COSEWIC Status Appraisal Summary on the Island Marble Euchloe ausonides insulanus in Canada – 2010

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Document Information

Document Information

Extirpated – 2010

COSEWIC status appraisal summaries are working documents used in assigning the status of wildlife species suspected of being at risk in Canada. This report may be cited as follows:

COSEWIC. 2010. COSEWIC status appraisal summary on the Island Marble Euchloe ausonides insulanus in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. viii pp.

Production note:
This status appraisal summary constitutes a review of classification of the Island Marble Euchloe ausonides insulanus in Canada which was last assessed by COSEWIC in 2000. The 2000 COSEWIC Status Report on the Island Marble Euchloe ausonides insulanus in Canada is posted on the Species at Risk Public Registry link.

COSEWIC would like to acknowledge James Miskelly for writing the status appraisal summary on the Island Marble Euchloe ausonides insulanus in Canada, prepared under contract with Environment Canada. This status appraisal summary was overseen and edited by Laurence Packer, Co–chair of the Arthropods Specialist Subcommittee.

For additional copies contact:

COSEWIC Secretariat
c/o Canadian Wildlife Service
Environment Canada
Ottawa, ON
K1A 0H3

Tel.: 819–953–3215
Fax: 819–994–3684

Également disponible en français sous le titre Sommaire du statut de l’espèce du COSEPAC sur le Marbré insulaire (Euchloe ausonides insulanus) au Canada.

© Her Majesty the Queen in Right of Canada, 2010.
Catalogue No. CW69–14/2–3–2010E–PDF
ISBN 978–1–100–16630–8

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COSEWIC Assessment Summary

Assessment Summary – April 2009

Common name
Island Marble

Scientific name
Euchloe ausonides insulanus


Reason for designation
* A reason for designation is not specified when a review of classification is conducted by means of a status appraisal summary.

British Columbia

Status history
Extirpated by 1910. Designated Extirpated in April 1999. Status re–examined and confirmed in May 2000 and in April 2010.

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COSEWIC Status Appraisal Summary

Euchloe ausonides insulanus
Island Marble - Marbré insulaire

Jurisdictions: BC

Current COSEWIC Assessment:

Status category:

XT = Extirpated

Date of last assessment: May 2000

Reason for designation at last assessment: This butterfly was formerly found on two islands off the west coast, but disappeared from both sites by 1910 because of loss of the larval host plant. It has not been seen in Canada since that time.

Criteria applied at last assessment: N/A

If earlier version of criteria was applied1, provide correspondence to current criteria: N/A.

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Recommendation: Update to the status report NOT required (species’ status category remains unchanged)

sufficient information to conclude there has been no change in status category.

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Evidence (indicate as applicable):

Wildlife species:

Change in eligibility, taxonomy or designatable units: no


No additional data since previous assessment.



Change in Extent of Occurrence (EO): no

Change in Area of Occupancy (AO): no

Change in number of known or inferred current locations: no

Significant new survey information: yes


Considerable effort has been devoted to butterfly surveys in the historic range of the Island Marble in Canada since 2001.  Southeastern Vancouver Island and the Gulf Islands have been surveyed extensively in a series of projects aimed at threatened and endangered butterflies.  The British Columbia Ministry of Environment and Environment Canada have been the major proponents of these projects and the principal investigators have been Crispin Guppy, Nick Page, James Miskelly, and Jamie Fenneman.  At least 500 person hours have been spent conducting professional surveys in the historic range of the Island Marble during the period of the year that the species is detectable.  In additional, butterfly enthusiasts on southern Vancouver Island have volunteered at least 2000 person hours conducting surveys in the historic range of the Island Marble since 2001 (Victoria Natural History Society 2001–2008).  The Island Marble has not been detected in these surveys.


Population Information:

Change in number of mature individuals: no

Change in total population trend: no

Change in severity of population fragmentation: no

Change in trend in area and/or quality of habitat: no

Significant new survey information: no


There are no known Canadian populations.



Change in nature and/or severity of threats: no


No additional data since previous assessment.



Change in effective protection: no


No additional data since previous assessment.


Rescue Effect:

Evidence of rescue effect: no


The closest populations to Canada are small, declining, and located at least 15 km away across Haro Strait (Miskelly and Potter 2008). There is no evidence that the species can cross such a wide expanse of unsuitable habitat. Other subspecies of Euchloe ausonides disperse an average of less than 200 m per day (Scott 1975a). The greatest recorded dispersal distance is 3 km (Scott 1975b).


Quantitative Analysis:

Change in estimated probability of extirpation: no


The species is already extirpated.


Summary and Additional Considerations:

Recent studies of the Island Marble in San Juan County, Washington, where the butterfly still persists, have provided much new information about it habitats and ecology.  Contrary to previous reports (Shepard 2000, Guppy and Shepard 2001, Parks Canada Agency 2006), there is no evidence that it has ever been found in Garry Oak woodland or has ever been associated with rockcress (Arabis sp.) as a larval host plant (Miskelly and Potter 2005, Miskelly and Fleckenstein 2006, Miskelly and Potter 2008).  Extant populations of Island Marble are found in old fields, along eroding shorelines, in disturbed native grassland, and around tidal lagoons.  Larval host plants are field mustard (Brassica campestris), tall tumble mustard (Sisymbrium altissimum) and tall pepper–grass (Lepidium virginicum).  Only the latter is a native species. 

The historic Canadian range of the Island Marble has been extensively surveyed since 2001 in an effort to locate it along with other at risk butterflies.  These surveys have targeted a variety of habitats, including the habitats used by the Island Marble in its extant American range.  During these surveys, neither the Island Marble nor apparently suitable habitat has been detected.  All available evidence suggests that the Island Marble is extirpated in Canada.

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List of reviewers:

The Status Appraisal Summary was sent to the following jurisdictions for review:

  • Canadian Wildlife Service
  • Parks Canada Agency
  • Province of British Columbia (Dave Fraser)
  • Members of the COSEWIC Arthropods Species Specialist Subcommittee
  • Members of the Aboriginal Traditional Knowledge Subcommittee (Donna Hurlburt and Dan Benoit)

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Heron, Jennifer.  Chair, British Columbia Invertebrates at Risk Recovery Team. Invertebrate specialist, BC Ministry of Environment. Vancouver, BC.

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Sources of information:

Guppy, C.S. and J.H. Shepard. 2001. The butterflies of British Columbia. Royal BC Museum and UBC Press, Victoria and Vancouver, BC.

Miskelly, J. and J. Fleckenstein.  2006.  Surveys for Island Marble butterfly (Euchloe ausonides insulanus) in San Juan County, Washington, 2006.  Natural Heritage Report 2007–01. Washington Department of Natural Resources, Olympia, WA.

Miskelly, J. and A. Potter. 2005.  2005 surveys for Island Marble Butterfly (Euchloe ausonides insulanus) in northern coastal Washington.  Report to Washington Department of Fish and Wildlife, Olympia, WA.

Miskelly, J. and A. Potter. 2008.  Surveys for Island Marble butterfly (Euchloe ausonides insulanus) in San Juan County, Washington, 2007.  Report to Washington Department of Fish and Wildlife, Olympia, WA.

Parks Canada Agency. 2006. Recovery Strategy for Multi–species at Risk in Maritime Meadows Associated with Garry Oak Ecosystems in Canada. In Species at Risk Act Recovery Strategy Series. Parks Canada Agency, Ottawa, ON.

Scott, J.A. 1975a. Movements of Euchloe ausonides (Pieridae). Journal of the Lepidopterists’ Society 29(1): 24–31.

Scott, J.A. 1975b. Flight Patterns among eleven species of diurnal lepidoptera. Ecology 56: 1367–1377.

Shepard, J.H. 2000. Status Report on the Island Marble, an Undescribed Subspecies of Euchloe ausonides (Lucas) (Lepidoptera: Pieridae) in British Columbia. Committee on the Status of Wildlife in Canada, Ottawa, ON.

Victoria Natural History Society. 2001–2008. Unpublished data associated with Victoria Butterfly Counts. Victoria, BC.


The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) was created in 1977 as a result of a recommendation at the Federal–Provincial Wildlife Conference held in 1976. It arose from the need for a single, official, scientifically sound, national listing of wildlife species at risk. In 1978, COSEWIC designated its first species and produced its first list of Canadian species at risk. Species designated at meetings of the full committee are added to the list. On June 5, 2003, the Species at Risk Act (SARA) was proclaimed. SARA establishes COSEWIC as an advisory body ensuring that species will continue to be assessed under a rigorous and independent scientific process.


The Committee on the Status of Endangered Wildlife in Canada (COSEWIC) assesses the national status of wild species, subspecies, varieties, or other designatable units that are considered to be at risk in Canada. Designations are made on native species for the following taxonomic groups: mammals, birds, reptiles, amphibians, fishes, arthropods, molluscs, vascular plants, mosses, and lichens.

COSEWIC Membership

COSEWIC comprises members from each provincial and territorial government wildlife agency, four federal entities (Canadian Wildlife Service, Parks Canada Agency, Department of Fisheries and Oceans, and the Federal Biodiversity Information Partnership, chaired by the Canadian Museum of Nature), three non–government science members and the co–chairs of the species specialist subcommittees and the Aboriginal Traditional Knowledge subcommittee. The Committee meets to consider status reports on candidate species.

Definitions (2010)

Wildlife Species
A species, subspecies, variety, or geographically or genetically distinct population of animal, plant or other organism, other than a bacterium or virus, that is wild by nature and is either native to Canada or has extended its range into Canada without human intervention and has been present in Canada for at least 50 years.

Extinct (X)
A wildlife species that no longer exists.

Extirpated (XT)
A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.

Endangered (E)
A wildlife species facing imminent extirpation or extinction.

Threatened (T)
A wildlife species likely to become endangered if limiting factors are not reversed.

Special Concern (SC)*
A wildlife species that may become a threatened or an endangered species because of a combination of biological characteristics and identified threats.

Not at Risk (NAR)**
A wildlife species that has been evaluated and found to be not at risk of extinction given the current circumstances.

Data Deficient (DD)***
A category that applies when the available information is insufficient (a) to resolve a species’ eligibility for assessment or (b) to permit an assessment of the species’ risk of extinction.

* Formerly described as “Vulnerable” from 1990 to 1999, or “Rare” prior to 1990.
**  Formerly described as “Not In Any Category”, or “No Designation Required.”
***  Formerly described as “Indeterminate” from 1994 to 1999 or “ISIBD” (insufficient scientific information on which to base a designation) prior to 1994. Definition of the (DD) category revised in 2006.

The Canadian Wildlife Service, Environment Canada, provides full administrative and financial support to the COSEWIC Secretariat.

1 An earlier version of the quantitative criteria was used by COSEWIC from October 1999 to May 2001 and is available on the COSEWIC website.