[Federal Register: August 8, 2006 (Volume 71, Number 152)]
[Proposed Rules]
[Page 44980-44988]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr08au06-29]
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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 Thorne's Hairstreak 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 U.S. Fish and Wildlife Service (Service), announce a
90-day finding on a petition to list the Thorne's hairstreak butterfly
(Callophrys [Mitoura] grynea thornei or Callophrys [Mitoura] thornei)
as an endangered species under the Endangered Species Act of 1973, as
amended. We find the petition does not provide substantial scientific
or commercial information indicating the requested action is warranted.
Therefore, we will not initiate a further status review in response to
this petition. We ask the public to submit to us any new information
that becomes available concerning the status of the Thorne's hairstreak
butterfly or threats to it.
DATES: The finding announced in this document was made on August 8,
2006.
ADDRESSES: The complete file for 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, Carlsbad, CA 92011. New information, materials,
comments, or questions concerning the Thorne's hairstreak butterfly may
be submitted to us at any time at the above address.
FOR FURTHER INFORMATION CONTACT: Jim Bartel, Field Supervisor, Carlsbad
Fish and Wildlife Office (see ADDRESSES section above), 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, 24 hours a day, 7
days a week.
SUPPLEMENTARY INFORMATION:
Background
Section 4(b)(3)(A) of the Endangered Species Act (Act) (16 U.S.C.
1531 et seq.) requires that we make a finding on whether a petition to
list, delist, or reclassify a species presents substantial information
to indicate that the petitioned action may be warranted. To the maximum
extent practicable, this finding is to be made within 90 days of
receipt of the petition, and the finding is to be published in the
Federal Register.
This finding summarizes information included in the petition and
information available to us at the time of the petition review. A 90-
day finding under section 4(b)(3)(A) of the Act and Sec. 424.14(b) of
our regulations is limited to a determination of whether the
information in the petition meets the ``substantial information''
threshold. Substantial information 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)).
Previous Federal Action
The Thorne's hairstreak butterfly was included as a Category 2
candidate species in our November 21, 1991 (56 FR 58804), and November
15, 1994 (59 FR 58982), Candidate Notices of Review (CNOR). Category 2
included taxa for which information in the Service's possession
indicated that a proposed listing rule was possibly appropriate, but
for which sufficient data on biological vulnerability and threats were
not available to support a proposed rule. In the CNOR published on
February 28, 1996, the Service announced a revised list of plant and
animal taxa that were regarded as candidates for possible addition to
the List of Threatened and Endangered Species (61 FR 7595). The revised
candidate list included only former Category 1 species. All former
Category 2 species were dropped from the list in order to reduce
confusion about the conservation status of these species, and to
clarify that the Service no longer regarded these species as candidates
for listing. Since the Thorne's hairstreak butterfly was a Category 2
species, it was no longer recognized as a candidate species as of the
February 28, 1996, CNOR.
On June 4, 1991, the Service received a petition dated May 27,
1991, from David Hogan of the San Diego Biodiversity Project to list
the Thorne's hairstreak butterfly, Hermes copper butterfly
(Hermelycaena [Lycaena] hermes), Laguna Mountains skipper (Pyrgus
ruralis lagunae), and Harbison's dun skipper (Euphyes vestries
harbinsoni) as endangered under the Act. In a Federal Register notice
dated July 19, 1993 (58 FR 38549), the Service announced its finding on
the petition. We found that the petition presented substantial
information for the Laguna Mountains skipper, but not for the other
three butterflies. However, the finding also concluded that other
substantial information existed to support a
[[Page 44981]]
decision that listing may be warranted for the other three butterflies,
including the Thorne's hairstreak butterfly, and announced our
intention to continue the formal status review of these species. In a
proposed rule for the Laguna Mountain skipper and Quino checkerspot
butterflies published on August 4, 1994 (59 FR 39869), the Service
clarified that the negative 90-day finding on the Thorne's hairstreak
butterfly and the other two butterflies ``was made because sufficient
information was not available regarding the threats to and biological
vulnerability of these'' butterflies. Though we have continued and will
continue to collect available data on the Thorne's hairstreak butterfly
and the other two butterflies, we did not complete the status review of
Thorne's hairstreak butterfly pursuant to section 4(b)(3)(A) of the
Act.
On October 25, 2004, the Service received an updated petition to
list the Thorne's hairstreak and Hermes copper butterflies as
endangered from David Hogan of the Center for Biological Diversity.
Petitioners also sought emergency listing protection for Thorne's
hairstreak and designation of critical habitat for both butterfly taxa
concurrent with listing, if warranted. Included in the petition was
information regarding the subspecies's taxonomy, biology, ecology,
historical and current distribution, present status, and potential
causes of decline and imminent threats. In a letter dated May 9, 2005,
the Service determined that despite apparent threats to Thorne's
hairstreak butterfly, such threats did not appear to be of a magnitude
and severity to warrant emergency listing. In our response, we also
advised the petitioners that we had insufficient funds to respond to
the petitions at that time. On March 15, 2005, we received a 60-day
notice of intent to sue filed by the Center for Biological Diversity
for lack of response to the Thorne's hairstreak and Hermes copper
butterfly petitions. On October 18, 2005, the Center for Biological
Diversity filed a complaint for declaratory and injunctive relief
challenging our failure to make the required 90-day findings on these
two petitions. The Service agreed to submit 90-day petition findings on
Thorne's hairstreak and Hermes copper butterflies to the Federal
Register by August 1, 2006, and if the 90-day findings determined that
listing may be warranted, to submit 12-month findings to the Federal
Register by June 1, 2007. This notice constitutes our 90-day finding on
the petition to list the Thorne's hairstreak butterfly. The 90-day
finding on the petition to list the Hermes copper butterfly will be
published in the Federal Register separately.
In completing this 90-day finding, the Service has reviewed not
only the information submitted in the petition, but also information in
our files. This includes all of the data we had obtained prior to the
July 19, 1993, not substantial finding that would have been considered
in any internal status reviews had one been completed, as well as all
of the information we have continued to collect on this species to
date. Based on all new information and our analysis below, we have
determined that the petition does not present substantial scientific or
commercial information indicating that listing the Thorne's hairstreak
butterfly may be warranted or that a status review or status assessment
should be conducted.
Taxonomy
Thorne's hairstreak butterfly (Mitoura thornei) was originally
described by John Brown (1983) based on a specimen collected by Fred
Thorne in 1972, near Lower Otay Lake, which is generally west of Otay
Mountain. Brown distinguished M. thornei from its closest relative M.
loki on the basis of host preference (cypress (Cupressus) versus
juniper (Juniperus)), the color of the ventral hindwing surface (green
versus purple), and geographical isolation.
Brown (1983) described Thorne's hairstreak butterfly at the species
rank, which has been accepted by many subsequent authors (Garth and
Tilden 1986; Ballmer and Pratt 1988; Emmel et al. 1998; Opler and
Warren 2004). However, some authors disagree with this classification.
Shields (1984) considers Thorne's hairstreak butterfly a subspecies of
M. loki, and Scott (1986) lists it as a subspecies of the Cedar
hairstreak (Callophrys gryneus). The issue of the taxonomic ranking and
placement of Thorne's hairstreak butterfly was considered by the
Committee on Scientific Names of North American Butterflies in 1999.
The committee adopted the recommendation made by Dr. Robert K. Robbins,
an expert on Lycaenidae (Research Entomologist with U.S. Department of
Agriculture's Systematic Entomology Laboratory at the National Museum
of Natural History, Smithsonian Institution), that both M. loki and M.
thornei should be treated as belonging to the superspecies, C. gryneus
(Faulkner and Klein 2005). Currently, the committee's Checklist of
North American Butterflies (North American Butterfly Association (NABA)
2004) includes M. thornei and M. loki as Callophrys gryneus thornei and
Callophrys gryneus loki, respectively.
The petitioner deferred to other experts regarding the appropriate
classification, taxonomic rank, of Thorne's hairstreak butterfly (i.e.,
species or subspecies). In 2004, the Service contracted with Dr.
Richard W. Van Buskirk (Pacific University in Forest Grove, Oregon) to
review the taxonomic status of Thorne's hairstreak butterfly. Following
Van Buskirk's recommendation (Van Buskirk 2004), the Service recognizes
Thorne's hairstreak butterfly as the subspecies Callophrys gryneus
thornei.
Description
Adult Thorne's hairstreak butterflies are approximately 1.0 to 1.2
inches in wingspan (25.4 to 30.5 millimeters) (Brown 1983). The
forewings and hindwings are rich reddish brown with dark brown shading
on the margin. The ventral surface forewing is mahogany brown with
traces of lavender overscaling. The males bear well-developed scent
pads on the forewings, and the hindwings are tailed. Eggs are round
(echinoid), light green, and laid singly on the food plant. Garth and
Tilden (1986) provide a description of the butterfly's early stages.
The Thorne's hairstreak butterfly is bivoltine (has two flight
periods per year) and overwinters in the pupal stage. The pupation time
for first generation is about 10 to 15 days, with emergence occurring
in late February through March or possibly early April, depending on
rainfall. The second generation emerges in June. A third brood may take
place in September if summer rains occur (Faulkner and Klein 2005).
Eggs incubate in 7 to 14 days. The first instar larvae initially
bore into the young stems of the host plant, Tecate cypress (Cupressus
forbesii), but later become external feeders. Pupation is in the duff
and leaf litter at the base of the host plant, and larvae feed on young
cypress stems. Mature larvae are vivid green with two irregular white
crescents on each segment, forming a longitudinal white stripe along
each side of the larvae (Faulkner and Klein 2005).
Conifer-eating larvae within family Lycaenidae are an unusual
occurrence. Within San Diego County, its congeners Callophrys gryneus
loki (juniper hairstreak) and Callophrys nelsoni (Nelson's hairstreak)
have only been found in association with California juniper (Juniperus
californica) and incense cedar (Calocedrus decurrens) host plants,
respectively (Faulkner and Klein 2005).
[[Page 44982]]
Habitat
According to Brown (1983), Thorne's hairstreak butterfly is
restricted to its larval host plant, Tecate cypress. Associated with
chaparral ecosystems in southern California and northern Baja
California, Tecate cypress occurs primarily on north-facing slopes from
near sea level to over 4,200 feet (ft) (1,300 meters (m)) in elevation
(Dunn 1986). Although some experts hypothesized that larvae eat only
mature Tecate cypress at least 25 to 30 years old (Klein and Williams
2003; Faulkner and Klein 2005), recent post-fire observations of adults
in three stands of cypress trees less than 9 years old within a 1996
fire footprint (Faulkner and Klein 2005) do not support that
hypothesis. Thus, the best available information indicates Thorne's
hairstreak butterflies can use host plants as young as 9 years of age.
Adult Thorne's hairstreak butterflies are known to nectar on
Eriogonum fasciculatum (California buckwheat), Ceanothus tomentosus
(Ramona lilac), and Lotus scoparius (deerweed), in the vicinity of
Tecate cypress stands (Faulkner and Klein 2005).
Thorne's hairstreak butterfly dispersal behavior is not well known.
An individual was observed nectaring on deerweed plants 0.25 miles (mi)
(0.4 kilometer (km)) away from the nearest Tecate cypress (Faulkner and
Klein 2005). Adults have been observed nectaring on California
buckwheat as much as 197 ft (60 m) away from Tecate cypress trees
(Faulkner and Klein 2005). Mattoni (1998) gave estimated relative
movement values for three species of Callophrys butterflies in the
greater Los Angeles area. Two species were estimated to move between
330-3300 ft (100-1000 m), and one from 3300 ft to 30 mi (1-50 km).
Among butterflies, the genus Callophrys appears to be relatively
sedentary.
Historical and Current Range/Distribution
Thorne's hairstreak butterfly is known only from the vicinity of
Otay Mountain in southern San Diego County, California, in association
with its larval host plant, Tecate cypress. Though not common within
the limits of its range, Tecate cypress occurs in widely scattered and
isolated ``floristic islands'' in the chaparral of southern California
and Baja California Norte (Griffin and Critchfield 1972; Dunn 1986;
Minnich 1987). In California, Tecate cypress is found on Guatay
Mountain, Otay Mountain, and Tecate Peak in San Diego County; and on
Sierra Peak and in Coal Canyon in Orange County (Dunn 1986).
Historically, the Thorne's hairstreak butterfly has been reported
on Otay Mountain in San Diego County, primarily in Little Cedar Canyon
and Cedar Canyon (Klein and Williams 2003). An unconfirmed historic
observation of the subspecies in Orange County on private land has been
reported (R. Stanford pers. comm. in Faulkner and Klein 2005).
Multiple, consecutive surveys over 10 years within areas containing
Tecate cypress on Tecate Peak and Guatay Mountain in San Diego County
and some stands in Baja California, Mexico, conducted annually during
the late 1980s and early 1990s, did not yield any Thorne's hairstreak
butterflies (Anderson 2003). However, we do not have documentation of
these surveys and are unable to determine what proportion of the Tecate
cypress stands on Tecate Peak and Guatay Mountain in San Diego County
were surveyed. Therefore, it is unclear whether these surveys efforts
constitute comprehensive surveys of the Tecate cypress stands in these
areas. Limited sampling in the Sierra Peak-Coal Canyon area in Orange
County did not yield any Thorne's hairstreak butterfly observations
(Brown 1983).
More than 20 groves of Tecate cypress are documented by botanical
collections or aerial imagery from Baja California Norte, Mexico,
indicating potential distribution of the Thorne's hairstreak butterfly
in Mexico. Minnich (1987) described the northernmost stands of Tecate
cypress in Mexico as extensions of U.S. populations at the border. As
stated above, some surveys have been conducted in Tecate cypress stands
in Baja California, Mexico for Thorne's hairstreak butterflies during
the late 1980's and early 1990's. However, since we do not have
documentation of these surveys, it is unclear what proportion of the
Tecate cypress stands in Baja were surveyed. Therefore, more
investigation is required to determine the possible extent of
undiscovered populations of Thorne's hairstreak butterfly in Tecate
cypress stands in Mexico.
Population Estimates/Status
No specific data on Thorne's hairstreak butterfly abundance or
population dynamics and distribution exists, although a number of
apparently discrete occupied locations have been identified. The
petition states that fewer than 10 historically occupied locations have
been identified on Otay Mountain (Klein and Williams 2003) primarily
within designated wilderness administered by the Bureau of Land
Management (BLM). The status of Thorne's hairstreak butterfly and its
habitat (areas dominated by Tecate cypress over 6 ft (2 m) tall) was
evaluated as part of a post-2003 Otay/Mine fire reassessment of species
covered by the section 10(a)(1)(B) permit associated with the San Diego
Multiple Species Conservation Plan (MSCP). Surveys of Tecate cypress
stands conducted in 2004 revealed the presence of 4 to 5 areas occupied
by the subspecies (Martin 2004; Klein 2006). However, Martin (2004) and
Klein (2006) acknowledge that not all cypress stands were surveyed due
to accessibility. No quantitative data on population size exist.
Threats Analysis
In the following discussion, we respond to each of the major
assertions made in the petition, organized by the Act's listing
factors. 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 species. A species may be determined to be
endangered or threatened due to one or more of the five factors
described in section 4(a)(1) of the Act. The five listing factors are:
(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; and
(E) other natural or manmade factors affecting its continued existence.
This 90-day finding is not a status assessment and does not
constitute a status review under the Act. A brief discussion of how
each of the five listing factors applies to the Thorne's hairstreak
butterfly follows.
A. The Present or Threatened Destruction, Modification, or Curtailment
of Habitat or Range
The petition, its appendices, and referenced documents discuss the
following threats that we have grouped under Factor A: wildfire,
prescribed fire, grazing, and vehicle access and recreation.
Wildfire
Information provided by the petitioner. The petitioner asserts that
Thorne's hairstreak butterfly is highly and immediately vulnerable to
extinction due to the threat of wildfire as a result of direct
mortality of individuals and indirect mortality due to loss of the
subspecies' larval host plant, Tecate cypress. (The threat of wildfire
as it relates to direct mortality of individual butterflies is
discussed under Factor E.) They assert that one
[[Page 44983]]
single new fire could cause the extinction of this butterfly. The 2003
Otay/Mine fire served as an example of the threat of fire to the
butterfly when it burned 68 percent of the Thorne's hairstreak
butterfly habitat (Betzler et al. 2003). The petitioner claims the
number of fires greatly exceeds natural fire frequencies in southern
California's chaparral ecosystems, and the excessive fires have reduced
stands of mature Tecate cypress utilized by Thorne's hairstreak
butterflies.
The petitioner provided a map illustrating multiple fires that have
burned through and near Thorne's hairstreak butterfly locations within
the last century. According to the petition, increased human
populations and utilization of wildlands correlates with increased
southern California wildfire frequency (Keeley et al. 1999; Keeley 2001
[document not submitted with petition]; Keeley and Fotheringham 2003;
Wells et al. 2004).
The petitioner cited two references, Brooks et al. (2002 [correct
citation 2004]) and Keeley and Fotheringham (2003), which provide
examples where excessive fire harms chaparral ecosystems and dependent
species in a number of ways. The petition quoted Keeley and
Fotheringham (2003), ``* * * ecosystem health of shrublands is
threatened not by lack of fire but by high fire frequencies that exceed
the resilience of many species.'' The petitioner claims that excessive
fire contributes to expansion of highly flammable, invasive, alien
grasses (D'Antonio and Vitousek 1992) and forbs, contributing in turn
to an even greater fire frequency. Excessively frequent fire (more than
once a decade) may prevent nonsprouting chaparral shrubs from reaching
maturity, thereby eliminating these species entirely from the system
(Keeley and Fotheringham 2003).
According to the petitioners, frequent fire also leads to type
conversion and replacement of chaparral ecosystems with alien plant
species (Keeley 2001; Keeley and Fotheringham 2003). The petitioner
asserted that fire-induced conversion of Tecate cypress and surrounding
chaparral to vegetation dominated by invasive plant species reduces
Thorne's hairstreak butterfly habitat through loss of host and nectar
plants. Moreover, the petitioner reported that Zedler et al. (1983)
documented vegetation conversion in the San Ysidro Mountains within 1
mi of Thorne's hairstreak butterfly populations. Based on a personal
communication with Michael Klein, a Thorne's hairstreak butterfly
expert, the petitioner also refers to anecdotal observations that
exotic grasses and forbs appear to be increasing in former Tecate
cypress habitat following the 2003 fire.
Analysis of the information provided in the petition and available
to us at the time of petition review. Though cypress trees do not
survive fire, fire is integral to initiating cone opening and seed
dispersal and is, therefore, critical for successful regeneration of
Tecate cypress stands (Zedler 1977; Dunn 1986). Cone production begins
as early as 5 to 7 years of age, but is sporadic until the trees reach
about 30 years of age, and maximum cone production may not be achieved
until 50 years or later (Zedler 1981; Dunn 1986). For cypress
population levels to be maintained, the interval between fires must be
long enough to permit enough trees to produce sufficient cones and
seeds to replace the trees consumed in the fire. Zedler (1981) noted
that if [all] stands of Tecate cypress were burned every 33 years, his
``data suggest that near extinction would result after three or four
fires. Cone and seed production depend on factors other than age alone
and a large variation in average tree size and hence cone production
exists within stands.''
Faulkner and Klein (2005) agreed with Brown (1993) who stated that,
``[c]haparral fires probably represent the greatest threat to * * *
[Tecate cypress] and its associated insect fauna, including Thorne's
hairstreak butterfly.'' Though human-induced ignitions have been a part
of the California landscape for more than 10,000 years, humans ``likely
have had a greater influence in the twentieth century due to the near
exponential rise in population density and fire frequency in the
southern part of the state'' (Keeley and Fotheringham 2003). The
frequency of smaller fires proximal to the Mexican Border may have
increased on Otay Mountain, and, as the petitioner claims, this may be
due to increasing ignition by illegal immigrants and associated border
patrol activities since the 1990s (Jacob 1999, California Department of
Forestry and Fire prevention (CDF) 2006). For example, in 2004, over
100 fires were reported on Otay Mountain (Woychak 2006). However, the
majority of these fires were relatively small and localized (Porter
2006) and only affected small percentages of areas likely to be
Thorne's hairstreak habitat patches associated with Tecate cypress.
The majority of the studies examining the impacts of fire frequency
on California plant communities have focused primarily on overall
impacts to dominant vegetative types, such as coastal sage scrub,
chaparral, hardwood conifer forest, conifer forest, shrublands, and
desert shrublands (Zedler 1981; Zedler et al. 1983; Keeley et al. 1999;
Keeley and Fotheringham 2003; Wells et al. 2004). In a GIS modeling
study, Wells et al. (2004) largely concurred with Keeley et al (1999)
that increasing human population (especially at lower elevations) has
resulted in a greater number of fires and an increase in area burned
overall in Southern California. However, looking at fire frequency for
chaparral in San Diego County specifically, Wells et al. (2004)
concluded that the ``trend in burning in chaparral is virtually flat
over the past century, and if the years following 1950 are considered,
there has been a marked decrease in area burned since then.''
Few studies have examined the association between fire frequency
and population dynamics of Tecate cypress specifically. Dunn (1985,
1986) concluded at the time of his work in the 1980s that the Tecate
cypress population on Otay Mountain, the largest population in
California (about 5,900 acres (2,400 hectares)), was ``in no immediate
danger'' and that ``a fire would do little damage'' because the
majority of the trees were over 40 years old and the threat of fire
associated with the human interface was relatively low. In fact, Dunn
(1984) had concluded in his Master's thesis that, at that time, no need
existed for strict fire exclusion on Otay Mountain. As stated above,
increasing human population has resulted in a greater number of fires
in California. However, while portions of the Tecate cypress stands on
Otay Mountain were burned in 1996 and again in the 2003, no recent data
exist documenting the actual extent of impact to Tecate cypress
specifically. Although Zedler and others (1983) documented a decline in
native shrub abundance with the introduction of annual ryegrass (Lolium
multiflorum) following two fires in 1979 and 1980 on Otay Mountain
(i.e., the petitioner's claim of type conversion in the San Ysidro
Mountains within 1 mi of Thorne's hairstreak butterfly populations),
this work did not involve Tecate cypress and is not applicable to the
species. Moreover, in a recent study of the fire frequency and
population trend in four Tecate cypress populations in California,
cited on page 9 of the petition (cited as ``Ansary in print ''), de
Gouvenain and Ansary (in press) reported that the Otay Mountain, Tecate
Peak, and Guatay populations ``appeared to be stable or potentially
increasing'' (i.e., the rate of population increase or [lgr] > 1),
while only the Coal Canyon/Sierra Peak population in Orange County
``appeared to be
[[Page 44984]]
declining'' due to a shorter fire interval at that site.
We used GIS data in our files to overlay Tecate cypress
distribution on the petition map illustrating multiple fires that have
burned through and near Thorne's hairstreak butterfly locations within
the last century, and determined the majority of Tecate cypress was
within one or two fire footprints during the 93 year period from 1910
to 2003. Therefore, information in our files does not support the claim
that the fire frequency is high relative to Tecate cypress reproductive
maturity.
As cited in the petition, 68 percent of the Thorne's hairstreak
butterfly habitat (Tecate cypress) burned during the 2003 Otay/Mine
fire, a reduction from 5,577 ac (2,257 ha) to 1,778 ac (720 ha)
according to preliminary estimates by Betzler et al. (2003).
Nonetheless, butterfly occupation was documented after the 2003 fire in
2004 and 2005, mostly on the southwest slope of the mountain within the
1996 burn area that did not burn in 2003 (Martin 2004; Faulkner and
Klein 2005; Klein 2006). While the fire footprint was estimated by
Betzler et al. (2003) to have covered 68 percent of the Tecate cypress
habitat on Otay Mountain, the amount of Tecate cypress that actually
burned is likely less. The source cited by Betzler et al. (2003) was a
report prepared by the Interagency Burned Area Emergency Response Team
(IBAERT 2003), which gives vegetation mortality estimates in categories
of 0 to 25 percent, 26 to 75 percent, and greater than 76 percent. It
is not clear how Betzler et. al. (2003) calculated the 68 percent
burned habitat area, however it could have been based on the percent of
mapped Tecate cypress distribution within those burn categories given
by IBAERT (2003); therefore, Betzler et al. (2003) may not have known
how much Tecate cypress within the fire footprint was actually killed.
Limited post-fire monitoring in 2004 revealed the presence of at
least five unburned stands of mature Tecate cypress (defined for the
survey as a patch of at least 50 trees greater than 2 meters tall),
four of which were determined to be occupied by adult Thorne's
hairstreak butterflies at the time of the survey (Martin 2004). Two
areas adjacent to or within canyons known to contain Tecate cypress
were not surveyed in 2004. At least one area, the lower portion of
O'Neal Canyon may contain a significant stand since the upper portion
supports the largest stand of extant cypress (Martin 2004). According
to Martin (2004), these five stands constituted approximately 166 ac
(36 ha). However, since he was not able to survey all potential habitat
areas and his analysis was limited to stands of at least 50 mature
trees, additional stands and stands of less than 50 mature and immature
trees may have persisted after the fire.
Also, de Gouvenain and Ansary (in press) hypothesize that the steep
north-facing slopes and rocky outcrops where Tecate cypress is found
may function as refugia for Tecate cypress during fire events in the
surrounding chaparral habitat. A comprehensive survey of Tecate cypress
on Otay Mountain is needed in order to accurately determine the extent
of the impact caused by the 2003 fire and to what extent the Thorne's
hairstreak butterfly is utilizing the remaining Tecate cypress habitat
(at least 3,799 ac (1,537 ha)).
With regard to curtailment of habitat and range by fire, it is
important to consider that Thorne's hairstreak habitat distribution on
Otay Mountain is slightly greater than that of its larval host plant
(Tecate cypress), and must be based on adult resource use and movement
between and on the periphery of host plant stands. Given the
evolutionary relationship of Thorne's hairstreak and Tecate cypress
with fire, it is likely burned areas devoid of woody vegetation and
reduced butterfly population density after fire facilitate movement
between unburned host plant patches. For example, in a mark-recapture
study of Parnassius smintheus (Papilionidae) butterflies, Roland et al.
(2000) concluded ``butterflies move readily through open meadow but
that forests are twice as resistant to butterfly movement. Butterflies
also tended to stay at sites with high numbers of butterflies, but
readily emigrate from sites with small populations.'' Roland et al.'s
(2000) results are a good example of how differences in habitat
structure and population density can affect butterfly movement.
Differences in population densities and habitat structure are known to
commonly affect movement patterns of butterflies (Ries and Debinski
2001; Service 2003).
Along with the direct loss of Tecate cypress, the Thorne's
hairstreak butterfly's host plant, the petitioners claim that increased
fire frequency results in the conversion of Tecate cypress and
surrounding chaparral to vegetation dominated by invasive plant
species, further reducing the amount of host and nectar plants. As
discussed above, it appears that Tecate cypress populations on Otay
Mountain are stable and potentially increasing overall and that
frequency of fire in chaparral communities in San Diego County over the
past century is stable or potentially decreasing overall. Also,
although Zedler et al. (1983) documented a decline in native shrub
abundance following two fires in 1979 and 1980 on Otay Mountain, they
state that changes to the vegetative community following the 1979 fire
alone are similar to those commonly seen in chaparral fires. Their
study was not conducted in an area occupied by Tecate cypress. The
common pattern after chaparral fires is for native and introduced
annual herbs to dominate for the 1st year and then gradually decline as
the cover of shrub and subshrubs increases (Zedler et al. (1983). They
reported drastic reductions in several chaparral species, particularly
those with limited dispersal and specialized germination requirements,
after the same area that burned in 1979 burned again in 1980. However,
they state that over time, it is likely that coastal sage scrub
species, particularly those that are vigorous invaders of man-made and
natural disturbance, including Eriogonum fasciculatum, a nectar source
for Thorne's hairstreak butterfly, are likely to reoccupy the area.
Therefore, it is likely that while the vegetative community may undergo
short-term conversion, over time, native, fire adapted species will
reestablish.
In sum, information in the petition and available to us does not
substantiate a recent decline or downward trend in the extent of Tecate
cypress on Otay Mountain, the host plant of the Thorne's hairstreak
butterfly, as a result of increased fire frequency and associated alien
plant invasion.
Prescribed Fire
Information provided in the petition. The petitioner states that
while prescribed fire does not appear to be planned for the San Ysidro
Mountains, it could compound the threat of excessive fire to Thorne's
hairstreak butterflies and Tecate cypress if implemented in the future.
Analysis of information provided in the petition and available to
us at the time of petition review. No evidence exists to support the
petitioner's claim that prescribed burning would be allowed within the
Otay Mountain Wilderness. The current BLM policy is 100 percent fire
suppression on Otay Mountain (Woychak 2006).
Grazing
Information provided in the petition. The petitioner stated that
BLM authorizes grazing on Otay Mountain in an area occupied by Thorne's
hairstreak butterfly prior to the 2003 Otay/Mine fire and near the
``last five known remaining populations.'' The allotment is now vacant
according to agency staff,
[[Page 44985]]
but BLM is actively considering renewal of this grazing lease,
according to a Notice of Proposed Action dated May 26, 2004.
The petitioner claimed that renewal of the Otay Mountain grazing
allotment lease would result in significant direct and indirect effects
similar to those identified by the Service for the Quino checkerspot
butterfly (January 16, 1997; 62 FR 2313). The Quino checkerspot
butterfly recovery plan (Service 2003) noted that grazing may harm the
butterfly through destruction of larval host plants, soil compaction,
degradation of cryptogamic soil crusts, and trampling of eggs and
larvae. The invasion of alien plants may be facilitated by degradation
of soil crusts. The recovery plan recommends phasing out of commercial
grazing in Quino checkerspot butterfly's habitat.
The petitioner also stated that grazing on the Otay Mountain
allotment could harm the Thorne's hairstreak butterfly and Tecate
cypress even if grazing is excluded around existing populations of
these species because grazing could lead to the introduction of
invasive alien plants. These plants could increase fire frequency,
resulting in the loss of populations of sensitive species and habitat
degradation, and may result in subsequent further expansion of alien
plants through additional disturbance from fire.
Analysis of information provided in the petition and available to
us at the time of petition review. We confirmed that an active 5,522
acre (2,235 ha) BLM grazing allotment exists on Otay Mountain (Doran
2006) that overlaps occupied Thorne's hairstreak butterfly habitat.
Approximately one-third of Tecate cypress woodland on the mountain
(2,026 acres (820 ha)) occurs within the Otay Mountain Grazing
Allotment on the north side of the mountain (Anderson and Love 2006).
Approximately half (20 acres (8 ha)) of a patch of occupied mature
Tecate cypress trees was confirmed to be within the southern grazing
allotment boundary in 2004 (Anderson and Love 2006). However, the
grazing allotment is in a non-use status, which means that the allottee
does not intend to graze in the near term, and grazing is not allowed
in the Cedar Canyon Area of Critical Environmental Concern (Doran
2006). Also, Tecate cypress woodland would not often be very accessible
to cattle within the allotment, because of the extremely steep, thickly
vegetated terrain associated with Tecate cypress stands.
We were unable to confirm the petitioner's assertion that the
renewal of the grazing allotment lease will likely result in
significant direct and indirect harm to Thorne's hairstreak butterflies
and Tecate cypress populations. The petitioner failed to provide
specific examples of negative impacts from grazing on Thorne's
hairstreak butterflies and Tecate cypress. Comparison to Quino
checkerspot butterfly grazing threats is not appropriate because host
plants for that subspecies, unlike Tecate cypress, are herbaceous
annuals directly affected by grazing and type-conversion of open-canopy
vegetation.
Vehicle Access and Recreation
Information provided by the petitioner. The petitioner claims BLM's
emphasis on recreation in the San Ysidro Mountains, and maintenance of
vehicle access likely increases the risk of new fires. BLM lands
occupied by the subspecies are located within the agency's designated
Otay Mountain Wilderness. Roads grandfathered into the wilderness
designation generally allow unrestricted public access in close
proximity to Thorne's hairstreak butterfly populations except during
special closures.
Analysis of information provided in the petition and available to
us at the time of petition review. Although public access is allowed,
the Otay Mountain Wilderness is remote, and few people visit the
wilderness area. Because of the proximity of the wilderness area to the
United States-Mexico international border, border operations (e.g.,
surveillance and patrolling) are common throughout the wilderness.
Traffic is concentrated on few main roads adjacent to occupied Thorne's
hairstreak butterfly habitat. Border patrol vehicles and vehicles
accessing the wilderness may increase the risk of new fires; however,
fires that are potentially started by the border patrol would be
reported immediately. Since access by the public is rare, and border
patrol vehicle ignitions would be reported, we believe vehicle access
and recreation is not a significant threat to the subspecies. The
petitioner neglected to provide specific examples of vehicle access and
recreation increasing the risk of new fires to Thorne's hairstreak
butterfly habitat (i.e., Tecate cypress stands), and we are unaware of
any documentation that directly links vehicles and recreation as a
threat to this subspecies.
Because there is no clear threat of fire to Tecate cypress or
Thorne's hairstreak butterfly, and grazing and recreation impacts
appear negligible, we conclude that the petition and other available
information does not constitute substantial scientific information
indicating listing Thorne's hairstreak butterfly may be warranted due
to Factor A (destruction, modification, or curtailment of habitat or
range).
B. The Overutilization for Commercial, Sporting, Scientific, or
Education Purposes
The petitioner did not provide information with respect to Factor
B. We have no information regarding the overutilization for commercial,
sporting, scientific, or education purposes for Thorne's hairstreak
butterfly.
C. Disease or Predation
The petitioner did not provide any information with respect to
disease nor do we have any information regarding impacts of disease on
Thorne's hairstreak butterfly.
Predation
Information provided in the petition. The petitioner stated that
experts suspect birds, predatory insects, parasitic insects, and
spiders prey upon the Thorne's hairstreak butterfly. Birds may prey on
either larvae or adults. The harmful effects of otherwise normal
predation or parasitism might be exacerbated by population reduction
from excessive fires.
Analysis of information provided in the petition and available to
us at the time of petition review. The petitioner did not provide
specific information, nor was there any information available in our
files, documenting that the Thorne's hairstreak butterfly may be
endangered by predation.
D. The Inadequacy of Existing Regulatory Mechanisms
The petition and referenced documents discuss three regulatory
mechanisms that may provide some Thorne's hairstreak butterfly
conservation, including (1) the Wilderness Act, (2) BLM activities, and
(3) the San Diego Multiple Species Conservation Plan (MSCP).
Wilderness Act and BLM Activities
Information provided by the petition. While the petition
acknowledged BLM lands occupied by the subspecies are protected from
urban development and mining by the nature of the location within the
Otay Mountain Wilderness Area (designated under the Wilderness Act),
the petitioner asserted this area is not intensely managed, and BLM
does not implement proactive conservation measures for either the
Thorne's hairstreak butterfly or Tecate cypress. In addition, the
petitioner maintained that BLM does not recognize the Thorne's
hairstreak butterfly as a ``sensitive
[[Page 44986]]
[sub]species.'' The petitioner further claims Thorne's hairstreak
butterfly populations face an additional, unique risk of excessive fire
as U.S. border enforcement has inadvertently directed illegal Mexican
immigrant crossings away from coastal urban areas toward wildland areas
east of Otay Mesa. The petitioner contends that fire and land
management agencies often identify illegal immigrant's campfires and
arson as the cause of border-area wildfires.
Analysis of information provided in the petition and available to
us at the time of petition review. Congress formally designated BLM
lands on Otay Mountain as the Otay Mountain Wilderness in 1999 (Otay
Mountain Wilderness Act, December 11, 1999). The inclusion of these
occupied habitats within a designated Wilderness provided additional
significant protection for this area and complemented BLM's objective
to manage these public lands to provide protection and enhancement for
biological values. The Wilderness Act of 1964 (16 U.S.C. 1131)
restricts vehicles, new developments, chainsaws, mountain bikes,
leasing, and mining from the wilderness area.
As cited in the petition, BLM's South Coast Resource Management
Plan guides management and protection on sensitive species and their
habitat. At the time of the petition, BLM did not recognize Thorne's
hairstreak as a ``sensitive'' subspecies; however, the subspecies was
recently officially designated as ``sensitive,'' elevating it to a
higher management priority level (Schlachter 2006).
As stated in the petition, no formal plans to specifically manage
or monitor for Thorne's hairstreak butterfly currently exist. Thorne's
hairstreak butterfly populations may face an additional, unique risk of
excessive fire due to activities related to illegal Mexican immigrant
crossings east of Otay Mesa (Jacob 1999, CDF 2006). However, since at
this time it appears the primary source of the wildfire threat to the
subspecies is accidental wildfire caused by illegal immigrants, and
border security is currently greater than before to prevent illegal
immigration, fire prevention is indirectly maximized by border patrol
activities. Fire prevention measures include formation of the Border
Agency Fire Council, (BAFC) a multi-agency council formed due to the
wildfire threat to human life and the environment (Jacob 1999). The
goals of the BAFC are to make people in the border area aware of the
dangers of wildfire and encourage them to be careful with fire;
preferably not to start any campfires, but if they do, to understand
the fire must be completely out before they abandon it (CDF 2006). BAFC
member agencies represent a collaborative effort to prepare the area
for fire fighting purposes, including establishment of three helispots
and construction of spur roads (BAFC 2006). Signs in Spanish posted
across the mountain warn of the danger of starting campfires and advise
against it. Also, BLM's current policy is 100 percent fire suppression
on Otay Mountain (Woychak 2006). Therefore, while a formal management
plan would benefit the subspecies to guide long-term monitoring and
other types of conservation actions, it would not necessarily change
current fire prevention and suppression policies and activities.
San Diego MSCP
Information in the petition. The petitioner stated that the
Thorne's hairstreak butterfly is recognized as a ``covered species''
under the MSCP and some conservation activities in the San Ysidro
Mountains occur, but these activities do not appear to have reduced the
primary threats to the subspecies, especially from excessive wildfire.
Analysis of information provided in the petition and available to
us at the time of petition review. Thorne's hairstreak butterfly is
covered under the MSCP, and the MSCP recognizes that ``a fire
management program would be needed for prevention of catastrophic fires
and long term viability of its host plant.'' No fire management plan
has been written to date, nor has BLM developed a long-term management
or monitoring plan for the butterfly (J. Schlachter 2006). However, the
current BLM policy is 100 percent fire suppression on Otay Mountain;
BLM has received allocations to complete a wilderness management plan;
and a fire management plan is expected to be completed after the
wilderness plan and will focus on complete fuel suppression (Woychak
2006).
The Service considers the current BLM activities and policies, and
the MSCP adequate for protection of the subspecies. If the MSCP or
referenced activities and polices are modified in the future, the
adequacy of these measures to protect the Thorne's hairstreak butterfly
should be evaluated at that time. The Service does not believe the
absence of the cited plans poses a substantial threat such that the
Thorne's hairstreak butterfly requires additional regulatory mechanisms
to be developed. Therefore, the petition and other information in our
files does not present substantial information that the subspecies is
threatened at this time by the inadequacy of existing regulatory
mechanisms across all or a significant portion of its range.
E. Other Natural or Manmade Factors Affecting the Continued Existence
The petition, its appendices, and referenced documents discuss the
following threats that we have grouped under Factor E: wildfire,
habitat fragmentation, vulnerability of small and isolated populations,
and global climate change.
Wildfire
Information provided in the petition. The petitioner stated the
Thorne's hairstreak butterfly cannot escape fire. Pupae and larvae are
likely killed when fire burns Tecate cypress stands and nearby
chaparral. Adults are also likely killed by fire, due to their habit of
remaining close to their host plant, and the likelihood of their escape
being outpaced by an approaching fire. The petition claims excessive
fires over the last several decades have reduced Thorne's hairstreak
butterfly population numbers and disrupted metapopulation dynamics and
stability.
Analysis of information provided in the petition and available to
us at the time of petition review. The persistence of the Thorne's
hairstreak butterfly was considered questionable after the 2003 Otay/
Mine fire, since the fire footprint appeared to cover all areas known
to be occupied by the subspecies (Anderson 2003; Klein and Williams
2003). However, adult Thorne's hairstreak butterflies were documented
from four Tecate cypress stands after the 2003 fire on the southwest
slope of the mountain (Martin 2004; Faulkner and Klein 2005; Klein).
Therefore, as discussed under Factor A, it appears that some Tecate
cypress habitat did not burn during that fire and that the actual
extent of occupied habitat on Otay Mountain has not yet been
determined. The petition included a map delineating large fire
footprints from 1910 to 2003. We used GIS data in our files to overlay
all known occupancy records on the fire map and determined that 9 out
of the 12 Thorne's hairstreak butterfly observations (point data) and
the majority of Tecate cypress distribution are within one or two fire
footprints during the 93 year period from 1910 to 2003. The apparent
ability of Thorne's hairstreak butterflies to recolonize immature
Tecate cypress stands less than 9 years post-fire (Martin 2004;
Faulkner and Klein 2005; Klein), compared to the relatively low large-
fire frequency indicated by the petition map of less than 2 fires per
93 years, contradicts petition claims of a direct
[[Page 44987]]
mortality extinction threat due to high fire frequency on Otay
Mountain. Also, as discussed under Factor A, the steep canyons where
Tecate cypress is found may provide refugia during a fire.
While immature Thorne's hairstreak butterflies have not been
reported from younger stands surveyed after fire, this may be
attributed to the fact that they are small and cryptic, making them
difficult to detect, and spend most of their larval stage (early
instars) within the tissue of the Tecate cypress or buried as pupae in
the leaf litter on the ground. Also, post-fire monitoring has been
limited. We are only aware of post-fire monitoring being conducted in
2004. Therefore, additional monitoring would be needed to determine the
survival and recolonization rate of immature and adult butterflies
following a fire.
The petitioner did not provide information or data to substantiate
the claim that excessive fires over the last several decades have
reduced Thorne's hairstreak butterfly population numbers and disrupted
metapopulation dynamics and stability. As stated in the ``Population
Estimates/Status'' section of this finding, no quantitative data on
population size exists nor do we have any information on the dispersal
or movement behavior of this subspecies. Without this information, it
is not possible to determine the subspecies's population structure
(e.g., metapopulation or panmicitic) and subsequently, the impact of
fire on population numbers and structure.
Habitat Fragmentation
Information provided in the petition. The petitioner claimed
fragmentation of Thorne's hairstreak butterfly populations, through
fire, type conversion, and roads, poses a significant threat to the
subspecies. The petitioner noted that habitat fragmentation reduces the
area of Thorne's hairstreak butterfly habitat and isolates populations
from one another. In addition, the petitioner claimed that
fragmentation expands edge habitat, resulting in further stress on
fragmented or small populations.
Analysis of information provided in the petition and available to
us at the time of petition review. Neither the petition nor information
available support the claim that fragmentation threatens the subspecies
existence within its known distribution on Otay Mountain. The best
available information indicates Thorne's hairstreak butterfly is
capable of re-colonizing immature Tecate cypress stands in recently
burned areas. For example, as stated above, re-colonization of immature
stands after a 1996 fire has been documented (Faulkner and Klein 2005).
Also, as discussed above, surveys of potentially occupied habitat on
Otay Mountain are incomplete, and, as discussed under Factor A, habitat
patch distribution as defined by adult movement has not been
determined.
Vulnerability of Small and Isolated Populations
Information provided in the petition. The petitioner asserted that
endemic taxa such as the Thorne's hairstreak butterfly are generally
considered more prone to extinction than widespread species due to
their restricted geographic range. According to the petition, the
common factors that increase the vulnerability of small and isolated
populations to extinction are demographic fluctuations, environmental
stochasticity (i.e., random events), and reduced genetic diversity.
Analysis of information provided in the petition and available to
us at the time of petition review. Populations of Thorne's hairstreak
butterfly are likely subject to population fluctuations. If occupied
habitat is temporarily fragmented by fire, fluctuation in numbers could
render small populations more vulnerable to stochastic extirpation.
Small populations and isolation could subject the butterfly to genetic
drift and restricted gene flow that may decrease genetic variability
over time and could adversely affect the subspecies' viability.
However, we lack the genetic or demographic evidence to support such
claims in the petition, and potential isolation of small populations by
fire appears to be short-term. Furthermore, surveys of potentially
occupied habitat on Otay Mountain are incomplete and estimates of
population status/size do not currently exist. Therefore, information
in our files does not indicate small population size is a threat to
this subspecies.
Global Climate Change
Information provided in the petition. The petitioner asserted that
butterflies are particularly sensitive to small changes in
microclimates, such as fluctuations in moisture, temperature, or
sunlight. According to the petition, studies of Edith's checkerspot
(Euphydryas chalceona edithi) have verified speculation that whole
ecosystems may move northward or shift in elevation as the Earth's
climate warms (Parmesan and Galbraith 2004).
Analysis of the information provided in the petition and available
to us at the time of petition review. The petitioner did not provide
specific information validating the claim that the Thorne's hairstreak
butterfly may be endangered by global climate change. We recognize
recent evaluations by Parmesan and Galbraith (2004) that whole
ecosystems are seemingly being shifted northward. However, neither the
petition nor our files provides anything more than speculation on the
type, magnitude, or temporal effects of ecosystem changes that may be
brought about by regional climate change. We are not aware of any
documentation available or provided by the petitioner that directly
links global warming as a threat to the subspecies, or how global
warming specifically affects the subspecies. Therefore, we find that
the petition does not contain substantial information suggesting that
global climate change may be a factor that threatens the Thorne's
hairstreak butterfly.
Finding
We evaluated each of the five listing factors individually, and
because the threats to Thorne's hairstreak butterfly are not mutually
exclusive, we also evaluated the collective effect of these threats.
The petition focused primarily on three listing factors: Factor A (the
Present or Threatened Destruction, Modification, or Curtailment of the
Species' Habitat or Range), Factor D (Inadequacy of Existing Regulatory
Mechanisms), and Factor E (Other Natural or Manmade Factors Affecting
the Continued Existence). More specifically, information in the
petition suggests that fire poses the primary threat to Thorne's
hairstreak butterfly habitat and populations because the subspecies'
range occurs on lands susceptible to wildfires. However, it appears
that frequency of fire in occupied habitat over the past century is not
high enough on average to threaten the subspecies, and Tecate cypress
populations on Otay Mountain are stable and potentially increasing
overall. Within areas that have burned, the subspecies appears able to
re-colonize over time.
Also, we have determined that Federal regulations and activities
(Wilderness Act, BLM fire suppression policy, Border Patrol enforcement
activities, and MSCP) provide a significant level of protection for the
Thorne's hairstreak butterfly and/or its habitat on Federal lands that
include the subspecies entire known range. We will continue to work
with the City and County of San Diego and the BLM to avoid and minimize
impacts to the Thorne's hairstreak butterfly on their lands.
[[Page 44988]]
We have reviewed the petition and literature cited in the petition
and evaluated that information in relation to information available to
us. After this review and evaluation, we find the petition does not
present substantial scientific information to indicate listing the
Thorne's hairstreak butterfly may be warranted at this time. Although
we will not be commencing a status review in response to this petition,
we will continue to monitor potential threats and ongoing management
actions that might be important with regard to the conservation of the
Thorne's hairstreak butterfly across its range. We encourage interested
parties to continue to gather data that will assist with the
conservation of the subspecies.
References Cited
A complete list of all references cited herein is available, upon
request, from our Carlsbad Fish and Wildlife Office (see ADDRESSES
section above).
Author
The primary authors of this notice are staff from the Carlsbad Fish
and Wildlife Office (see ADDRESSES section above).
Authority
The authority for this action is the Endangered Species Act of
1973, as amended (16 U.S.C. 1531 et seq.).
Dated: August 1, 2006.
H. Dale Hall,
Director, Fish and Wildlife Service.
[FR Doc. E6-12743 Filed 8-7-06; 8:45 am]
BILLING CODE 4310-55-P