SANBI

Rationale (Changed due to Same category and criteria)

This taxon is a highly range-restricted endemic to the Western Cape Province, South Africa (EOO 0.006 km2, AOO 4 km2). There is only one location, and there is continuing decline in the quality of the habitat (amount of host plant) and the number of mature individuals because of a severe drought, and more recently, a devastating fire. There are also extreme fluctuations in the number of mature individuals. There are less than 250 mature individuals, and continuing decline of >25% over three years. All of the mature individuals are in one subpopulation. The taxon thus qualifies as Critically Endangered under criteria B and C.

Distribution

Endemic to the Western Cape Province, confined to the Brenton Blue Butterfly Reserve near Knysna. Now extinct at the only other known locality at Nature's Valley.

Decline

Deterioration of quality of habitat occurs over time due to lack of megaherbivore and fire disturbances. Active management of the habitat is necessary to simulate such disturbances and maintain the habitat in suitable condition.

Habitat View more ecological information

Population trend

Trend

A complete population analysis is described in Chapter 5 - Population Dynamics of Orachrysops niobe (Edge, 2005). The current adult population is < 50, having declined from c. 150 in 2008. This is mostly the result of prolonged drought conditions in the southern Cape.

Threats

There is no direct evidence of how the Brenton Blue population at Nature's Valley became extinct, but it can be inferred that this came about because houses were built on the primary dunes where the butterfly was breeding, which had a good sea view, reducing the amount of available habitat by over 90%. This was compounded by the exclusion of fire from the dune fynbos (to protect the houses). The small residual subpopulation of butterflies was thus unable to persist. All foreseeable threats to the single remaining subpopulation are being managed at this species' one remaining locality at the Brenton Blue Nature Reserve. The most significant future potential threats to this site are: 1) Unforeseeable stochastic events such as a runaway fire occurring at a time in the life cycle (mid-November or mid-March) when most adult individuals would be killed, or a very hot fire at other times which could kill all the larvae and pupae underground. The Knysna fire of June 2017 may have been such an event and the survival of the species is in the balance. 2) A prolonged drought, which could cause most of the host plants to die back and drastically reduce the food resource available to the larvae, is another potential threat. The serous decline in numbers of adults during the 2014 - 2017 drought demonstrated the severity of this threat. 3) A loss of genetic diversity in the small isolated population is possible. There is no scientific evidence to substantiate this, because the adult population is too small to sustain even a minimal amount of DNA sampling. 4) Future failure to manage the Special Nature Reserve adequately beyond the lifetime of the current Brenton Blue Trustees is a threat. 5) The longer term impact of global warming could be a significant future threat, particularly because of the reliance of this butterfly and its plant and ant associates on a cool microclimate.

Conservation

The Brenton Blue Butterfly Reserve is managed by a management committee established by the Brenton Blue Trust, with representatives from all stakeholders, including the conservation agency CapeNature. A management plan at this site has been established and is continuously refined by research, and continuous monitoring of the habitat and population levels is undertaken during the flight periods. Expansion of the reserve to 15 ha has been approved by the Knysna Municipality. This is a medium-term project, and habitat alteration to make it suitable for the host plant has commenced. Attempts to reintroduce the butterfly at the Natures Valley fynbos reserve (about 60 km to the east), where it originally occurred and where habitat restoration work had been undertaken, have not met with success so far because of the poor condition of the host plant population, the small area of suitable habitat, and the absence of the host ant Camponotus baynei. Following a devastating fire at Brenton in June 2017 a new research program has been established to monitor the recovery of the ecosystem and to determine whether the butterflies have survived.

References

[@book{772,
 address = {Johannesburg &Cape Town},
 author = {Mecenero, S., Ball, J.B., Edge, D.A., Hamer, M.L., Henning, G.A., Krüger, M., Pringle, E.L., Terblanche, R.F. & Williams, M.C. (eds)},
 publisher = {Saftronics (pty) Ltd and  Animal Demography Unit, University of Cape Town},
 title = {Conservation assessment of butterflies of South Africa, Lesotho and Swaziland: Red List and Atlas.},
 year = {2013}
}
,@book{772,
 address = {Pretoria},
 author = {Henning, G.A., Terblanche, R.F. & Ball, J.B. (eds)},
 publisher = {South African National Biodiversity Institute},
 title = {South African Red Data Book: butterflies. SANBI Biodiversity Series},
 year = {2009}
}
,@article{772,
 author = {SANBI},
 journal = {South African National Biodiversity Institute},
 pages = {0},
 title = { Vegetation Map of South Africa, Lesotho and Swaziland [vector geospatial dataset] 2012. Available from the Biodiversity GIS website.},
 volume = {0},
 year = {2012}
}
,@book{882,
 address = {Cape Town, South Africa},
 author = {Woodhall, S.E.},
 publisher = {Struik},
 title = {Field Guide to Butterflies of South Africa.},
 year = {2005}
}
,@book{890,
 address = {Pretoria},
 author = {Henning, S.F. & Henning, G.A.},
 publisher = {Council for Scientific and Industrial Research},
 title = {South Africa Red Data Book - Butterflies.},
 year = {1989}
}
,@book{893,
 author = {Williams, M.C.},
 publisher = {CD-ROM. Available from the author at mark.williams[at]up.ac.za.},
 title = {Butterflies and skippers of the Afrotropical Region.},
 year = {2016}
}
,@article{895,
 author = {Edge, D.A.},
 journal = {Metamorphosis},
 number = {2.0},
 pages = {28--46},
 title = {Butterfly conservation in the southern Cape, South Africa.},
 volume = {16},
 year = {2005}
}
,@article{15414,
 author = {Edge, D.A. & van Hamburg, H.},
 journal = {Journal of Research on the Lepidoptera},
 pages = {21--33},
 title = {Larval feeding behaviour and myrmecophily of the Brenton Blue, <i>Orachrysops niobe</i> (Trimen) (Lepidoptera: Lycaenidae).},
 volume = {42},
 year = {2010}
}
,@article{15414,
 author = {Williams, M.C.},
 journal = {Metamorphosis},
 pages = {07--Mar},
 title = {Report on research findings concerning the life history and ecology of the Brenton Blue, <i>Orachrysops niobe</i> (Trimen) (Lepidoptera: Lycaenidae)},
 volume = {7},
 year = {1996}
}
,@phdthesis{15414,
 author = {Edge, D.A.},
 school = {0},
 title = {Ecological factors influencing the survival of the Brenton Blue butterfly <i>Orachrysops niobe</i> (Trimen) (Lepidoptera: Lycaenidae).},
 year = {2005}
}
,@article{15414,
 author = {Vlok  JHJ, Euston-Brown D.I.W. & Cowling R.M.},
 journal = {South African Journal of Botany},
 pages = {27–51},
 title = {Acock's Valley Bushveld 50 years on: new perspectives on the delimitation, characterisation and origin of subtropical thicket vegetation.},
 volume = {69},
 year = {2003}
}
,@article{15414,
 author = {Edge, D.A., Robertson, H.G. & van Hamburg, H.},
 journal = {African Entomology},
 pages = {253–262},
 title = {Ant associations at three potential breeding sites for the Brenton Blu butterfly, <i>Orachrysops niobe</i> (Trimen) (Lepidoptera: Lycaenidae).},
 volume = {16},
 year = {2008}
}
,@techreport{15414,
 author = {Edge, D.A.},
 institution = {0},
 title = {Brenton Blue Butterfly Special Nature Reserve: Environmental Management Plan Revision 2.},
 year = {2008}
}
,@article{15414,
 author = {Edge, D.A. & Pringle, E.L.},
 journal = {Metamorphosis},
 pages = {109–120},
 title = {Notes on the natural history of the Brenton Blue butterfly <i>Orachrysops niobe</i> (Trimen) (Lepidoptera: Lycaenidae).},
 volume = {7},
 year = {1996}
}
,]

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