The Xerces Society for Invertebrate Conservation, Groundswell Coastal Ecology, California Department of Parks and Recreation, and the U.S. Fish and Wildlife Service have developed a western monarch butterfly overwintering site management plan that also serves as a template for land managers at other overwintering sites.
The plan also outlines suggested public outreach and engagement activities, monarch mortality monitoring, and data collection that can be used to inform other research about western monarch migration and overwintering habits.
Monarch butterflies in western North America typically arrive at overwintering sites along the California coast in September or October, and remain through early spring. These overwintering sites offer the microclimatic conditions monarch butterflies need to survive winter in western North America.
Overwintering sites along the western U.S. coast are found from Mendocino County, California to Baja California, Mexico. In recent years, many sites have become unsuitable due to multiple factors including, habitat degradation, development, and aging trees. As a result overwintering population numbers have declined by more than 95 percent in the last 30 years.
Funding for the research, development and implementation of the Monarch Butterfly Overwintering Site Management Plan for Lighthouse Field State Beach comes from the U.S. Fish and Wildlife Service Coastal Program, the National Fish and Wildlife Foundation and grants secured by Groundswell Coastal Ecology.