, p. 2). Based 
on the information in the petition and our files, 15 locations have 
been occupied by the Mt. Charleston blue butterfly since 1928. The 
subspecies is presumed extirpated from 6 of the 15 locations. At 
another 6 locations, the butterfly's occurrence is extant, but 
ephemeral. The butterfly exhibits metapopulation dynamics at these 
locations, likely emigrating to these smaller patches of habitat from 
the core colonies during years when environmental conditions are 
favorable. The Mt. Charleston blue butterfly has not been sighted at 
the majority of these 6 extant ephemeral locations since 1995. As 
described in the petition and verified by information in our files, the 
butterfly's persistently occupied range is currently known to be 
restricted to three locations or colonies on approximately 9 acres (3.6 
hectares), and all three locations are threatened by habitat loss and 
modification. We are further concerned that formal surveys in 2006 were 
unable to identify any adult butterflies across the subspecies' known 
range, including at the three core colonies. While we do not consider 
the species extirpated from the three core colonies, successful 
reproduction and emergence of pupae in 2007 is critical for this 
subspecies.
    There is substantial information presented in the petition and 
verified by information in our files that listing may be warranted for 
the Mt. Charleston blue butterfly due to the inadequacy of existing 
regulatory mechanisms (Factor D). The petition describes and 
information in our files verifies that some responsibilities under the 
Conservation Agreement (Sections 1.0 and 5.6) have not been met. 
However, some responsibilities under the Conservation Agreement, such 
as elimination of non-native seeding at the LVSSR, have been met and 
still others have recently been initiated. Furthermore, the petition 
describes and information in our files verifies that mitigation for 
site-specific impacts to butterfly habitat have been implemented for 
some projects, and not implemented for others. It appears that 
currently there has been a net loss of habitat containing Mt. 
Charleston blue butterfly larval host plant or nectar plant species in 
the Spring Mountains National Recreation Area as a result of 
implementation of specific projects. Due to actions recently initiated, 
however, habitat restoration should be realized in the future. Although 
there are existing agreements in place that intended to conserve the 
Mt. Charleston blue butterfly, to date these agreements either have not 
been implemented or the limited implementation does not appear to have 
provided sufficient conservation for this subspecies. Given the 
uncertain population status of and the 2006 survey results for the Mt. 
Charleston blue butterfly, it is necessary for the Service to re-
evaluate the mechanisms currently in place to protect this subspecies.

[[Page 29941]]

    In summary, based on listing factors A and D, we conclude that the 
petition has presented substantial information that listing may be 
warranted for the Mt. Charleston blue butterfly. We will initiate a 
status review to determine whether listing the subspecies as threatened 
or endangered is warranted.

References Cited

    A complete list of all references cited herein is available, upon 
request, from the Nevada Fish and Wildlife Office (see ADDRESSES).

Author

    The primary author of this notice is the Nevada Fish and Wildlife 
Office (see ADDRESSES).

Authority

    The authority for this action is the Endangered Species Act of 
1973, as amended (16 U.S.C. 1531 et seq.).

    Dated: May 15, 2007.
H. Dale Hall,
Director, U.S. Fish and Wildlife Service.
 [FR Doc. E7-10140 Filed 5-29-07; 8:45 am]
BILLING CODE 4310-55-P