Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List Thorne's Hairstreak Butterfly as Endangered, 9991-10003 [2011-4038]

Agencies

• Fish and Wildlife Service
• DEPARTMENT OF THE INTERIOR

[Federal Register Volume 76, Number 36 (Wednesday, February 23, 2011)]
[Proposed Rules]
[Pages 9991-10003]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 2011-4038]


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DEPARTMENT OF THE INTERIOR

Fish and Wildlife Service

50 CFR Part 17

[Docket No. FWS-R8-ES-2010-0016; MO 92210-0-0008-B2]


Endangered and Threatened Wildlife and Plants; 12-Month Finding 
on a Petition To List Thorne's Hairstreak Butterfly as Endangered

AGENCY: Fish and Wildlife Service, Interior.

ACTION: Notice of 12-month petition finding.

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SUMMARY: We, the U.S. Fish and Wildlife Service, announce a 12-month 
finding on a petition to list Thorne's hairstreak butterfly (Callophrys 
[Mitoura] gryneus thornei) as endangered under the Endangered Species 
Act of 1973, as amended (Act). After review of all available scientific 
and commercial information, we find that listing Thorne's hairstreak 
butterfly is not warranted at this time. However, we ask the public to 
submit to us any new information that becomes available concerning the 
threats to Thorne's hairstreak butterfly or its habitat at any time.

DATES: The finding announced in this document was made on February 23, 
2011.

ADDRESSES: This finding is available on the Internet at https://www.regulations.gov at Docket Number FWS-R8-ES-2010-0016. Supporting 
documentation we used in preparing this finding is available for public 
inspection, by appointment, during normal business hours at the 
Carlsbad Fish and Wildlife Office, U.S. Fish and Wildlife Service, 6010 
Hidden Valley Road, Suite 101, Carlsbad, CA 92011. Please submit any 
new information, materials, comments, or questions concerning this 
finding to the above street address.

FOR FURTHER INFORMATION CONTACT: Jim Bartel, Field Supervisor, Carlsbad 
Fish and Wildlife Office, U.S. Fish and Wildlife Service, 6010 Hidden 
Valley Road, Suite 101, Carlsbad, CA 92011; by telephone at 760-431-
9440; or by facsimile to 760-431-9624. Persons who use a 
telecommunications device for the deaf (TDD) may call the Federal 
Information Relay Service (FIRS) at 800-877-8339.

SUPPLEMENTARY INFORMATION: 

Background

    Section 4(b)(3)(B) of the Endangered Species Act of 1973, as 
amended (Act)

[[Page 9992]]

(16 U.S.C. 1531 et seq.) requires that, for any petition to revise the 
Federal Lists of Endangered and Threatened Wildlife and Plants that 
contains substantial scientific or commercial information that listing 
a species may be warranted, we make a finding within 12 months of the 
date of receipt of the petition. In this finding, we determine whether 
the petitioned action is: (a) Not warranted; (b) warranted; or (c) 
warranted, but immediate proposal of a regulation implementing the 
petitioned action is precluded by other pending proposals to determine 
whether species are endangered or threatened, and expeditious progress 
is being made to add or remove qualified species from the Federal Lists 
of Endangered and Threatened Wildlife and Plants. Section 4(b)(3)(C) of 
the Act requires that we treat a petition for which the requested 
action is found to be warranted but precluded as though resubmitted on 
the date of such finding, that is, requiring a subsequent finding to be 
made within 12 months. We must publish these 12-month findings in the 
Federal Register.

Previous Federal Actions

    On August 8, 2006, we published 90-day findings for both the 
Thorne's hairstreak and the Hermes copper butterflies in the Federal 
Register (71 FR 44980 and 71 FR 44966, respectively). The findings 
concluded that the petitions and information in our files did not 
present substantial scientific or commercial information indicating 
that listing Thorne's hairstreak butterfly or Hermes copper butterfly 
may be warranted. For a detailed history of Federal actions involving 
Thorne's hairstreak butterfly prior to the 2006 90-day finding, please 
see the August 8, 2006, Federal Register publication (71 FR 44980).
    On March 17, 2009, Center for Biological Diversity (CBD) and David 
Hogan filed a complaint for declaratory and injunctive relief 
challenging the Service's decision not to list Thorne's hairstreak 
butterfly and Hermes copper butterfly as endangered or threatened under 
the Act. In a settlement agreement dated October 23, 2009 (Case No. 09-
0533 S.D. Cal.), the Service agreed to submit a new 90-day petition 
finding for Thorne's hairstreak butterfly to the Federal Register by 
April 2, 2010. As part of the settlement agreement, we agreed to 
evaluate the October 25, 2004, petition filed by CBD and David Hogan, 
supporting information submitted with the petition, and information 
available in the Service's files, including information that has become 
available since the publication of the negative 90-day finding in the 
Federal Register on August 8, 2006. If the 90-day finding determined 
that listing may be warranted, we agreed to submit a 12-month finding 
for Thorne's hairstreak butterfly to the Federal Register by March 4, 
2011. On April 5, 2010, we published a 90-day finding that determined 
listing of Thorne's hairstreak butterfly as endangered may be warranted 
(75 FR 17062). This notice constitutes the 12-month finding on the 
petition to determine whether listing the Thorne's hairstreak butterfly 
as endangered is warranted.

Subspecies Information

    It is our intent to discuss only those topics directly relevant to 
the listing of Thorne's hairstreak butterfly under the Act in this 12-
month finding. For more information on the taxonomy, biology, and 
ecology of Thorne's hairstreak butterfly, please refer to the 90-day 
finding published in the Federal Register on April 5, 2010 (75 FR 
17062). That document is available on the Internet at https://www.fws.gov/Carlsbad and at https://www.regulations.gov (under docket 
number FWS-R8-ES-2010-0016).

Taxonomy and Nomenclature

    Thorne's hairstreak butterfly was first described as Mitoura 
thornei based on a specimen collected in 1972 near Otay Lake by Fred 
Thorne (Brown 1983, p. 246). Biologists questioned the classification 
of Thorne's hairstreak butterfly as a species. Shields (1984, p. 53) 
relegated it to a brown subspecies of the juniper hairstreak (species 
or subspecies name loki) as Mitoura loki thornei. Scott (1986, p. 374) 
also classified it as a subspecies, but under the name Callophrys 
gryneus thornei, in part because he did not consider any taxa in 
Mitoura as a genus distinct from Callophrys. The classification of 
Mitoura thornei was evaluated in 1999 by the Committee on Scientific 
Names of North American Butterflies (Committee). The Committee reached 
consensus based on publications and arguments presented, and accepted 
classification of Thorne's hairstreak butterfly as a subspecies of the 
species Callophrys gryneus (Burns et al. 2000, p. 9). Subsequently, the 
Committee prepared the second edition of the Checklist of English Names 
of North American Butterflies in which Thorne's hairstreak butterfly 
was classified as Callophrys gryneus thornei (Cassie et al. 2001, p. 
9). Van Buskirk (2004) reviewed Thorne's hairstreak butterfly 
classification for the Service; this review concurred with the 
Committee's decision to classify Thorne's hairstreak butterfly as 
Callophrys gryneus thornei.
    The classification of Thorne's hairstreak butterfly continues to be 
a focus of investigation. Recent work that includes mitochondrial DNA 
and allozyme analysis indicates that Thorne's hairstreak is closely 
related to juniper hairstreak (Shiraiwa 2010, p. 1; Pratt 2010, in 
press), as originally suggested by Shields (1984, p. 53). Pratt's 
(2010, in press, p. 9) work also appears to support classifying Mitoura 
as a genus or subgenus, which would classify Thorne's hairstreak 
butterfly as a subspecies of Mitoura loki (the juniper hairstreak). 
Thorne's hairstreak butterfly has always been classified as a separate 
entity at some level (species or subspecies), and therefore it is a 
listable entity under the Act. As described above, recent work 
indicates that it is best classified as a subspecies close to the 
juniper hairstreak. The monophyletic group Mitoura may warrant 
recognition as a separate genus in the future.
    In this 12-month finding, we follow the most recent recommendation 
from the North American Butterfly Association Names Committee (Cassie 
et al. 2001, p. 9) and treat Thorne's hairstreak butterfly as a 
subspecies named Callophrys gryneus thornei.

Habitat

    Thorne's hairstreak butterfly habitat is characterized by interior 
cypress woodland, also recently known as Callitropsis forbesii Woodland 
Alliance (Tecate cypress stands) (Sawyer et al. 2009, pp. 101-102) 
dominated by its host plant, Hesperocyparis forbesii (Tecate cypress). 
This habitat is found on Otay Mountain, intermixed with chaparral 
between approximately 800 feet (ft) (244 meters (m)) and 3,290 ft (1003 
m) in elevation (i.e., the mountain peak). Adult Thorne's hairstreak 
butterflies are known to feed on the nectar of Eriogonum fasciculatum 
(California buckwheat), Ceanothus tomentosus (Ramona lilac), and Lotus 
scoparius (deerweed) in the vicinity of stands of H. forbesii (Faulkner 
and Klein 2005, p. 33). A recent study indicates Asclepias fascicularis 
(narrowleaf milkweed) is also used as an adult nectar source throughout 
the subspecies' range (Lucas 2009, pers. comm.). It is likely that 
Thorne's hairstreak butterfly, like most butterflies, uses a variety of 
plant species as nectar sources, and frequency of use is primarily 
dependent on availability.
    Thorne's hairstreak butterfly deposits eggs and feeds exclusively 
on its larval host plant, Hesperocyparis forbesii, to complete its life 
cycle (Brown 1983, p. 252). Williams and Congedo (2008)

[[Page 9993]]

studied aspects of larval host plant use by Thorne's hairstreak 
butterfly. They recorded number of eggs per H. forbesii tree, placement 
of eggs within trees, location of feeding damage on trees, and larval 
food choice, comparing mature (cone-bearing) trees to immature trees 
(no cones) (Williams and Congedo 2008, pp. 6-13). No significant 
difference was found between use of young or recent shoots (appressed 
scale leaves and stems) from mature and immature trees (Williams and 
Congedo 2008, pp. 15-18). Williams and Congedo (2008, p. 14) also noted 
that Thorne's hairstreak butterflies occupied stands of trees not more 
than 5 years old, and that approximately 7 percent of new fire regrowth 
trees were producing cones. Williams and Congedo (2008, p. 19) 
concluded larvae could develop by feeding on tissue from immature or 
mature trees; thus the availability of host plants for egg deposition 
in an occupied area is not likely limiting. These results confirm the 
hypothesis drawn from adult presence in new post-fire growth that 
oviposition is not limited by host plant age, as discussed in the 2006 
and 2010 90-day findings (71 FR 44980 and 75 FR 17062, respectively). 
Therefore, the best available information indicates Thorne's hairstreak 
butterfly larvae can utilize any available life stage of H. forbesii to 
complete its life cycle.
    Nectar source abundance is also a key factor in determining 
Thorne's hairstreak butterfly habitat suitability. Van Reusel et al. 
(2006, pp. 201, 207) studied a related species of hairstreak butterfly 
and, using predictive models, found that host plant and nectar source 
were the primary factors predicting green hairstreak butterfly 
distribution. Nectar sources are critical to support courtship, mating, 
and oviposition behaviors of butterflies such as Thorne's hairstreak 
butterfly (Williams and Congedo 2008, p. 20).

Biology

    The 90-day finding (75 FR 17062; April 5, 2010) incorrectly 
characterized the flight seasons as described in Faulkner and Klein 
(1995). Thorne's hairstreak butterfly has two flight periods per year 
(bivoltine). The first adult emergence and abundance peak occurs in 
late February through March and possibly early April, depending on 
winter rainfall. A second adult abundance peak occurs in late May or 
early June, with a possible third in September if there are summer 
monsoon rains (Klein 2010a, p. 1).

Distribution and Population Status

    We evaluated available information on the current range, historical 
range, and population status of Thorne's hairstreak butterfly to 
develop the most current understanding of its distribution and status.
    Our knowledge of Thorne's hairstreak butterfly's range has greatly 
increased over the past 10 years. The known pre-2003 fire distribution 
of Thorne's hairstreak butterfly approximately encompassed the 
northeast quadrant of Otay Mountain, including locations just southwest 
of the peak and a lower-elevation location east of Otay Lakes (Klein 
2010a, p. 2). The 2003 Mine Fire (also called the Otay Fire) perimeter 
encompassed all habitats where butterflies had been observed; however, 
post-fire surveys revealed a cluster of locations occupied by Thorne's 
hairstreak butterflies in the southwest quadrant of Otay Mountain 
outside of the mapped fire perimeter (Klein 2010a, p. 11). The 2007 
Harris Fire perimeter encompassed the lower north and east slopes of 
Otay Mountain, affecting a large portion of cypress forest in the 
northwest quadrant near Otay Lakes. Post-2007 fire surveys on Otay 
Mountain conducted by Lucas in 2010 included all areas within the 
species' range on Otay Mountain except known historical locations at 
the easternmost edge of the species' range (Lucas 2010), thus we are 
uncertain about the current status of the species at this easternmost 
edge of the species range. Only one stand of trees (that was not a 
known historical location for Thorne's hairstreak butterflies) was 
surveyed in the eastern area; no butterflies were observed (Lucas 2010; 
Klein 2010a, pp. 2, 12). Lucas also recorded a new Thorne's hairstreak 
butterfly occurrence location in an area within the northwest quadrant 
of Otay Mountain in 2010, thus expanding the pre-2007 fire known range 
(Lucas 2010). The newly discovered northwestern Otay Mountain 
observation location is over 1.5 miles (mi) (2 kilometers (km)) from 
the nearest previous Thorne's hairstreak butterfly observation in the 
northeast quadrant (Lucas 2010; Klein 2010a, pp. 2, 12).
    Surveys by Lucas on Otay Mountain in 2010 revealed the presence of 
Thorne's hairstreak butterfly throughout the majority of Hesperocyparis 
forbesii that burned in the 2003 fire, the 2007 fire, and in areas 
burned by both fires (unpublished data 2010).
    Additionally, the known distribution of Thorne's hairstreak 
butterfly on Otay Mountain is greater than was known at the time of the 
2004 petition. Therefore, the persistence of the butterfly in 
previously burned areas and the increase in the known butterfly 
distribution indicate that Thorne's hairstreak butterfly has either 
successfully recolonized burned areas or persisted within mapped fire 
perimeters on Otay Mountain.
    A previously unknown Thorne's hairstreak butterfly observation was 
also documented in 2010 off of Otay Mountain at a lower elevation in 
approximately 1 ac (0.4 ha) of atypical, created habitat, which 
suggests that Thorne's hairstreak butterfly either has the ability to 
recolonize small Hesperocyparis forbesii stands at lower elevations or 
that this observation may represent a new occurrence that was not 
previously documented. Of note, this new location:
    (1) Is in the Otay River Valley, at the mouth of O'Neal Canyon 
(Busby 2010a, pp. 1-2; Cooper 2010a, p. 1) and is outside the known 
Thorne's hairstreak butterfly range;
    (2) Is over 2.5 mi (4 km) from, and over 1000 ft (305 m) lower in 
elevation than, the nearest occupied site upslope at the base of Otay 
Mountain (as described by Lucas 2010, slide 15; Google Earth imagery);
    (3) Is approximately 500 ft (152 m) lower in elevation than the 
lowest previously recorded observation east of Otay Lake (site 5 
described by Klein 2010a, p. 2); and
    (4) Occurs on land conserved and managed by the City of Chula 
Vista, which is the only known occupied area located entirely outside 
of the Bureau of Land Management (BLM) Otay Mountain Wilderness (Klein 
2010b, p. 1).
    The June 15 (Busby 2010a, pp. 1-2; Cooper 2010a, p. 1) and June 23, 
2010, (Anderson 2010, p. 1; Cooper 2010b, pp. 1-2) observations of 
adult butterflies at the Otay River Valley location are also the latest 
ever recorded for Thorne's hairstreak butterfly during a flight season 
(Klein 2010b, p. 1). This late record is likely the result of unusually 
cool spring weather in 2010, creating prolonged and cooler moist river 
valley microclimate conditions. A June 1996 satellite image does not 
show Hesperocyparis forbesii stands at this location (Google Earth 
historical imagery accessed 2010). Although we do not have 
documentation of how or why the H. forbesii was established at this 
location, analysis of historical satellite imagery from 1996 to 2010 
and observations of individuals familiar with the site lead us to 
believe the trees were planted as seedlings from a nursery to replace 
native vegetation removed when a gas utility pipeline was installed in 
1996 (Anderson 2010, p. 1;

[[Page 9994]]

Cooper 2010b, pp. 1-2; Busby 2010b, p. 1). Regardless, occupancy of 
this newly discovered site in created habitat supports the hypothesis 
that Thorne's hairstreak butterfly is opportunistic and relatively 
resilient (i.e., able to persist at a new, lower elevation level in 
more moist microhabitat conditions than previously known to occur).
    Results from a previous hairstreak butterfly movement study also 
support the hypothesis of natural colonization. Specifically, Robbins 
and Small (1981, p. 308) studied movement of hairstreak butterflies 
(Lycaenidae: Eumaeini) in Panama and reported:
    (1) Observations of 128 species (47 percent of the known Panamanian 
hairstreak butterfly fauna) blown across the landscape by winds with 
speeds of 10 to 25 miles per hour (mi/hr) (15 to 40 kilometers per hour 
(km/hr));
    (2) More than 80 percent of these species were blown through 
habitats where they are not normally found;
    (3) Some species normally found in high-elevation habitats were 
observed 3 mi (5 km) from the nearest upland habitat; and
    (4) Seventy percent of the observed specimens were females (whereas 
typical sex ratios for hairstreak butterfly populations have more males 
than females), and 74 percent of captured females (a subset of those 
observed) had been mated.
    Robbins and Small (1981, pp. 311-12) concluded hairstreak 
butterflies are likely to be dispersed by wind and can successfully 
colonize suitable downwind habitats. In southern California, annual 
Santa Ana winds often produce westerly winds of 25 to 37 mi/hr (40 to 
60 km/hr) from fall through spring (Westerling et al. 2004, p. 290), 
and likely disperse insects. We believe this type of wind-assisted 
dispersal occurs at Otay Mountain, and is a likely explanation of how 
Thorne's hairstreak butterfly became established in the Otay River 
Valley stand of Hesperocyparis forbesii.
    The 90-day finding (75 FR 17062; April 5, 2010) stated the current 
distribution of Hesperocyparis forbesii in the Otay Mountain area 
encompasses 454 ac (183 ha) post-2003 fire (Lucas 2009, unpublished 
data), and compared this to historical Otay Mountain records that 
indicate H. forbesii once covered approximately 7,500 ac (3,035 ha) 
(California Natural Diversity Database (CNDDB) GIS database 2003). 
After further evaluation of all available host plant distribution 
information, we determined the acreage values cannot be compared as 
described in the 90-day finding because the values are a result of 
different mapping methodologies. Data from 2007 revealed that H. 
forbesii on Otay Mountain encompasses approximately 7,556 ac (3,058 ha) 
(CNDDB GIS database 2007). Additionally, the San Diego Association of 
Governments (SANDAG) produced a vegetation map of Southern Interior 
Cypress Forest on Otay Mountain equal to 5,693 ac (2,304 ha) (SANDAG 
GIS database, 1995). The smallest and most recent H. forbesii 
distribution area estimate of 454 ac (183 ha) cited in the 90-day 
finding (75 FR 17062; April 5, 2010) reflects stand-scale mapping 
focused on groups of 20 or more trees greater than 3.3 ft (1 m) in 
height, with smaller stands included when encountered incidentally 
(Forister and Lucas 2009, p. 1).
    Comparison of the CNDDB and SANDAG vegetation databases also 
indicates differences in mapping methodology. The two vegetation-based 
mapping methods vary in the areas mapped as occupied by Hesperocyparis 
forbesii, with only approximately half the area mapped in 1995 (SANDAG 
GIS database, before the 2003 fire) overlapping occupied areas mapped 
in 2007 (CNDDB GIS database, after the 2003 fire). Field inspection of 
three H. forbesii stands along the Minewawa truck trail that were 
within the 2003 fire perimeter revealed new growth of immature cypress 
throughout (Anderson 2010, p. 1). One H. forbesii location did not 
correspond with any location mapped by Lucas (2010 unpublished data), 
while the other two corresponded with Lucas's mapped areas and observed 
Thorne's hairstreak butterfly observations (Lucas 2010, unpublished 
data). Furthermore, approximately one-third of mapped Thorne's 
hairstreak butterfly observation locations fall outside all three 
mapped H. forbesii distributions discussed above.
    Our current analysis of Thorne's hairstreak butterfly habitat 
distribution indicates most of the habitat is relatively protected. 
Approximately 88 percent of cypress woodland is within the BLM Otay 
Mountain Wilderness area, and 11 percent is within the planning area of 
the San Diego Subarea Plan under the San Diego MSCP (see Factor A 
discussion below). The remaining one percent is privately owned. 
Occupied habitat within the City of Chula Vista Subarea Plan planning 
area is approximately 1 ac (0.4 ha; see above discussion).
    To summarize, available vegetation mapping of cypress forest can 
approximate the Thorne's hairstreak butterfly population distribution, 
while Lucas' data map of cypress forest (which is on a stand (sub-
population)-scale) is not yet comprehensive and thus cannot approximate 
the Thorne's hairstreak butterfly population distribution. It is not 
clear if either scale of cypress mapping corresponds with Thorne's 
hairstreak butterfly habitat distribution at either a butterfly 
population distribution or sub-population level. As a result, we are 
unable to accurately estimate the change in distribution of Thorne's 
hairstreak butterfly habitat on Otay Mountain because of the differing 
mapping techniques and because Hesperocyparis forbesii stands are still 
recovering from the 2003 and 2007 fires.
    Finally, Geographic Information System (GIS) analysis of historical 
fire perimeters indicates the majority of Thorne's hairstreak butterfly 
habitat has burned only once or twice in the past 100 years (see Factor 
A discussion below). All available data indicate that because cypress 
forest regrows after fire, and Thorne's hairstreak butterflies 
recolonize cypress forest regardless of host plant age, the 
distribution of habitat has not changed significantly following the 
recent fires.
    While individual Thorne's hairstreak butterflies are likely lost 
when fire burns stands of Hesperocyparis forbesii (as discussed in the 
90-day finding (75 FR 17062; April 5, 2010)), more recent data 
(discussed above) support the hypothesis that Thorne's hairstreak 
butterfly populations are relatively resilient to fire. Discovery of 
occupied habitat in 2007 and 2010 within the 2003 and 2007 fire 
perimeters, and the newly colonized created habitat in 2010 in the Otay 
River Valley (see above discussion) indicates Thorne's hairstreak 
butterflies can move relatively considerable distances, readily 
colonize new stands of H. forbesii, and increase their numbers to 
detectable levels over a period of 5 to 10 years. The recently recorded 
Otay River Valley location represents a confirmed Thorne's hairstreak 
butterfly range expansion over the past 10 years. Furthermore, we have 
no evidence supporting a permanent range contraction or curtailment 
anywhere throughout the subspecies' known distribution.

Summary of Information Pertaining to the Five Factors

    Section 4 of the Act (16 U.S.C. 1533) and implementing regulations 
(50 CFR part 424) set forth procedures for adding species to, removing 
species from, or reclassifying species on the Federal Lists of 
Endangered and Threatened Wildlife and Plants. Under section 4(a)(1) of 
the Act, a species may be determined to be endangered or threatened 
based on any of the following five factors:

[[Page 9995]]

    (A) The present or threatened destruction, modification, or 
curtailment of its habitat or range;
    (B) Overutilization for commercial, recreational, scientific, or 
educational purposes;
    (C) Disease or predation;
    (D) The inadequacy of existing regulatory mechanisms; or
    (E) Other natural or manmade factors affecting its continued 
existence.
    In making this 12-month finding, information pertaining to Thorne's 
hairstreak butterfly in relation to the five factors provided in 
section 4(a)(1) of the Act is discussed below. In making our 12-month 
finding on the petition, we considered and evaluated the best available 
scientific and commercial information.
    In considering whether a species warrants listing under any of the 
five factors, we look beyond the species' exposure to a potential 
threat or aggregation of threats under any of the factors, and evaluate 
whether the species responds to those potential threats in a way that 
causes actual impact to the species. The identification of threats that 
might impact a species negatively is not sufficient to compel a finding 
that the species warrants listing. The information must include 
evidence indicating that the threats are operative and, either singly 
or in aggregation, affect the status of the species. Threats are 
significant if they drive, or contribute to, the risk of extinction of 
the species, such that the species warrants listing as endangered or 
threatened, as those terms are defined in the Act.

Factor A. The Present or Threatened Destruction, Modification, or 
Curtailment of Its Habitat or Range

    The following potential threats that may affect the habitat or 
range of Thorne's hairstreak butterfly, discussed in this section, 
include: (1) Wildfire, (2) climate change as it relates to wildfire 
(climate change is discussed further under Factor E below), (3) habitat 
fragmentation, and (4) road and firebreak construction required for 
national security and fire management (U.S. Customs and Border 
Protection) activities. We also discuss benefits to Thorne's hairstreak 
butterfly and its habitat in the Habitat Conservation Plans (HCPs) and 
Natural Community Conservation Plans (NCCPs) section below. In the 90-
day finding (75 FR 17062; April 5, 2010), we indicated that based on 
the petition, recreational traffic, prescribed burns, and grazing were 
potential threats to Thorne's hairstreak butterfly. In the development 
of this 12-month finding, we further investigated the possibility that 
these activities were potential threats and found no evidence that 
recreational traffic, prescribed burns, or grazing were occurring or 
affecting the species or its habitat. Therefore, we have determined 
that these factors are not threats to the subspecies (see discussions 
below under the Road and Firebreak Construction section, the Factor D 
discussion, and the Factor E discussion).
Wildfire and Climate Change Related to Wildfire
    Fire regimes are based on the temporal and spatial patterns of 
ignition sources, fuel, weather, and topography (Pyne et al. 1996, p. 
48). It is also important to understand that fire severity, or the 
ecological impact of a fire and recovery of an ecosystem (Keeley and 
Fotheringham 2003, p. 231), can be different from fire intensity, or 
the energy released per length of fire front (Borchart and Odion 1995, 
p. 92). Additionally, large fires are not always equivalent to high-
intensity fires (Keeley and Fotheringham 2003, p. 231). This is 
particularly important when assessing effects of fire on chaparral 
communities. Fire often burns in a mosaic pattern at different 
intensities, thereby resulting in differing levels of effects on 
particular species and habitats. Therefore, the inclusion of a specific 
mapped fire perimeter is not a reliable indicator of the level of 
mortality or habitat destruction.
    According to Keeley and Fotheringham (2003, pp. 242-243), the 
historical natural fire regimes in southern California were likely 
characterized by many small lightning-ignited fires in the summer, a 
few large fires in the fall, and a variable fire intensity. However, 
the fire frequency (number of fires in a given area, not necessarily 
overlapping) has increased in North American Mediterranean Shrublands 
in California since about the 1950s. Southern California has 
demonstrated the greatest increase in wildfire ignitions, primarily due 
to an increase in population density beginning in the 1960s, and thus 
accessibility to new areas (Keeley and Fotheringham 2003, p. 240).
    We analyzed the past 40 years of fire patterns at Otay Mountain and 
found that the spatial and temporal historical fire regime described by 
Keeley and Fotheringham (2003) is confirmed at this location as 
illustrated in Table 1.

  Table 1--Spatial and Temporal Historical Fire Regime and Fire Impact on Southern Interior Cypress Forest for
                                   Otay Mountain, San Diego County, California
----------------------------------------------------------------------------------------------------------------
                                                                                       Cypress        Cypress
                                                       Total fire                   forest within  forest within
                        Year                           perimeter       Number of         fire           fire
                                                        (acres)          fires        perimeter      perimeter
                                                                                       (acres)       (hectares)
----------------------------------------------------------------------------------------------------------------
1971...............................................          56.04               1          18.97           7.67
1976...............................................       1,656.05               1          28.68          11.6
1978...............................................         600.48               1          22.67           9.17
1979...............................................       7,557.45               3       1,062.83         430.11
1980...............................................       3,313.64               1          36.97          14.96
1981...............................................         371.67               1          60.5           24.48
1982...............................................       1,076.56               4         124.42          50.35
1983...............................................         666.87               2         106.91          43.26
1985...............................................         188.37               1          19.14           7.74
1986...............................................         965.5                1           0.34           0.13
1987...............................................          54.71               1           3.54           1.43
1989...............................................         129.8                1           0.06           0.02
1990...............................................          63.33               1           7.4            2.99
1993...............................................         641.76               1          24.24           9.81
1994...............................................       2,983.35               1         103.09          41.71
1995...............................................         156.37               2          14.73           5.96
1996...............................................      18,460.02               5       4,186.08       1,694.05

[[Page 9996]]

 
1999...............................................         118.48               1          11.14           4.51
2003...............................................      44,884.10               1       7,548.9        3,054.95
2005...............................................         359.15               2          37.94          15.35
2007...............................................      90,738.46               1       1,279.76         517.9
2008...............................................         124.75               2           0.67           0.27
----------------------------------------------------------------------------------------------------------------

    The concern for wildfire effects to Thorne's hairstreak butterfly 
is primarily associated with loss of Hesperocyparis forbesii trees 
prior to the production of seed cones, which can result in the 
extirpation of a given stand (see Habitat section above). 
Hesperocyparis forbesii is a small tree generally associated with 
``chaparral ecosystems in southern California and northern Baja 
California, Mexico'' (de Gouvenain and Ansary 2006, p. 447). Chaparral 
is considered a crown-fire ecosystem, meaning ecosystems which ``have 
endogenous mechanisms for recovery that include resprouting from basal 
burrs and long-lived seed banks that are stimulated to germinate by 
fire'' (Keane et al. 2008, p. 702). These ecosystems are also resilient 
to high-intensity burns (Keeley et al. 2008, p. 1545). Seed cones of 
western cypress (Hesperocyparis) mature in the second year, generally 
remain closed at maturity, and open after many years or in response to 
fire (Adams et al. 2009, p. 180). As a result, H. forbesii, like most 
western cypresses, has serotinous or closed-cones that allow the 
species to withstand fire.
    While Zedler (1977, p. 456) indicated that cone production for 
Hesperocyparis forbesii begins around 10 years of age, Dunn (1986, p. 
369) reported production ``begins at about 5-7 years of age, but is 
sporadic until the trees reach about 30 years in age.'' Dispersal and 
germination of seeds is predominantly a result of fire, which results 
in death of the parent plant (Zedler 1977, p. 456). However, Zedler 
(2010a, pp. 1-2) stated that ``H. forbesii does not require fire to 
germinate and establish seedlings, although the frequency with which 
germination without fire occurs in natural stands is low, and the 
survival of seedlings that do germinate is probably even lower.'' 
Moreover, given that H. forbesii is a long-lived (more than 100 years) 
tree (Markovchick-Nicholls 2007, p. 4), with some individual trees on 
Guatay Mountain estimated to exceed 150 years in age (Dunn 1986, p. 
369), the need for reproduction in the absence of fire is low.
    Hesperocyparis forbesii biology, status, and management needs were 
recently discussed at a workshop on June 16, 2010 (Burrascano 2010, pp. 
1-4). Some attendees indicated that the H. forbesii stands on Otay 
Mountain are declining over the long term and that increased fire 
frequency poses a threat to the tree (Burrascano 2010, pp. 1-4); 
however, this assumes a significant correlation between the increased 
fire frequency in southern California and a decrease in the burn return 
interval within any given occupied cypress stand. Regarding the 
likelihood of extirpation, Zedler (2010b, p. 2) stated that ``it is 
very unlikely this species will be [extirpated] in 100 years, almost 
zero chance in 50.'' Specifically, Zedler (2010b, p. 1) believes the 
statistical probability of H. forbesii being extirpated from Otay 
Mountain (assuming relative independence of stands) is very low or 
insignificant. Zedler (2010b, p. 1) also concluded that as the number 
of fires in any area of ground per time increases, the average area 
burned in any given fire decreases; hence, to extirpate H. forbesii 
completely would require almost a saturation of ignitions, which is 
also unlikely. This information supports the unlikely extirpation of H. 
forbesii in the foreseeable future.
    Regarding the likelihood of decline, Markovchick-Nicholls (2007, p. 
v) used available data and stochastic matrix population models to 
assess the current risk of decline of Hesperocyparis forbesii under a 
range of southern California fire regime scenarios, and to rank 
management options and research priorities. Her model results suggest 
that H. forbesii will decline under most fire regime scenarios over the 
long term, but that this trend may be difficult to detect in the short 
term (Markovchick-Nicholls 2007, p. 41). Model results indicated that 
fire breaks could be highly effective for H. forbesii conservation, if 
designed to minimize removal of H. forbesii (Markovchick-Nicholls 2007, 
p. 41). In contrast, collection of seed in older H. forbesii stands for 
distribution in reproductively immature stands poses much less risk to 
the species, but also has much less dramatic effects on the persistence 
of the species than fire breaks do, even if successful (Markovchick-
Nicholls 2007, p. 41). Current BLM policy (BLM 2010a, pp. 6-7) dictates 
any future firebreak and road construction projects in Thorne's 
hairstreak butterfly habitat on Otay Mountain minimize impacts to the 
butterfly (see also Factor D discussion below), while reducing the 
threat of fire to the subspecies and its host plant by slowing the 
spread of fire once ignited.
    To address the issue of fire and how it relates to Thorne's 
hairstreak butterfly habitat loss, we conducted several GIS-based 
analyses of past fire frequencies and burn patterns on Otay Mountain. 
As described in the 90-day finding (71 FR 44980; August 8, 2006), we 
used GIS data in our files to overlay Hesperocyparis forbesii 
distribution on the map provided in the petition illustrating multiple 
fires that have burned through and near Thorne's hairstreak butterfly 
locations over the past century, and determined the majority of H. 
forbesii was within one or two fire perimeters during the 93-year 
period from 1910 to 2003. Furthermore, as discussed above, the areas of 
overlap between the 2003 and 2007 fire perimeters were relegated to 
lower elevation areas where host plant density is lowest. This result 
corresponds with the most conservative fire regime scenario in the 
Markovchick-Nicholls models discussed above (46 years), which is the 
scenario where the population appeared the most stable (Markovchick-
Nicholls 2007, p. 41). The above information further supports the 
unlikely decline or extirpation of H. forbesii in the foreseeable 
future.
    Using the most recent estimate (based on 2010 data) of 7,549 ac 
(3,055 ha) (CNDDB GIS Database 2010) of cypress forest on Otay 
Mountain, we calculated the overlap for the three largest fires in the 
last 15 years (1996, 2003, and 2007).

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In 1996, 55 percent of cypress forest was within a mapped fire 
perimeter. In 2003, 100 percent of the cypress forest was within the 
mapped fire perimeter. In 2007, 17 percent of cypress forest was within 
the mapped fire perimeter. One hundred percent of the cypress forest 
within the 1996 fire perimeter was also within the 2003 fire perimeter, 
whereas only 17 percent of the area within the 2003 perimeter was also 
within the 2007 fire perimeter. Over the last 15 years, only 9 percent 
of cypress forest was within all three fire perimeters, and one 
approximately 97-ac (39-ha) stand near the peak within the mapped 2003 
fire perimeter is estimated to have not burned in approximately 40 
years (Allison 2011, p. 1). The 2007 Harris Fire perimeter encompassed 
the lower north and east slopes of Otay Mountain, overlapping with the 
2003 burn perimeter primarily around the base of the mountain, 
indicating the pattern observed by Dunn (1984, p. 90) has not changed 
significantly over the past 27 years (1983-2010). In 1986, Dunn (p. 
374) concluded most of the cypress on Otay Mountain were reaching full 
maturity and a fire would result in little damage to the population, 
because it would in fact result in maximum seed dispersal and 
recruitment.
    Despite multiple fires over the last four decades on and around 
Otay Mountain (see Table 1), our analysis confirms Dunn's conclusion 
that fire does not have a significant impact on the cypress forest on 
Otay Mountain (Dunn 1986, p. 374). A recent survey documented that not 
all Hesperocyparis forbesii individuals within mapped fire perimeters 
are burned (Anderson 2010, p. 1). Only 11 of 122 Thorne's hairstreak 
butterfly observation locations recorded in 2010 by Lucas (unpublished 
data 2010) and only 17 percent of the associated cypress forest fell 
within both the 2003 and 2007 mapped fire perimeters (Carlsbad Fish and 
Wildlife Office GIS database). Throughout the areas that burned again 
in 2007, cypress regrowth and Thorne's hairstreak butterflies were 
observed in 2010. Furthermore, recent border fence construction and 
other enforcement activities in the Otay Mountain Wilderness area have 
reduced foot traffic by illegal immigrants from Mexico (Ford 2010, p. 
1), reducing the likelihood of fire ignition resulting from this 
source.
    As described above, Santa Ana winds and human-caused ignitions are 
important factors in southern California's shrubland and forest fire 
regimes. Because the Santa Ana wind events in fall and winter are 
driven by large-scale patterns of atmospheric circulation, researchers 
have developed projections for Santa Ana Occurrence (SAO) using global 
climate models (GCM) (Miller and Schlegel, 2006, p. 1). Results 
obtained from one GCM do not show an increase in the total number of 
annual SAOs; however, they did find a temporal shift in SAOs, with a 
decrease during the months of September and October and an increase in 
December (Miller and Schlegel, 2006, p. 3). The effects of this shift, 
coupled with predicted decreased precipitation (see Climate Change 
section in Factor E discussion below) to fire regime are unclear; 
however, December and January are typically the wettest months on 
record in Southern California (National Oceanic and Atmospheric 
Administration 2005). This temporal shift of SAOs from a time following 
the driest period of the year (May to October) to after the fall and 
winter rains begin (Scripps Institute of Oceanography 2010) would 
likely reduce the potential for and impact of wind and human-caused 
ignitions in southern California.
    The output from climate change models predicts a 50-percent 
contraction in mixed evergreen woodland and shrubland vegetation 
(general vegetation types that may include Hesperocyparis forbesii 
stands) in California for the time period from 2070 to 2099 (Lenihan et 
al. 2003, p. 1674) (for recent information on future climate 
predictions, see Factor E discussion). Lenihan et al. (2003, p. 1674) 
found that the most prominent feature of the vegetation class's 
response to the drier model scenario was the advancement of grassland 
into the historical range of mixed evergreen woodland and shrubland. 
Such vegetation changes could reduce host plant and nectar source 
availability for Thorne's hairstreak butterfly, as woody vegetation 
declines and grasses replace native flowering forbs. Based on the above 
discussion, nectar source availability may be a determining factor in 
Thorne's hairstreak butterfly occupancy; however, the general climate 
change vegetation effect models (Lenihan et al. 2003, p. 1674) found 
the simulated response to changes in precipitation were complex, 
involving changes in tree-grass competition mediated by fire.
    We are unable to predict the changes in climate, especially on a 
localized, small scale such as Otay Mountain, as well as what the 
impacts to Thorne's hairstreak butterfly and its habitat may be because 
this area is small relative to the resolution of vegetation change 
prediction models (which used climate models of intermediate scale to 
predict vegetation responses) and contains a relatively unique 
community dominated by the rare endemic cypress (see also Factor E 
discussion). While uncertainty exists regarding the potential effects 
of climate change on wildfire and habitat loss, and despite the 
increasing frequency of fires in southern California, the best 
available information does not indicate the average burn return 
interval per given area of cypress forest is decreasing, and it does 
indicate ignition sources on Otay Mountain have been reduced compared 
to historical levels; therefore, wildfire has not been, and is not 
likely to be, a significant threat to the Thorne's hairstreak butterfly 
or its habitat now or in the foreseeable future.
Habitat Fragmentation
    We examined the possibility of habitat fragmentation affecting 
Thorne's hairstreak butterfly. The connectivity of habitat occupied by 
a butterfly population is not defined by host plant distribution at the 
scale of host plant stands or patches, but rather by adult butterfly 
movement that results in interbreeding (see Service 2003a, pp. 22, 162-
165). Any loss of resource contiguity on the ground that does not 
affect butterfly movement, such as burned vegetation or road 
construction through stands of cypress, may degrade habitat but does 
not fragment a population. Therefore, in order for butterfly habitat to 
be considered fragmented, movement must be prevented by a barrier, or 
the distance between remaining host plants where larvae develop must be 
greater than adult butterflies will move to mate or deposit eggs. If it 
occurred, habitat fragmentation might create smaller, more vulnerable 
populations (see Factor E discussion below); however, the best 
available information indicates that habitat fragmentation has not 
occurred on Otay Mountain (see Distribution and Population Status 
section above). Hesperocyparis forbesii has demonstrated an ability to 
recolonize after fire events on Otay Mountain, and data obtained since 
publication of the 2010 90-day finding (75 FR 17062) indicate Thorne's 
hairstreak butterfly is able disperse through wind events between any 
temporarily isolated patches of H. forbesii (see Distribution and 
Population Status section above). Therefore, we have determined that 
habitat fragmentation is not a threat to the subspecies now, nor is it 
likely to become so in the foreseeable future.
Road and Firebreak Construction
    Thorne's hairstreak butterfly habitat is relatively protected from 
most sources of habitat destruction, modification, or

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curtailment because approximately 99 percent of its potential habitat 
(mapped Interior Cypress Forest vegetation; CNDDB GIS database 2007) is 
within publicly owned areas that are conserved and managed, primarily 
within the BLM Otay Mountain Wilderness and San Diego Multiple Species 
Conservation Program (MSCP) subarea plan preserves (see Habitat 
Conservation Plans (HCPs) and Natural Community Conservation Plans 
(NCCPs) section and Factor D discussion below).
    Although road and firebreak construction has occurred in the past 
in stands of Hesperocyparis forbesii where Thorne's hairstreak 
butterflies have been observed, these impacts have been relatively 
limited based on our qualitative comparison of Thorne's hairstreak 
butterfly and host plant locations with Google Earth satellite imagery 
of roads and firebreaks. Because U.S. Customs and Border Protection 
recently completed construction of the border fence and expanded the 
associated ``pack trail'' into a wider ``truck trail'' to accommodate 
vehicles, the need for further significant Border Patrol-related 
construction activities is not anticipated (Ford 2010, p. 1). Any 
future firebreak and road construction projects that do occur in 
Thorne's hairstreak butterfly habitat on Otay Mountain will be planned 
so as to minimize impacts to the butterfly (see also Factor D below), 
while reducing the threat of fire to the subspecies and its host plant 
by slowing the spread of fire once ignited (BLM 2010a, pp. 6-7). 
Finally, Williams and Congedo (2008, p. 19) concluded that existing 
traffic corridors on Otay Mountain did not appear to be detrimental to 
Thorne's hairstreak butterfly unless increasing human traffic 
contributes to increasing fire danger.
    The status of the Otay Mountain area as predominantly wilderness 
area and preserve (which are managed) indicates this area is unlikely 
to receive increased legal human traffic. Furthermore, as noted above, 
recent border fence construction and other enforcement activities in 
the Otay Mountain Wilderness area have reduced illegal human traffic 
(Ford 2010, p. 1), thereby reducing the likelihood of fire ignition by 
this source. Therefore, road and firebreak construction is not a 
significant threat to the subspecies now, nor is it likely to become so 
in the foreseeable future.
Habitat Conservation Plans (HCPs) and Natural Community Conservation 
Plans (NCCPs)
    Habitat conservation plans (HCPs) and natural community 
conservation plans (NCCPs) benefit Thorne's hairstreak butterfly 
through conservation, management, and monitoring. Habitat conservation 
plans are developed under section 10 of the Act to support issuance of 
permits that authorize the limited incidental take of listed species in 
return for conservation and management of the species and their 
habitats. The NCCP program is a cooperative effort involving the State 
of California and numerous private and public partners to protect 
regional habitats and species. The primary objective of NCCPs is to 
conserve natural communities at the ecosystem scale while accommodating 
compatible land uses. NCCPs help identify, and provide for, the 
regional or area-wide protection of plants, animals, and their habitats 
while allowing compatible and appropriate economic activity. Many NCCPs 
are developed in conjunction with HCPs prepared under the Act.
    The San Diego Multiple Species Conservation Program (MSCP) is a 
subregional HCP and NCCP made up of several subarea plans that has been 
in place for more than a decade. Under the umbrella of the MSCP, each 
of the 12 participating jurisdictions is required to prepare a subarea 
plan that implements the goals of the MSCP within that particular 
jurisdiction.
    Both Thorne's hairstreak butterfly and Hesperocyparis forbesii are 
covered species under the County of San Diego MSCP Subarea Plan, 
although neither the butterfly nor H. forbesii are covered species 
under the City of Chula Vista MSCP Subarea Plan. The County of San 
Diego MSCP Subarea Plan encompasses the majority (859 ac (348 ha)) of 
H. forbesii habitat (Interior Cypress Forest; CNDDB GIS database 2007) 
outside of the Otay Mountain Wilderness. The remainder of the H. 
forbesii habitat outside of the Otay Mountain Wilderness (approximately 
60 ac (24 ha)) is privately owned in an Amendment Area for the San 
Diego MSCP Planning Area (see discussion below). Within the County of 
San Diego MSCP Subarea Plan, over 99 percent of H. forbesii habitat 
(Tecate Cypress Forest) is planned for conservation and management 
(County of San Diego 2008a, Part 3, Section 2, p. 7), and the majority 
has already been acquired for conservation.
    As noted above, Thorne's hairstreak butterfly and Hesperocyparis 
forbesii are covered species under the subarea plan (Service 1998, p. 
6), which requires protection of Thorne's hairstreak butterfly host 
plants and local chaparral species used as nectar sources. The 
Framework Management Plan for the County of San Diego Subarea Plan 
under the MSCP (County of San Diego 2008b, p. 2; Framework Management 
Plan) requires the use of specific adaptive management techniques 
directed at the conservation and recovery of covered species, such as 
actions that assure wildfires do not occur too frequently in areas 
where species are sensitive to fire. The Framework Management Plan also 
provides for biological monitoring and preparation of an annual report, 
and based upon this review and biological monitoring effort, 
adjustments in the management goals can be made as necessary (County of 
San Diego 2008b, p. 2). Because Thorne's hairstreak butterfly is 
required to be conserved and adaptively managed and monitored under the 
County of San Diego Subarea Plan, we anticipate land management to 
protect Thorne's hairstreak butterfly and its habitat will continue to 
be implemented under the County of San Diego Subarea Plan.
    Additionally, the Memorandum of Understanding (MOU) on cooperation 
in habitat conservation planning and management issued by BLM in 1994, 
in conjunction with the development of the County of San Diego Subarea 
Plan under the MSCP (BLM 1994, pp. 1-8), also applies to the Otay 
Mountain Wilderness because it falls entirely within the boundary of 
this subarea plan. As outlined in the MOU (BLM 1994, p. 3), BLM is 
committed to managing their lands (i.e., Otay Mountain Wilderness) to 
``conform with'' the County of San Diego Subarea Plan, which in turn 
requires protection of Thorne's hairstreak butterfly's larval host 
plant, Hesperocyparis forbesii, and local chaparral species used as 
nectar sources. Therefore, protections provided by the County of San 
Diego Subarea Plan under the MSCP to Thorne's hairstreak butterfly and 
its habitat also apply to the Otay Mountain Wilderness.
    The 90-day finding (75 FR 17062; April 5, 2010) states, 
``Approximately 48 ac (19 ha) of Hesperocyparis forbesii habitat fall 
under the [County of San Diego Subarea Plan], which strives for fire 
management and prevention to restore the previous 25-year [burn return 
interval]''; however, we have since determined this statement is not 
accurate. The statement was based on the 1994 BLM South Coast Resource 
Management Plan that specifies a minimum planned 25-year burn return 
interval for controlled burns in H. forbesii habitat ``east of the 
Minewawa truck trail on the Otay Mountain [Wilderness]'' (BLM 1994, p. 
21). The Minewawa Truck Trail runs from the peak at Doghouse Junction, 
north to Otay Lakes Road, dividing the northern half of Otay Mountain 
into east and

[[Page 9999]]

west quarters. As discussed above, per an MOU, BLM has committed to 
manage its lands in a manner that complements the County of San Diego 
Subarea Plan; this management commitment was mistakenly attributed to 
that HCP in the 90-day finding. The 48-ac (19-ha) estimate was based on 
the area of H. forbesii stands mapped by Lucas (Forister and Lucas 
2009, pp. 1-2) and located outside the Otay Mountain Wilderness. 
Therefore, the 48-ac (19-ha) area estimate is not accurate with regard 
to the amount of H. forbesii habitat (see Distribution and Population 
Status section above) that is managed by the County of San Diego. Our 
estimate of the habitat managed by the County of San Diego under their 
subarea plan is 859 ac (348 ha) (see discussion above). Finally, BLM 
does not have any plans to conduct controlled burns (see Factor D 
discussion below) nor is it committed to maintain a 25-year burn return 
interval for such burns (BLM 1994, p. 21), and the County of San Diego 
Subarea Plan includes the assurance that wildfires will not occur too 
frequently in areas where species are sensitive to fire. The BLM draft 
revised South Coast Resource Management Plan specifically includes a 
goal of restoring burn return interval to 50 years through fire 
prevention or suppression and prescribed burns (see Factor D discussion 
below). Current BLM prescribed burn practices preclude burning of any 
H. forbesii habitat that would not enhance cypress stand viability or 
that would negatively affect Thorne's hairstreak butterfly (see Factor 
D discussion below). Therefore, the misrepresented regulatory 25-year 
burn return interval issue is not a valid concern with regard to 
Thorne's hairstreak butterfly conservation.
    The City of Chula Vista Subarea Plan under the MSCP includes a 
preserve that encompasses the newly discovered Otay River Valley 
occupied site (see Distribution and Population Status section above). 
Thorne's hairstreak butterfly and Hesperocyparis forbesii are not 
covered species under this subarea plan. However, all lands preserved 
under the Chula Vista Subarea Plan are adaptively managed and 
maintained to:
    (1) Ensure the long-term viability and sustainability of native 
ecosystem function and natural processes throughout the Preserve;
    (2) Protect existing and restored biological resources from the 
impacts of human activities within the Preserve while accommodating 
compatible uses;
    (3) Enhance and restore, where feasible, appropriate native plant 
associations and wildlife connections to adjoining habitat to provide 
viable wildlife and sensitive species habitat;
    (4) Facilitate monitoring of selected target species, habitats, and 
linkages to ensure long-term persistence of viable populations of 
priority plant and animal species; and
    (5) Ensure functional habitats and linkages for those species 
(Service 2003b, pp.18, 70, FWS-SDG-882.1).
    We believe these management prescriptions adequately protect 
Thorne's hairstreak butterfly and its habitat within the preserve, and 
the adaptive management measures of the Chula Vista Subarea Plan allow 
for adjustment of preserve management, as appropriate, to conserve this 
newly discovered population of Thorne's hairstreak butterfly.
    One relatively small area of occupied cypress forest (approximately 
60 ac (24 ha) composed of four butterfly observation locations) in the 
southwest foothills of Otay Mountain east of Otay Mesa is privately 
owned and not within an approved subarea plan, but falls within the 
MSCP planning area where a new subarea plan is being developed (i.e., a 
County of San Diego MSCP ``Amendment Area'') (CNDDB GIS Database 2010). 
While these habitats are not currently protected from threats to 
Thorne's hairstreak butterfly habitat by conservation or management, 
the majority of this area is also occupied by the endangered Quino 
checkerspot butterfly (Euphydryas editha quino), and Thorne's 
hairstreak butterfly habitat is therefore already afforded some 
indirect protection under section 9 of the Act.
Summary of Factor A
    We evaluated several factors with the potential to destroy, modify, 
or curtail Thorne's hairstreak butterfly's habitat or range, including 
decreasing burn return intervals, climate change related to wildfire, 
habitat fragmentation, and road and firebreak construction. We also 
evaluated the benefits to Thorne's hairstreak butterfly and its habitat 
associated with HCPs and NCCPs. Wildfire can negatively affect the 
species' habitat and in particular its host plant. However, our 
analysis does not indicate wildfire events have deviated from 
historical fire frequency or burn return interval patterns. Despite two 
recent large fires (2003 and 2007), Thorne's hairstreak butterfly has 
not only survived or recolonized habitats within mapped recent fire 
perimeters, it has expanded its range. In addition, while uncertainty 
exists regarding the potential effects of climate change on wildfire 
and habitat loss, the best available information regarding decreased 
burn return interval indicates the indirect effects of climate change 
on Thorne's hairstreak butterfly habitat are not threats to the 
subspecies now, nor are they predicted for the future. We have also 
determined the best available information indicates habitat 
fragmentation does not occur within the range of Thorne's hairstreak 
butterfly. We further determined that impacts to Thorne's hairstreak 
butterfly habitat resulting from road and firebreak construction have 
been relatively limited and are not anticipated to increase in the 
future. Additionally, approximately 99 percent of all potential 
Thorne's hairstreak butterfly habitat (cypress woodland within existing 
County of San Diego Subarea Plan preserves, the City of Chula Vista 
Subarea Plan preserve, and Otay Mountain Wilderness Area) is conserved 
and managed to benefit both the species and its host plant. Therefore, 
we believe existing HCPs and NCCPs provide protection for Thorne's 
hairstreak butterfly habitat. Based on our review of the best available 
scientific and commercial information, we conclude that Thorne's 
hairstreak butterfly is not threatened by the present or threatened 
destruction, modification, or curtailment of its habitat or range now 
or in the foreseeable future.

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

    We have no information to indicate that overutilization for 
commercial, recreational, scientific, or educational purposes is 
currently a threat to the Thorne's hairstreak butterfly, nor do we 
anticipate that it will become a threat in the future. Therefore, based 
on our review of the best available scientific and commercial 
information, we conclude that Thorne's hairstreak butterfly is not 
threatened by overutilization for commercial, recreational, scientific, 
or educational purposes now or in the foreseeable future.

Factor C. Disease or Predation

Disease
    Our review of the best available scientific and commercial data 
found nothing to indicate that disease is a threat to Thorne's 
hairstreak butterfly now or in the foreseeable future.
Predation
    Predation (including parasitism) is a factor that is known to cause 
mortality in butterflies, and therefore could potentially threaten any 
butterfly

[[Page 10000]]

species. Faulkner and Klein (2005, p. 34) stated that birds may consume 
Thorne's hairstreak butterfly larvae, although we are not aware of any 
data that indicate bird predation is a significant threat to Thorne's 
hairstreak butterflies. Brachonid wasps (parasitoid insects that 
deposit eggs in their host and kill it when offspring emerge as adults) 
have been observed near the host plant, but there has been no 
documentation of predation on Thorne's hairstreak butterflies (Faulkner 
and Klein 2005, p. 34; Klein 2010a p, 5). One potential larval predator 
observed during the 2007 season in large numbers at one occupied site 
is the nonnative seven-spotted ladybird beetle (Coccinella 
septempuctata) (Klein 2010a, pp. 5, 12); however, we are not aware of 
any data indicating the beetles have negative effects on Thorne's 
hairstreak butterfly.
    Heavy predation and parasitism of adult insects and their progeny 
is a common ecological phenomenon, and most species have evolved under 
conditions where high mortality due to natural enemies has shaped their 
evolution (see Schmid-Hempel 1995, p. 255; Ehrlich et al. 1998). Our 
review did not reveal any specific information regarding predation of 
Thorne's hairstreak butterflies, nor do we have any indication that 
predation will become a threat in the foreseeable future. Therefore, 
based on our review of the best available scientific and commercial 
information, we conclude Thorne's hairstreak butterfly is not 
threatened by predation either now or in the foreseeable future.

Factor D. The Inadequacy of Existing Regulatory Mechanisms

    The Act requires us to examine the adequacy of existing regulatory 
mechanisms with respect to threats that may place Thorne's hairstreak 
butterfly in danger of extinction or likely to become so in the future. 
Existing regulatory mechanisms that may have an effect on potential 
threats to Thorne's hairstreak butterfly can be placed into two general 
categories: (1) Federal mechanisms, and (2) State mechanisms.
Federal Mechanisms
    The Otay Mountain Wilderness Act (1999) (Pub. L. 106-145) and BLM 
management policies provide protection for the majority of occupied 
Thorne's hairstreak butterfly habitat (over 90 percent of all recorded 
butterfly observation locations). The Otay Mountain Wilderness Act 
directs that the Otay Mountain designated wilderness area (i.e., Otay 
Mountain Wilderness; 18,500 ac (7,486 ha)) be managed in accordance 
with the provisions of the Wilderness Act of 1964 (16 U.S.C. 1131 et 
seq.). The Wilderness Act of 1964 strictly limits use of wilderness 
areas, imposing restrictions on vehicle use, new developments, 
chainsaws, mountain bikes, leasing, and mining, in order to protect the 
natural habitats of the areas, maintain species diversity, and