Xerces society monarch butterfly

The Western Monarch Count is a product of annual monitoring efforts at monarch overwintering sites.

Each year between October and March, community scientists and conservation professionals collect data at monarch overwintering sites located along the California coast, Northern Baja California and a few inland sites in California and Arizona.

Decades of data from this community-powered initiative highlight the steep decline of migratory western monarchs.

Xerces society monarch butterfly

These data are compiled and entered into the Xerces Society’s Western Monarch Overwintering Sites (WMOS) database which also includes historic observations prior to 1997 when the WMC began. A public summary of WMC data is available below; this data summary is updated each season once survey data are vetted.

Download data for all years (1997-2024)

*NOTE: Data were last updated on March 19, 2024.