Western chorus frog: supplemental information on boundary lines and designatable units

The purpose of this supplemental information is two-fold. The first objective is to clarify the location of the boundary that separates the two Designatable Units (DUs) of Western Chorus Frog that were assessed by COSEWIC in 2008. The DU boundary for Western Chorus Frog is defined explicitly by the line demarcating the Great Lakes/St. Lawrence-Canadian Shield and Carolinian faunal provinces. This line is indicated in Figure 4 of the status report; it is the northern edge of the red-shaded Carolinian DU.

The second objective of the supplemental information is to report the findings of a re-analysis of the Marsh Monitoring Programme (MMP) data from 1995 through 2006. COSEWIC’s assessments of the DUs were based, in part, on these data. The re-analysis indicated that the Great Lakes/St. Lawrence-Canadian Shield DU declined 42.6% between 1995/96 and 2005/06. This decline is greater than the 30% reported in the status report (Figure 6), thus supporting COSEWIC’s status assessment of Threatened for this DU. The MMP data did not reveal a statistically significant unidirectional trend in abundance in the Carolinian DU. COSEWIC assessed the Carolinian DU as Not at Risk.

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