The Western Monarch Thanksgiving Count (WMTC, www.westernmonarchcount.org) is a volunteer citizen scientist driven effort managed by the Xerces Society that has produced an annual estimate of the population of monarch butterflies that overwinter along the California coast since 1997. The data collected by WMTC participants has provided the most comprehensive estimate of the western monarch population’s annual size and trend over the past two decades. These data have been used in multiple studies resulting in peer reviewed publications, in the petition to list the monarch as an ESA threatened species, by the USFWS’s Species Status Assessment team, and in a recent population viability analysis by Dr. Cheryl Schultz.
While participation in the WMTC overall has expanded in recent years with the national increase in attention to monarch butterflies and their plight, coverage of many sites in southern California has declined. Sites that were historically monitored are no longer being visited. Many questions relevant to monarch conservation related to O.e. prevalence, movement, and phenology could be answered by increased citizen scientist participation from the San Diego area, where a year-round monarch breeding has been documented. To increase participation in this critical citizen science effort, the Xerces Society will host a training workshop in San Diego to teach about the WMTC and other monarch citizen science.