Pale yellow dune moth (Copablepharon grandis) COSEWIC assessment and status report: chapter 7

Population Sizes and Trends

Search effort

Multiple light-traps (bucket traps with 12 V UV lights) were set in ten sites in sparsely vegetated sandy habitats in southern Saskatchewan and Alberta between July 31–August 6, 2004 and July 23–27, 2005. A total of 28 traps were installed in potential C. grandis habitat.

Copablepharon grandis was captured in six traps from four sites: Dundurn DND Base south of Saskatoon, SK; Sounding Lake area, SK; CFB Wainwright, AB; and Suffern Lake Regional Park, SK. Three of these localities are new records for C. grandis, and the record from Dundurn confirms the moth’s continuing presence near Saskatoon that was originally described in 1939. Additional sampling was undertaken by G.G. Anweiler and B.C. Schmidt and a new locality was found near Chauvin, SK. A summary of the 2004–2005 trapping results and site information is presented in Appendix 2. Figure 3 shows the location of known populations and unsuccessful trap sites.

Sampling in 2004 and 2005 provided new information on population distribution, and, more importantly, it increased our understanding of habitat requirements. Trapping was generally undertaken with multiple traps which allowed sampling over a range of habitat conditions (e.g., active and semi-stable dunes).

The species has not been seen in the Calgary area or to the south in Alberta since at least 1913 despite more active moth trapping in recent decades. 

Abundance

A total of 18 C. grandis specimens were captured in 2004–2005 ranging from 1 per trap to 12 per trap (mean of three per trap). Schmidt (pers. comm., 2005) captured 15 C. grandis in five ultraviolet light-traps while sampling for Schinia species in a sandy grassland near Chauvin, SK. These captures represent less than 1% of the total number of moths captured in these sites, an indication of the low local abundance of the species. A summary of the 2004–2005 trapping results in presented in Appendix 2.

Because of the low number of C. grandis captured and the inherent uncertainties in measuring capture success, available habitat, and other factors, a population estimate cannot be calculated for the species. Light-trap captures provide a biased estimate of population size and should be used cautiously for characterizing population density.

Fluctuations and trends

There is no quantitative information on population fluctuations and trends for C. grandis. The inherent difficulty in assessing population sizes, variability, and trends in rare, nocturnal insects has greatly reduced the potential for detailed population information.

Rescue effect

The population at Turtle Mountain, North Dakota, USA is approximately 250 km south of the closest Canadian locality at Spruce Woods Provincial Park in Manitoba. Recolonization over this distance is unlikely.

Page details

Date modified: