Sonora skipper (Polites sonora) COSEWIC assessment and status report: chapter 2
COSEWIC Executive Summary
Sonora Skipper
Polites sonora
Species information
The Sonora Skipper is a butterfly of the skipper family Hesperiidae. Adults have a wingspan of 25 to 30 mm. The upper side of the wings is a combination of rusty orange and brown with blackish wing borders. The under side of the forewings has a basal black patch, tawny and pale areas in the median area, and a dark brown border. The ventral surface of the hindwings is ochre brown with a distinct semicircular band of pale spots. Canadian specimens do not fit the description of any named subspecies, but only one entity exists in Canada and the entire entity is the subject of this status report.
Distribution
The species is widely distributed in western North America, from extreme southwestern British Columbia south to Baja California and east in the United States to Wyoming and Colorado. The known Canadian distribution is limited to the Cascade Mountains and adjacent Thompson Plateau, south of Princeton, British Columbia. There are some old records of the species from sites that have not been verified recently and some recent records from six Canadian locations, as well as one unconfirmed record.
Habitat
Known habitats for the Sonora Skipper are moist grassland openings in mountainside forests, logged areas and an agricultural clearing in a valley bottom.
Biology
Very little is known about the biology of the Sonora Skipper in Canada or elsewhere. It has been reared successfully in the laboratory on several grass species, but the larval food plants used in nature are unknown. Adults have been found from 21 June to 13 August.
Population sizes and trends
The sizes and trends of individual Canadian populations of the Sonora Skipper are unknown. Only small numbers of adults have been observed in Canada.
Limiting factors and threats
The most likely limiting factor for the Sonora Skipper is the availability of moist grassy habitat without tree cover in an area where coniferous forests predominate. Intensive grazing, forest ingress into meadows, and fire may have a negative impact on populations. Logging has increased habitat supply in one location, but future plantation growth will render the habitat unusable if grassy openings are not maintained.
Special significance of the species
The Sonora Skipper is one of several butterfly species that have a primarily southern distribution in North America and reach their northern range limits in extreme southern British Columbia. The Canadian population is part of an apparently disjunct population group that occurs only in the north Cascade Mountains near the border between British Columbia and Washington, with six of the eleven (55%) known locations of the group occurring in Canada.
Existing protection
If the Sonora Skipper is still extant in Manning and Cathedral Provincial Parks, it is protected under provincial legislation. There is no specific legislation that protects this species in Canada.
COSEWIC History
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 5th2003, 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.
COSEWIC Mandate
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 (2006)
- Wildlife Species
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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)
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A wildlife species that no longer exists.
- Extirpated (XT)
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A wildlife species no longer existing in the wild in Canada, but occurring elsewhere.
- Endangered (E)
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A wildlife species facing imminent extirpation or extinction.
- Threatened (T)
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A wildlife species likely to become endangered if limiting factors are not reversed.
- Special Concern (SC)*
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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)**
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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.