Half-moon hairstreak (Satyrium semiluna) COSEWIC assessment and status report: chapter 13
Technical summary
Half-moon Hairstreak
Porte-queue demi-lune
Range of occurrence in Canada: British Columbia (BC) and Alberta (AB)
Extent and area information
Population information
unlikely in BC population
Anarchist Mtn. - unknown
Keremeos Columns - unknown
Kilpoola grasslands - unknownMt. Kobau - unknown
Richter Pass - unknown
White Lake - unknown
Threats
- Intensive livestock grazing
- Loss of habitat to agriculture, infrastructure development and other uses
- One location could be affected by expansion of an aggregate pit
- Habitat change by invading knapweed
- Habitat change and direct mortality from knapweed control activity
Rescue effect: Moderate
Quantitative Analysis
Not applicable
Current status
Committee on the Status of Endangered Wildlife in Canada (COSEWIC): Endangered (2006)
NatureServe: G4, N1N2 in Canada, S1 in BC, SH (should be updated to S1?) in AB, S4 in Washington and Montana, and SNR in Idaho.
General Status: may be at risk
Status and reasons for designation
Reasons for Designation: The butterfly occurs as disjunct populations in two small, restricted areas at the northern extreme of the species’ range. The species’ population has likely declined in the past as a result of habitat loss. Both populations continue to be threatened by habitat loss and degradation. In British Columbia the species occurs in an area under severe pressure for development. In both Alberta and British Columbia, invasive weeds also pose a serious threat.
Applicability of criteria
Criterion A (Declining Total Population): no data.
Criterion B (Small Distribution, and Decline or Fluctuation):
- the extent of occurrence is smaller than 5000 km2 (485 km2) – 1
- the area of occupancy is smaller than 500 km2 (smaller than 250 km2) – 2
- the population is severely fragmented – a
- and there are continuing declines in the quality of the habitat – b(iii)
- resulting in inferred declines in the number of mature individuals – b(v)
Criterion C (Small Total Population Size and Decline): Likely meets Threatened C2a(i):
- the number of mature individuals is fewer than 10 000
- there are no data on decline rates
- but continuing decline in population size are inferred on the basis of habitat loss and degradation – 2
- with a population structure – a
- where it is likely that in low population years, the situation exists where no population contains more than 1000 mature individuals – i
- and although the Alberta population undergoes extreme fluctuations in number of mature individuals, there is no evidence to support extreme fluctuations in the overall population.
Criterion D (Very Small Population or Restricted Distribution): Not applicable.
Criterion E (Quantitative Analysis): No data.
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