Pale yellow dune moth (Copablepharon grandis) COSEWIC assessment and status report: chapter 8
Limiting Factors and Threats
The limiting factors and threats to C. grandis in Canada are the following:
Habitat Loss: Decline of semi-open dune habitat (Hugenholtz and Wolfe 2005, Wolfe and Thorpe 2005), although it may be proceeding somewhat more slowly than decline of active dunes, is likely to reduce habitat further over the next few decades.
Cattle Grazing: Grazing is considered a possible threat to C. grandis. It may maintain sparsely vegetated sandy habitats (Figures 6 and 8). However, grazing may result in soil compaction and browsing of vegetation that is used for larval feeding, and may also crush eggs, larvae, or pupae.
Figure 8. Example of the effects of cattle grazing on sand dune habitat. The portion of the dune on the right side of the fence is affected by cattle use and shows trail formation, reduced vegetation cover, and substantially greater open sand. The habitat on the left side of the fence is more stable with higher vegetation cover. Photo from the Straw Roadarea of the Great Sand Hills, SK. Photo by N. A. Page (2005).
Population Isolation and Demographic Collapse: Populations of C. grandis in Canada may be at risk from demographic collapse because of their isolation. Ecological theory predicts that the risk of a subpopulation going extinct in a single patch is reduced with increasing numbers of surrounding subpopulations (Hanski, 1982). This risk reduction is caused by the “rescue effect” that allows immigration between patches to prevent the complete collapse of a group of subpopulations. Development of the land between suitable habitats may increase the risk of extirpation. The lack of information on the population structure of C. grandis makes it difficult to assess the risk of demographic collapse; it is considered a possible threat.
Land and Infrastructure Development: Activities such as road building, petroleum infrastructure construction, and excavation of water holes for cattle that result in direct loss or disturbance to dry grasslands, sandy habitats, and badlands are considered a possible threat to C. grandis. Copablepharon grandis may benefit from some forms of human disturbance.
Recreation: Recreational activities, including horse riding, ATV riding, off-road vehicle use, walking and hiking, may be intensive in some C. grandis habitats and result in vegetation loss and soil disturbance. Recreation may affect the population in the Spirit Dunes, Spruce Woods Provincial Park. Recreation is considered a possible threat to C. grandis in Canada
Collecting specimens for research purposes is considered to have an insignificant effect on C. grandis.
Conservation concerns in similar species
All known Canadian Copablepharon species are associated with dune habitats, which are rare in Canada. Copablepharon viridisparsa shares similar habitats in the Canadian prairies with C. grandis and is being assessed by COSEWIC (COSEWIC, 2007a). It is noteworthy that one Copablepharon taxon, Copablepharon viridisparsa ssp. hopfingeri Franclemont is the only moth taxon known to have been extirpated from western Canada (Lafontaine and Troubridge, 1998). Historically, it occurred in a small site with sandy soils near Castlegar, BC. Copablepharon fuscum (Sand-verbena Moth) is the only Copablepharon species west of the Cascade Mountains. It is very rare in southwestern BC (three to five populations) and was designated as Endangered by COSEWIC in 2004. It may be more sensitive to change than C. grandis because it relies on a single host plant.