[Federal Register: November 14, 2006 (Volume 71, Number 219)]
[Proposed Rules]               
[Page 66292-66298]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]



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.


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, 

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 



    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

[[Page 66293]]

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).


    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).


    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. 

[[Page 66294]]

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.


    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 
    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 
    (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.

[[Page 66295]]

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 

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, 
    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 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 
    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. 
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 


    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).


    The primary author of this document is Ted Thomas, U.S. Fish and 
Wildlife Service, Western Washington Fish and Wildlife Office (see 
ADDRESSES section).


    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]