[Federal Register Volume 71, Number 219 (Tuesday, November 14, 2006)]
[Proposed Rules]
[Pages 66292-66298]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E6-19064]
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DEPARTMENT OF THE INTERIOR
Fish and Wildlife Service
50 CFR Part 17
Endangered and Threatened Wildlife and Plants; 12-Month Finding
on a Petition to List the Island Marble Butterfly (Euchloe ausonides
insulanus) as Threatened or 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 (Service), announce a
12-month finding on a petition to list the island marble butterfly
(Euchloe ausonides insulanus) under the Endangered Species Act of 1973,
as amended (Act). After review of all available scientific and
commercial information, we find that the petitioned action is not
warranted. Furthermore, the Service and the National Park Service (NPS)
have entered into a Conservation Agreement that implements conservation
measures specifically addressing the needs of the island marble
butterfly. We request that you submit any new information concerning
the status of and threats to this subspecies whenever it becomes
available. We will continue to collaborate with our partners to expand
the conservation efforts that have been instituted by several
landowners on currently occupied habitat.
DATES: The finding announced in this document was made on November 14,
2006.
ADDRESSES: You may send data, information, comments, or questions
concerning this finding to Ken Berg, Attn: Island Marble Butterfly,
Western Washington Fish and Wildlife Office, U.S. Fish and Wildlife
Service, 510 Desmond Drive, SE., Suite 102, Lacey, WA 98503; or via fax
to 360-753-9008. You may inspect the petition, administrative records,
supporting information, and comments received by appointment during
normal business hours at the above address.
FOR FURTHER INFORMATION CONTACT: Ted Thomas or Jodi Bush at the Western
Washington Fish and Wildlife Office (see ADDRESSES); or by telephone at
360-753-9440; or by fax at 360-753-9008; or by electronic mail at
[email protected].
SUPPLEMENTARY INFORMATION:
Background
On December 11, 2002, we received a petition dated December 10,
2002, requesting that we emergency list the island marble butterfly
(Euchloe ausonides insulanus) as an endangered species, and that we
designate critical habitat concurrently with the listing. The petition,
submitted by the Xerces Society, Center for Biological Diversity,
Friends of the San Juan, and Northwest Ecosystem Alliance, was clearly
identified as a petition for a listing rule and contained the names,
signatures, and addresses of the requesting parties. Included in the
petition was supporting information regarding the species' taxonomy and
ecology, historical and current distribution, present status, active
imminent threats, and potential causes of decline.
Section 4(b)(3)(B) of the Act (16 U.S.C. 1531 et seq.) requires
that, for any petition to revise the Lists of Threatened and Endangered
Wildlife and Plants that contains substantial scientific and commercial
information that listing may be warranted, we make a finding within 12
months of the date of the receipt of the petition on whether the
petitioned action is (a) Not warranted, (b) warranted, or (c)
warranted, but the immediate proposal of a regulation implementing the
petitioned action is precluded by other pending proposals to determine
whether any species is threatened or endangered, and expeditious
progress is being made to add or remove qualified species from the
Lists of Endangered and Threatened Wildlife and Plants. Section
4(b)(3)(C) of the Act requires that a petition for which the requested
action is found to be warranted but precluded be treated as though
resubmitted on the date of such finding, i.e., requiring a subsequent
finding to be made within 12 months. Each subsequent 12-month finding
will be published in the Federal Register.
Previous Federal Action
On January 22, 2003, we sent a letter acknowledging receipt of the
petition to Scott Hoffman Black, Executive Director of the Xerces
Society. In our response, we advised the petitioners that we had
insufficient funds to respond to the petition at that time and that we
would not be able to begin processing the petition in a timely manner.
On April 5, 2004, we received a 60-day notice of intent to sue for
three butterfly species, the Taylor's checkerspot (Euphydryas editha
taylori), the mardon skipper (Polites mardon), and the island marble
butterfly. On October 18, 2004, plaintiffs filed a complaint for
declaratory and injunctive relief, which specifically addressed
conservation actions needed for the island marble butterfly. Taylor's
checkerspot and mardon skipper butterflies were not addressed in that
complaint and are not assessed in this petition finding. We negotiated
a stipulated settlement agreement for the island marble butterfly,
dated February 28, 2005, in which we agreed to work cooperatively with
our conservation
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partners to conduct surveys and to assess the ecological needs of the
subspecies during 2005. We also agreed to submit a 90-day petition
finding to the Federal Register by February 5, 2006, and if necessary,
submit a 12-month finding to the Federal Register by November 5, 2006.
A 90-day finding was published in the Federal Register on February
13, 2006 (71 FR 7497). We found that the petition presented substantial
scientific information indicating that listing the island marble
butterfly may be warranted. Therefore, we initiated a status review of
the subspecies. A 60-day public comment period was opened, to allow the
public to provide information for the status review. This document
constitutes our 12-month finding on the island marble butterfly, and is
submitted in fulfillment of the stipulated settlement agreement.
On October 31, 2006, the Service and the NPS entered into a
``Conservation Agreement and Strategy for the Island Marble Butterfly
(Euchloe ausonides insulanus),'' that implements measures within San
Juan Islands National Historical Park specifically addressing the
conservation needs of the island marble butterfly.
Species' Description and Life History
The island marble butterfly is a member of the Pieridae family,
subfamily Pierinae. The island marble butterfly is 1.75 inches (4.5
centimeters) long, creamy white (Pyle 2002, p. 142; Guppy and Sheppard
2001, p. 159), and is larger than other subspecies of the large marble
butterfly (Euchloe ausonides). The yellow-green marbled pattern on the
ventral hindwings and forewings characterizes adults of the subspecies
(Pyle 2002, p. 142; Guppy and Sheppard 2001, p. 159).
The eggs of the island marble butterfly are bluish-greenish to
cream when laid (Pyle 2002, p. 142; Guppy and Sheppard 2001, p. 159),
and change to orange or red at maturity. Larvae have five instars
(developmental stages between each molt) before over-wintering as
pupae. Larvae are steely-blue above, transitioning to green below, with
bright yellow stripes along the sides and back, and are peppered with
small black spots (Pyle 2002, p. 142). Fifth-instar larvae walk about
to find secure resting locations for pupation on the lower stem of food
plants, where the pupae over-winter until emerging as adults the
following spring. The island marble butterfly is univoltine (the
subspecies has just one flight period per year) (Pyle 2002, p. 142;
Pyle 2003, p. 34). The flight period of adult butterflies generally
commences in early April and is completed by mid-June in the San Juan
Islands, Washington (Miskelly 2005, p. 5). Eggs may be observed for a
week beyond when adults are observed, and larvae have been observed
until early July (Miskelly 2005, p. 5).
Distribution and Status
Historically, the island marble butterfly has always been rare
(Guppy and Shepard 2001, p. 161). The subspecies was known from 14
museum records from collections made in British Columbia, Canada, from
1861 to 1908. The specimens are displayed in museum collections in
British Columbia, Canada, and the Smithsonian Institution, Washington,
DC. Historically, the island marble butterfly was only known from
Vancouver Island and the Canadian Gulf Islands, which are part of the
same geologic formation as the San Juan Archipelago. The island marble
butterfly was last observed on Gabriola Island, Canada in 1908; has not
been observed on Vancouver Island or the Canadian Gulf Islands since
1908; and was considered to be extirpated throughout its known range.
The butterfly was discovered on San Juan Island, Washington, in 1998 by
John Fleckenstein, a biologist with the Natural Heritage Program of the
Washington Department of Natural Resources (WDNR); that discovery was
published in 2001 by Guppy and Shepard (p. 160).
Taxonomy
The island marble butterfly is distinct from its nearest relative,
the large marble butterfly (Euchloe ausonides), which is widespread in
British Columbia east of the Coast Range, and in Washington and Oregon,
where it is found exclusively east of the Cascade Mountains (Guppy and
Shepard 2001, p. 160; Pyle 2002, p. 142). The large marble butterfly is
not found in coastal or island locations. Because the island marble
butterfly has distinct physical characteristics and its behavior is
adapted to the mosaic of habitat conditions and plant assemblages
specifically adapted to the San Juan Islands, the subspecies has likely
existed there for well over a century, and perhaps since the last
glaciation (R. M. Pyle, pers. comm., June 2006).
Habitat
The island marble butterfly was known to occur exclusively in
grassland habitat that historically was dominated by the grasses
Festuca roemeri (native bunchgrass), Elymus glaucus (blue wildrye),
Danthonia californica (California oat-grass), and native forbs
including Camassia quamash (common camas), Fritillaria lanceolata
(chocolate lily), Zygadenus venenosus (death camas), and Cerastium
arvense (field chickweed) (Lambert 2005c, p. 7). Arabis spp. (rockcress
species) were likely food plants for the island marble butterfly (Guppy
and Shepard 2001, p. 160); however, they are currently rare in much of
the San Juan Islands.
Island marble butterfly larvae are currently known to feed on
plants of the Brassicaceae (mustard) family in three types of habitat:
(1) Native Lepidium virginicum var. menziesii (tall or Puget Sound
peppergrass) found at the edge of coastal lagoons just above the marine
shoreline of Griffin Bay, north of American Camp, a National Historic
Park on San Juan Island (Lambert 2005c, p. 7; Miskelly 2005, p. 7); (2)
nonnative, annual mustards such as Brassica campestris (field mustard)
and Sisymbrium altissimum (tall tumble-mustard) in upland habitat; and
(3) tall tumble-mustard in sand dune habitat. Adult island marble
butterflies were most commonly observed nectaring on Lepidium
virginicum var. menziesii, Brassica campestris, Sisymbrium altissimum,
Hypochaeris radicata (hairy cat's ear), Taraxacum officinale
(dandelion), and Cakile edentula (sea rocket) (Miskelly 2005, p. 6).
The use of native and non-native mustards by the island marble
butterfly is likely a shift from the preferred larval food plants used
historically. Guppy and Shepard (2001, p. 160) discuss several species
of Arabis, Descurainia, and Barbarea (all members of the Brassicaceae
(mustard) family) that were likely used by the island marble butterfly.
Most of these plants are absent from San Juan and Lopez Islands,
possibly due to the shift in dominance to pasture grasses and other
sod-forming grasses associated with agricultural practices, which
reduce the establishment and maintenance of native forb species. The
island marble butterfly appears to have shifted its larval food
preference to the nonnative species Brassica campestris and Sisymbrium
altissimum, although the native Lepidium virginicum var. menziesii is
currently used by island marble butterfly larvae in lagoon habitat. A
similar shift to nonnative plants in situations where the preferred
larval host plants no longer exist has been observed in long-term
studies of checkerspot butterflies (Ehrlich and Hanski 2004, p. 131;
Stinson 2005, p. 88). It is not known whether this shift to using
nonnative plants by butterflies was brought on by butterfly preference
or plant availability.
Nonnative mustard species are able to colonize disturbed areas.
Many
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temporary ground-disturbing activities have short-term effects that do
not appear to result in long-term changes to island marble butterfly
population numbers or distribution. Regardless of how this shift in
host plants occurred, the use of nonnative plants such as Brassica and
Sisymbrium has likely contributed to the survival of the island marble
butterfly on grassland habitat found within San Juan County,
Washington, and is expected to continue to play a significant role in
the species' continued existence.
Surveys
In 2005 and 2006, we partnered with Washington Departments of Fish
and Wildlife and Natural Resources (WDFW and WDNR), the NPS, the
University of Washington, and the Xerces Society to survey for the
presence of the island marble butterfly during the adult flight period
and while eggs were being laid and larvae were active (early April
through late June). Qualified observers conducted approximately 325
surveys at more than 150 distinct locations in 6 counties and on 16
islands. Surveys were conducted for adult butterflies from mid-April to
mid-June; eggs and larvae were surveyed during an additional 2-week
period after the primary adult flight period (A. Potter, Wildlife
Biologist, WDFW, pers. comm. 2006; A. Lambert 2005c, p. 14; Miskelly
2006, p. 14). The survey period was initiated on April 10 in both
survey years, and was timed to commence with the flight period of the
three previous springs. Both surveys were conducted until the flight
period was finished, which was June 28, 2005, and June 17, 2006. Based
on an analysis of potential habitat using Geographic Information System
(GIS) mapping, site visits, and field verification during 2005 and
2006, we surveyed 85 to 90 percent of the potential available island
marble butterfly habitat.
All surveys were conducted using an Intuitive Controlled survey
method (Thomas and Carey 1996, p. 152), in which the surveyor walks at
a leisurely speed (about 200 meters (m) per 10 minutes), sweeping the
grasses for hidden butterflies and closely examining specific areas of
suitable habitat. A thorough search is also made in areas between
suitable habitat and at the perimeter of the habitat patch.
The ability to detect the island marble butterfly, as with most
butterflies, depends on the distribution and availability of host
plants for egg laying, larval development, and maturation to adult
stages. Island marble butterflies were found only where the host
mustards were found. Recent research by Dorazio et al. (2006, p. 842,
852) predicted that species' occurrence and butterfly diversity could
be predicted accurately through the careful location of surveys. They
concluded that a reasonable estimate of abundance would be attained
through a reduced survey effort when the plant community sampled was
selected based on the known occurrence of the target butterfly species.
Surveys conducted in 2005 focused on areas with suitable habitat,
which was defined by the presence of the three known larval food
plants, Brassica campestris, Sisymbrium altissimum, and Lepidium
virginicum var. menziesii. Sites with island marble butterfly
detections in 2005 were revisited by survey teams more than 5 times in
2006.
Our survey efforts during 2006 focused on previously unsurveyed
islands and suitable habitat patches composed of host mustards. An
additional objective in 2006 was to survey appropriate habitat adjacent
to sites on San Juan and Lopez Islands that were documented to be
occupied by island marble butterflies in 2005. The 2005 survey sites
were used as focal points, and surveys were expanded outward into
adjacent suitable habitat with landowner permission. Only a few new
subpopulations were documented in 2006.
During the 2-year survey period, 26 distinct locations occupied by
the island marble butterfly were documented. Based on these surveys and
the efforts of interested landowners, we have determined that up to
five populations may exist on the two islands. These populations are
identified as:
(1) American Camp and vicinity, which includes upland grassland
habitat, lagoon, and sand dune habitat located on southern San Juan
Island. The American Camp population is made up of lands managed by
WDNR and NPS (566 acres (ac) (229 hectares (ha)) of occupied habitat),
privately owned lands managed as rural residential that are relatively
highly developed (199 ac (81 ha) of occupied habitat), and privately
owned lands managed as rural farm and forest (66 ac (27 ha) of occupied
habitat). This population is considered the core island marble
butterfly population.
(2) The San Juan Valley subpopulation is located on privately owned
lands managed for agricultural resources (33 ac (13 ha) of occupied
habitat).
(3) The Northwest San Juan Island subpopulation is located on
privately owned lands managed as rural farm and forest (6.5 ac (3 ha)
of occupied habitat).
(4) The Central Lopez Island subpopulation is located on privately
owned lands and lands owned by the local school district managed as
rural farm and forest (241 ac (98 ha) of occupied habitat).
(5) The West Central Lopez Island subpopulation is located on
private lands managed for agricultural resources (11 ac (5 ha) of
occupied habitat).
Several other observations of dispersed or isolated individuals
were made on Lopez and San Juan Islands. Because of the relatively low
number of individuals found (compared to the sites identified above)
and the distance from the populations identified above, these isolated
individuals are not considered separate populations in the population
count. Isolated sites, outside the locations described above, comprise
an additional 2.5 ac (1 ha) of occupied habitat.
After two seasons of intensive survey effort, we concluded that
many types of habitat that we originally suspected to be potentially
suitable habitat are not being utilized because they do not provide the
conditions necessary for the larval food plants. Areas occupied by
trees, areas above approximately 300 feet (92 m) elevation, and barrens
occupied by European rabbits (Oryctolagus cuniculus) did not provide
suitable habitat conditions, and it is unlikely that they would be
occupied by island marble butterflies in the future unless the rabbits
were removed. Each of these habitat types has been surveyed and there
have been no detections of island marble butterflies.
One habitat that may be suitable, but where we did not observe
island marble butterflies, is grassland bald habitat (landforms with
shallow soils, generally on south-facing, dry, often steep slopes and
dominated by herbaceous vegetation, dwarf shrubs, or mosses and
lichens) (WDNR 2006, p. 5). This habitat is found on many of the
islands, and currently contains an assemblage of food plants used as
adult nectar sources by the island marble butterfly. More importantly,
grassland balds may be an appropriate habitat for native mustards such
as rockcress (Arabis spp.), and particularly hairy rockcress (Arabis
hirsuta), a larval food plant (Guppy and Shepard 2001, p. 158). A.
hirsuta is now uncommon on many of the San Juan County islands and was
not observed in any location where we found island marble butterflies.
Despite our current lack of documented occupation, we believe that more
study is needed before we can understand the value of grassland bald
habitat to the island marble butterfly.
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Population Size
The known population size for island marble butterflies is probably
less than 500 butterflies, and possibly as low as 300 individuals,
based on counts of adult butterflies from transect information
collected over multiple years at American Camp, the core population.
The transect counts completed at American Camp documented 270 adult
butterflies in 2004, and 194 adult butterflies in 2005. Individual
butterflies observed outside transects were added to the transect
totals to give an estimate of the number of butterflies found at all
American Camp locations, including private and public properties.
The populations found on San Juan Island appear to display classic
metapopulation dynamics where a core population exists (American Camp)
with several outlier subpopulations connected to it by migration
(Ehrlich and Hanski 2004, p. 59). The peripheral subpopulations are
made up of a few individuals that become established periodically in
suitable habitat as individuals disperse from the core, and this
habitat may or may not be occupied at all times. Peripheral locations
of island marble butterflies appear to be connected to the core by
habitat corridors that allow for dispersal and colonization.
During 2005 and 2006, when extensive searches were made to locate
new populations, we found individuals at only a few locations outside
of the core population at American Camp on San Juan Island. Most of
these locations had fewer than 5 adults, and one was composed of only a
few eggs and larvae. In 2006, new locations with individuals were
found; however, no island marble butterfly adults, eggs, or larvae were
detected at several of the outlier locations identified in 2005 (e.g.,
Lopez School and other private land holdings).
Population Structure
The core population of the Island Marble butterfly at American Camp
on San Juan Island makes up the majority of the population. It contains
as much as 75 percent of the total population, and 74 percent (832 ac
(337 ha)) of the habitat occupied by the island marble butterfly. The
remaining island marble butterflies are dispersed in subpopulations
found on private lands on San Juan Island and in two subpopulations on
Lopez Island. These peripheral subpopulations comprise approximately 20
percent of the total population. These peripheral subpopulations, along
with isolated individual areas (5 percent of the total population),
include an additional 294 ac (118 ha) of occupied habitat (26 percent
of the total occupied habitat).
All subpopulations outside of the American Camp core population are
small, and are found on mostly rural farms that are actively managed by
the landowner and have suitable habitat containing the larval food
plants. Because small-scale farming regularly disturbs the soil and
creates habitat for host plants, these farms provide suitable habitat
for the butterfly. The pattern of disturbances on public and private
properties are expected to ensure that a mosaic of larval host plants
and adult nectar sources will continue to be present within the core
area for the butterfly and at dispersed locations on the islands.
In coordination with the WDFW, the WDNR, and NPS, and with support
from Washington State University Extension Service, we held meetings
with local communities on San Juan and Lopez Islands in March 2006.
More than 50 people attended these workshops, during which the biology
of the island marble butterfly and conservation actions that could be
implemented to promote suitable habitat were discussed. These meetings
provided opportunities for surveying additional areas and provided
habitat enhancement guidance for those landowners wanting to share in
the conservation of the butterfly.
Summary of Factors Affecting the Species
Section 4 of the Act (16 U.S.C. 1533), and implementing regulations
at 50 CFR part 424, set forth procedures for adding species to the
Federal Lists of Endangered and Threatened Wildlife and Plants. Under
section 4(a) of the Act, we may list a species on the basis of any of
five factors, as follows: (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 finding, information
regarding the status of, and threats to, the island marble butterfly in
relation to the five factors provided in section 4(a)(1) of the Act
follows.
A. The Present or Threatened Destruction, Modification, or Curtailment
of Its Habitat or Range
Residential development, road construction and decommissioning,
road maintenance activities, the use of herbicides, prescribed fire,
and European rabbits may impact the island marble butterfly in its
current range on San Juan and Lopez Islands of San Juan County,
Washington.
Development
Residential development occurs on both San Juan and Lopez Islands.
In particular, the Cattle Point Estate and Eagle Cove developments on
private lands adjacent to NPS lands at American Camp threaten Island
Marble butterfly habitat and increase mortality by increasing roads and
traffic. These residential areas contain approximately 199 ac (81 ha)
of the habitat occupied by island marble butterfly, constituting 18
percent of the total estimated occupied habitat. Approximately 50
percent of the habitat at American Camp proper (566 ac (229 ha)),
including the NPS and WDNR lands will be managed in a natural
condition, which is compatible with the conservation of the island
marble butterfly.
Development is occurring less rapidly to the north and west of
American Camp and on Lopez Island, where small, rural farms with
pastures and low-density private residences exist. Current management
in these areas is compatible with management of the island marble
butterfly habitat. These areas contain about 361 ac (146 ha),
constituting 32 percent of habitat known to be occupied by island
marble butterflies.
Road Construction
A planned road relocation project by the Federal Highway
Administration (FHA) will result in short-term adverse affects to the
island marble butterfly. This project is planned for Cattle Point Road,
the single access to American Camp, the Cattle Point Estates (a
residential area east of American Camp), and a WDNR parcel known as the
Cattle Point Natural Resource Conservation Area. The existing road,
which covers about 3 ac (1 ha) is eroding. The slumping (deep-seated
rotational failure) of the sandy soil is displacing the high bluff
directly below the current road grade.
Impacts of the road relocation could include temporary loss of as
much as 13 ac (5 ha) of island marble butterfly habitat due to road
construction activities and clearing, and removal of the subspecies'
larval food plants and adult nectar sources. Approximately 3 ac (1 ha)
of habitat could be lost in the short term, if the preferred
alternative is implemented. The NPS is planning to restore the
decommissioned area using native grasses and forbs (P. Dederich, NPS
Superintendent, pers. comm. 2006;
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NPS Pacific West Region Directive 063), and as a result there would be
no net loss of habitat from the road relocation over the long term.
Consistent with their resource management policy, the NPS will
require the use of native grasses and forbs for restoration of any
disturbed areas (NPS Management Policy 1988, Section 4.4.1.2). The
nonnative field mustard and tumble-mustard, which are primary larval
host plants and adult nectar plants of the island marble butterfly in
upland habitat, will likely become established on the disturbed ground
because their plentiful seed will germinate the first year after ground
disturbance (mustards are generally annual species with high seed
production).
Construction of the road will require the completion of an
Environmental Impact Statement (EIS) under the National Environmental
Policy Act (42 U.S.C. 4321 et seq.), and funding from the FHA. No
schedule for the EIS or expected funding was available at the time this
notice was written. However, based on information from the FHA, a draft
EIS is expected by 2007. There appears to be no island marble butterfly
breeding habitat along the proposed route for the Cattle Point highway
realignment in the Park (Pyle 2006). While some individuals and host
plants may occur, the road-building planning process and construction
may proceed with little likelihood of mortality to these butterflies.
Road Maintenance Activities
Adults, eggs, and larvae of the island marble butterfly were
observed in 2005, at the Fisherman's Bay tombolo (a narrow beach
landform that connects the mainland to an island) on Lopez Island. In
July 2005, the habitat was buried by sand by the road maintenance crews
to make the vegetation less flammable for a July 4th fireworks display,
likely killing any larvae or eggs that may have been present. When the
larval food plants subsequently resprouted, they were mowed during
routine road maintenance, likely removing habitat for eggs and larval
development in 2006. This site was visited four times in 2005, and six
times in 2006, and no adult butterflies, eggs, or larvae were observed.
After discussions with San Juan County highway officials at the March
2006 workshop, and again in June 2006, the County agreed to address our
concerns regarding their road maintenance activities and management of
habitat for the island marble butterfly (Ruth Milner, WDFW, in litt.
2006)
Grassland Restoration
Grassland restoration activities being implemented by NPS to
restore historic grassland conditions in San Juan Islands National
Historical Park (SJINHP) have improved habitat for island marble
butterflies. Nonnative vegetation targeted for removal includes pasture
grasses and woody shrubs. In 2005, NPS implemented grassland
restoration activities that included the planting of native species and
the removal of invasive vegetation through the application of
herbicides and prescribed fire. Based on these activities, especially
the successful combination of herbicide and prescribed fire at American
Camp, we anticipate that long-term positive effects of habitat
restoration will significantly outweigh short-term impacts. A more
robust island marble butterfly population is expected as a result of
restoration activities due to an increase in the establishment of
larval food plants and native nectar sources, and a reduction in
competing weedy forb vegetation and encroaching woody shrubs and trees.
The results of the restoration efforts implemented in 2005 at American
Camp have produced high quality habitat for the island marble
butterfly, increasing by approximately four times the number of host
plants in the restoration area.
Herbicides have been used in small experimental applications to
test methods for reducing the distribution and spread of nonnative
grasses at American Camp. In July 2005, herbicides were applied to
approximately 3.7 ac (1.5 ha) of the 600 ac (243 ha) of grassland
habitat at American Camp (William Gleason, Chief, Resource Management,
SJINHP, pers. comm. 2005). Herbicide treatment was followed by a
prescribed fire on the same footprint of land. Because these activities
occurred prior to the end of the flight period, they likely harmed
eggs, larvae, and adult island marble butterflies that were utilizing
the food plants and grassland ecosystem. While many of the plants
occupied by larvae were removed from the site prior to the herbicide
treatment by volunteers and NPS personnel and relocated elsewhere
(Lambert 2005b, p. 11), some may have been missed because of the
difficulty in locating larvae.
The herbicide and prescribed fire treatments were conducted in a
test area as preparation for a larger scale restoration project that
NPS plans for restoring the native grassland plant community at
American Camp. Disturbances produced by the herbicides and fire
treatments also create suitable areas for the establishment of
mustards. Based on discussions with us and other interested parties,
NPS has agreed to implement restoration activities at a time outside of
the flight period of the island marble butterfly. In 2006, a year after
the experimental treatment, the grassland area was recovering and
providing significantly higher-quality habitat for the island marble
butterfly than was present prior to the management action. More than
480 tumble-mustard plants were counted in May 2006, and nearly 20
percent (91 plants) of the plants had island marble butterfly eggs or
larvae attached. This is approximately four times the number of mustard
plants found previously at this same location (T. Thomas, pers.
observation, 2006).
Grassland restoration activities can have short-term detrimental
effects to the island marble butterfly; however, they appear
insignificant when compared to the long-term benefits.
European Rabbits
The European rabbit is a nonnative, burrowing species common on San
Juan Island, and at American Camp in San Juan Island National
Historical Park. Hall (1977, p. 293) summarized the history of the
European rabbit on San Juan Island. Currently, more than 1,000 rabbits
(Agee and West 2002, p. 3) consume all vegetation within approximately
180 ac (73 ha) of formerly grassland habitat at American Camp. However,
the rabbit population does not appear to be expanding, and planning is
underway by NPS to reduce its population size over time.
Summary of Factor A
The core of the population at American Camp is protected from
development. Road construction and maintenance activities are not
considered to be current threats to the island marble butterfly or its
habitat. Grassland restoration activities (including herbicide
treatments and prescribed fire) have shown success in increasing
habitat and host plants and European rabbits do not appear to be a
threat to the subspecies. Thus, we have determined that the present or
threatened destruction, modification, or curtailment of the island
marbled butterfly's habitat or range do not constitute a threat to the
subspecies such that listing under the Act is warranted.
B. Overutilization for Commercial, Recreational, Scientific, or
Educational Purposes
The NPS has not observed butterfly collecting at American Camp, or
other locations where the island marble
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butterfly is present. Under NPS regulations, the collection of living
or dead wildlife, fish, or plants, or the parts or products thereof, is
prohibited on lands under NPS jurisdiction without a permit (36CFR
2.1(a)(1)(i) and (a)(1)(ii)). A verbal request was made by one
individual for permission to collect this species (Rolfs, pers. comm.
2004). After discussions with conservation partners, the individual
agreed to withdraw his request. Given the small number of island marble
butterflies that remain in the wild, any collection of butterflies is
likely to increase its extinction risk. However, at this time we do not
believe that overutilization for commercial, recreational, scientific,
or educational purposes is a significant threat to the island marble
butterfly such that listing under the Act is warranted.
C. Disease or Predation
While predation by paper wasps (members of the Ichneumonidae,
Vespidae, and Thomisidae families) and by crab spiders (Diaea spp.) has
been documented for the island marble butterfly (A. Lambert, NPS
Science Day Conference, June 23, 2006), neither is considered to be a
significant threat to the subspecies.
D. The Inadequacy of Existing Regulatory Mechanisms
As mentioned previously in this finding, under NPS regulations, the
collection of living or dead wildlife, fish, or plants, or the parts or
products thereof, is prohibited on lands under NPS jurisdiction without
a permit (36 CFR 2.1(a)(1)(i) and (a)(1)(ii)).
Washington State has designated the island marble butterfly as a
candidate species, and identified the species as critically imperiled
in its Comprehensive Wildlife Conservation Strategy (WDFW 2005, pp.
219, 314, 336-337). In this strategy, the WDFW identified several
specific conservation actions for island marble butterfly management,
including continuing to search for new populations and monitoring known
sites, and protecting and restoring island marble butterfly habitat.
Under San Juan County's Critical Area Ordinance, or San Juan County
Code (SJCC 18.30.160.B2.c and SJCC 18.30.160.D.b.iv.), the County
defers to State guidance for management recommendations for any State-
designated priority habitat or species. However, the comprehensive plan
for San Juan County requires concentration of development in specific
areas and maintains a rural farm landscape elsewhere on the islands.
This has been relatively successful in concentrating the high-density
development outside of island marble butterfly population areas, and
maintaining suitable habitat on Lopez and San Juan Islands.
Based on the aforementioned regulatory protections, we have
determined that the inadequacy of existing regulatory mechanisms does
not constitute a threat to the island marble butterfly such that
listing under the Act is warranted.
E. Other Natural or Manmade Factors Affecting Its Continued Existence
Natural threats to the island marble butterfly include the browsing
of larval food plants by deer, and impacts of storm tides and tidal
surges. Recreational trail use was identified in the petition as a
threat; however, there is no evidence that this activity affects island
marble butterflies.
Black-tailed deer (Odocoileus columbianus) browse on larval food
plants and adult nectar plants at most locations occupied by island
marble butterflies (Miskelly 2005, p. 16), but the browsing does not
appear to be at a level that significantly affects the butterflies.
On February 4, 2006, a storm event with high tides and strong,
gusty winds from the north created tidal surges in Griffin Bay, and the
coastal lagoon habitat of the island marble butterfly was inundated
with water. Logs that had been cast ashore in previous storms, and that
provided anchors and structure for the establishment of vegetation,
were floated and displaced, and coarse sediments were deposited on the
beach, burying food plants and winter pupation sites for the island
marble butterfly. Approximately 5 percent of the habitat available to
the subspecies was buried, killing any pupae that were present. During
the spring of 2006, several adult island marble butterflies were
observed in this area (A. Lambert, pers. comm. 2006). Although the new
substrate, deposited in February 2006, has become populated by a high
density of Puget Sound peppergrass (R.M. Pyle, pers. comm. 2006), no
butterfly reproduction was documented in the lagoon habitat during
2006, possibly due to the timing of the revegetation, which occurred
after the flight period of the island marble butterfly. The tidal surge
was measured as a typical 5- to 10-year event based on a 100-year
record; however, the combination of tidal surge and wind gusts greater
than 34 mph (54 km/h) created beach-altering conditions that were
relatively uncommon. We expect that this site will be colonized by
island marble butterflies in 2007.
The natural factors listed above likely do not significantly impact
the island marble butterfly population. Therefore, we have determined
that there are no other natural or manmade factors that threatened the
island marble butterfly such that its listing under the Act is
warranted.
Finding
We assessed the best scientific and commercial information
available regarding the threats faced by the island marble butterfly.
We have reviewed the petition, information available in our files, and
information submitted to us during the public comment period following
our 90-day petition finding (71 FR 7497; February 13, 2006). We also
consulted with recognized butterfly experts, Federal and State resource
agencies, and non-governmental organizations with butterfly expertise,
and we collected additional survey data.
Actions that may impact island marble butterflies include
development for housing, road construction, road maintenance,
collisions with vehicles, storm and tidal surges that inundate and bury
habitat, herbivory of host plants by deer, loss of habitat to nonnative
rabbits, and succession of grassland habitat to shrubs and trees.
However, most, if not all, of these impacts are localized. Due to the
island marble butterfly's reliance on nonnative mustard species that
experience resurgence after ground-disturbing activities, many
temporary ground-disturbing activities have short-term effects that do
not appear to result in negative long-term impacts to population
numbers or distribution.
While the island marble butterfly population has likely always been
low (having not been observed prior to 1998), the subspecies has
evidently been present on San Juan Island, and possibly Lopez Island,
for the past century. This persistence has occurred without deliberate
management meant to sustain the butterfly. This suggests that the
butterfly has managed to either persist as several small populations or
as one core population in the American Camp area for many years, with
individual butterflies migrating and establishing satellite populations
elsewhere on San Juan Island and on Lopez Island.
Long-term threats are limited to less than 18 percent of the
occupied area. The remaining 82 percent of the area occupied by the
island marble butterfly is subject to short-term impacts that typically
result in increased habitat of non-native mustards through ground
disturbance, and increased use by island marble butterflies. This
pattern of periodic disturbances is generally
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compatible with sustaining the subspecies in the longterm.
The current threats analysis supports a determination that listing
the island marble butterfly under the Act is not warranted. We will
continue to assess the status of the butterfly by working with NPS,
WDFW, conservation organizations, faculty and students from the
University of Washington, the Washington State University Extension
Service, and all private landowners with an interest in contributing to
the conservation of this species. In addition, we will continue to work
with the NPS on implementation of the Conservation Agreement for the
butterfly. Although we did not rely on efforts identified in this new
agreement as a basis for our determination, we anticipate that these
efforts will enhance the conservation of the subspecies.
Based on an analysis of the current status and threats to the
subspecies, we find that listing the island marble butterfly under the
Act is not warranted. We request that you submit any new information
concerning the status of or threats to this species to our Western
Washington Fish and Wildlife Office (see ADDRESSES section) whenever it
becomes available. New information will help us monitor the species and
encourage its conservation. If an emergency situation develops for this
or any other candidate species or species of concern, we will act to
provide immediate protection.
References Cited
A complete list of all references cited herein, as well as others,
is available upon request from the Western Washington Fish and Wildlife
Office (see ADDRESSES section).
Author
The primary author of this document is Ted Thomas, U.S. Fish and
Wildlife Service, Western Washington Fish and Wildlife Office (see
ADDRESSES section).
Authority
The authority for this action is the Endangered Species Act of
1973, as amended (16 U.S.C. 1531 et seq.).
Dated: November 3, 2006.
Marshall P. Jones, Jr.,
Acting Director, Fish and Wildlife Service.
[FR Doc. E6-19064 Filed 11-13-06; 8:45 am]
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