Island Tiger Moth,Grammia Complicata
Total Page:16
File Type:pdf, Size:1020Kb
COSEWIC Assessment and Status Report on the Island Tiger Moth Grammia complicata in Canada THREATENED 2013 COSEWIC status reports are working documents used in assigning the status of wildlife species suspected of being at risk. This report may be cited as follows: COSEWIC. 2013. COSEWIC assessment and status report on the Island Tiger Moth Grammia complicata in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. ix + 58 pp. (www.registrelep-sararegistry.gc.ca/default_e.cfm). Production note: COSEWIC would like to acknowledge Jennifer Heron for writing the status report on Island Tiger Moth, Grammia complicata, in Canada, prepared under contract with Environment Canada. This report was overseen and edited by Dr. Laurence Packer, Co-chair of the Arthropods Specialist Subcommittee and Donna Hurlburt, Co-chair of the Aboriginal Traditional Knowledge 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 E-mail: COSEWIC/[email protected] http://www.cosewic.gc.ca Également disponible en français sous le titre Ếvaluation et Rapport de situation du COSEPAC sur L’apantèse compliquée (Grammia complicata) au Canada. Cover illustration/photo: Island Tiger Moth — Cover photograph by Jennifer Heron. Her Majesty the Queen in Right of Canada, 2013. Catalogue No. CW69-14/668-2013E-PDF ISBN 978-1-100-22395-7 Recycled paper COSEWIC Assessment Summary Assessment Summary – May 2013 Common name Island Tiger Moth Scientific name Grammia complicata Status Threatened Reason for designation This near endemic moth has a small distribution and is restricted to only 5 locations in the Georgia Basin in British Columbia. Much of its habitat has been destroyed and the quality of what remains is declining due to ongoing residential and commercial development, recreational activities, invasive or non-native species, and vegetation succession that has changed due to disruption of former fire regimes. Occurrence British Columbia Status history Designated Threatened in May 2013. iii COSEWIC Executive Summary Island Tiger Moth Grammia complicata Wildlife Species Description and Significance Island Tiger Moth (Grammia complicata Walker) is a medium sized moth (wingspan 32 mm to 40 mm) in the family Erebidae, subfamily Arctiinae. The upper wing surfaces vary from dark brown-black interlaced with whitish to pale orange patterns along the wing veins; to the converse, with an orange-peach background with dark brown-black vein-like patterns. The hind wings are typically lighter than the forewings, pale orange, with brown dots towards the outer wing margins which are also brown. The head, thorax and abdomen are dark brown-black with peach-orange markings. In general,Tiger moth (Grammia spp.) larvae are up to 6 cm long, have black - orange lateral stripes and are densely covered in dark hairs. This species was recently (2009) separated from the Ornate Tiger Moth based on morphological and genetic evidence. Distribution Island Tiger Moth is endemic to the Georgia Basin. With the exception of one record from Orcas Island, Washington State, the moth is a Canadian endemic. On Vancouver Island, Island Tiger Moth ranges from the Greater Victoria area north to Comox and there are records from Thetis, Sandy and Savary Islands. Based on historical and current records, the species’ Canadian range is 3600 km2. Island Tiger Moth is considered extant at five sites in B.C.: Goose Spit, Sandy Island, Nanoose Hill, Savary Island and Thetis Island. The habitat at some sites span multiple landowners. The record on Thetis Island is considered old (1975) although there is much potential habitat on the island and the moth may be present. Based on the threat of land development (due to land ownership), there are 5 – 8 locations. iv Habitat Island Tiger Moth has been recorded from a variety of habitat types including open and grassy Garry Oak forest; open moist to dry meadows; grassy shoreline sandy areas and in more stabilized, sparsely vegetated areas in sand dunes. The Moths of the genus Grammia typically do not inhabit closed forest habitats. The larval host plants for Island Tiger Moth are unknown, although tiger moths are known to be generalist herbivores. There is an early record of larvae being collected on introduced English Plantain. Biology According to museum and collection records Island Tiger Moth adults are active from May through late July. Larvae have been collected in both early March and late July. Females have heavy bodies and comparatively small wings: they are incapable of more than short distance dispersal. Population Sizes and Trends Information on Island Tiger Moth population sizes and trends in B.C. is minimal. Most records are historical or a single individual at one site on one date. Threats and Limiting Factors Threats to Island Tiger Moth and its associated habitat include residential and commercial development, recreational activities, and vegetative succession from both invasive and native species. Protection, Status, and Ranks Island Tiger Moth is not protected by any existing legislation. Within provincial parks parks and protected areas, lands managers are aware of the moth’s records within parks, although detailed provisions in park management planning have yet to be addressed. The B.C. Conservation Data Centre has not assigned the moth a conservation status rank, although preliminary status ranking places the moth at S1 Red-listed (Critically Imperilled). The global status rank is G1G2 (critically imperiled). The Canadian and B.C .general status rank is “May Be At Risk”. v TECHNICAL SUMMARY Grammia complicata Island Tiger Moth Apantèse compliquée Range of occurrence in Canada: British Columbia Demographic Information Generation time 1 yr Is there an [observed, inferred, or projected] continuing decline in Inferred decline due to habitat number of mature individuals? loss Estimated percent of continuing decline in total number of Unknown mature individuals within [5 years or 2 generations] [Observed, estimated, inferred, or suspected] percent [reduction Unknown or increase] in total number of mature individuals over the last [10 years, or 3 generations]. [Projected or suspected] percent [reduction or increase] in total Unknown number of mature individuals over the next [10 years, or 3 generations]. [Observed, estimated, inferred, or suspected] percent [reduction Unknown or increase] in total number of mature individuals over any [10 years, or 3 generations] period, over a time period including both the past and the future. Are the causes of the decline clearly reversible and understood Not reversible; somewhat and ceased? understood; not ceased Are there extreme fluctuations in number of mature individuals? Unknown; not likely. Extent and Occupancy Information Estimated extent of occurrence 1881 km² 1881 km² based on recent sites (since 1975) 3600 km² based on historical and recent sites; Index of area of occupancy (IAO) 20 km² 76 km² based on historical and recent sites; 20 km² based on five recent sites (Figure 3) Is the total population severely fragmented? Likely, recent sites are >7 km from the next closest site and are separated by ocean. Loss of any one site would have a large impact on the total Canadian population and result in a large range gap Number of locations 5 - 8 based on the potential of development, based on land ownership (see Figure 2 and Table 2) Is there an [observed, inferred, or projected] continuing decline in Yes, inferred, based on habitat extent of occurrence? loss and fragmentation of habitats See Definitions and Abbreviations on COSEWIC website and IUCN 2010 for more information on this term. vi Is there an [observed, inferred, or projected] continuing decline in Yes, inferred, based on habitat index of area of occupancy? loss and fragmentation of habitats Is there an [observed, inferred, or projected] continuing decline in A reduction can be projected number of populations? based on habitat loss and fragmentation of habitats. Is there an [observed, inferred, or projected] continuing decline in Yes, inferred, based on habitat number of locations*? loss and fragmentation of habitats Is there an [observed, inferred, or projected] continuing decline in Yes, inferred, based on habitat [area, extent and/or quality] of habitat? loss and fragmentation of habitats Are there extreme fluctuations in number of populations? Unlikely Are there extreme fluctuations in number of locations? Unlikely Are there extreme fluctuations in extent of occurrence? No Are there extreme fluctuations in index of area of occupancy? Unlikely Number of Mature Individuals (in each population) Population N Mature Individuals Unknown Total Unknown Quantitative Analysis Probability of extinction in the wild is at least [20% within 20 years or 5 Not Applicable generations, or 10% within 100 years]. Threats (actual or imminent, to populations or habitats) Development (urban, recreational, infrastructural), succession, invasive species, demographic collapse, BtK spraying, climate change-related impacts Rescue Effect (immigration from outside Canada) Status of outside population(s)? Known from only 1 population in Washington state, most likely at greater conservation risk there Is immigration known or possible? Highly improbable given limited vagility of females Would immigrants be adapted to survive in Canada? Probably Is there sufficient habitat for immigrants in Canada? Perhaps Is rescue from outside populations likely?