The iconic black and orange monarch butterfly is known for its astonishing long-distance annual migration and reliance on milkweed as its obligate larval host plant. Though genetically similar, there are two subpopulations of monarchs in North America, with the eastern population overwintering in Mexico and breeding in the midwestern states, and the western population overwintering in coastal California and fanning out across the west from Arizona to Idaho to breed. Outside the U.S., there are at least 74 known populations of resident, non-migratory monarchs that have established around the world in the past 200 years, all with origins from the North American populations (Nial et al. 2019).
Both North American migratory populations have declined over the past twenty years due to a suite of interrelated factors including habitat loss in breeding and overwintering sites, habitat degradation, disease, pesticide exposure, and climate change. The western population has experienced dramatic swings, from a low of less than 2,000 in 2020-21 to over 200,000 in 2021-22 (Xerces Society Western Monarch Count). While it is unclear which of the many factors are driving these dynamics, insect population commonly fluctuate from year to year. The overall downward trend remains concerning, particularly if the threats are not ameliorated. Though more research is needed, a stable population for western monarchs is likely closer to the historic averages in the 1980's, which are estimated to have ranged between one to four million overwintering butterflies.
Conservation Status of Monarch Butterflies
In 2014, monarchs were petitioned to be listed under the federal Endangered Species Act. In December 2020, the U.S. Fish and Wildlife Service found that listing was warranted but precluded by other listing actions on its National Priority List. A revised decision is due in December 2024.
In California, monarchs are included on the California Department of Fish and Wildlife's (CDFW) Terrestrial and Vernal Pool Invertebrates of Conservation Priority list (PDF) and identified as a Species of Greatest Conservation Need in California's State Wildlife Action Plan. California law (Fish and Game Section 1002) prohibits the take or possession of wildlife for scientific research, education, or propagation purposes without a valid Scientific Collection Permit (SCP) issued by CDFW. This applies to handling monarchs, removing them from the wild, or otherwise taking them for scientific or propagation purposes, including captive rearing. To learn more about obtaining a Scientific Collecting Permit, see our SCP page.
CDFW's Monarch Conservation Work
CDFW is an active participant in the Western Association of Fish and Wildlife Agencies (WAFWA) effort to enhance western monarch conservation, along with the other member states Washington, Oregon, Idaho, Utah, Arizona, and Nevada. The 50-year Western Monarch Conservation Plan, adopted in 2019, establishes population size and habitat conservation goals and strategies. See WAFWA's Monarch and Native Insect Pollinator Working Group for more information on priority actions and focal regions.
CDFW also participates in the California Multi-agency Monarch and Pollinator Collaborative, a group of 13 state and federal agencies working to identify and enact shared priorities to catalyze monarch conservation in the state. Learn more about the group and access compiled resources at the Collaborative's website.
Monarch overwintering aggregations occur on five properties managed by CDFW and an additional two Department easements. In 2024 CDFW completed habitat assessments on four of the properties. We're currently planning management actions at those sites to reduce fire risk while enhancing resources that support monarchs. We are also working to protect and restore monarch breeding and migratory habitat on CDFW lands throughout the state.
Since 2021, CDFW has co-facilitated a plant materials working group with the Xerces Society focused on developing sources of early-season milkweed for restoration projects. The group currently has over 70 members from a variety of organizations. It is open to the public and you are welcome to join its quarterly meetings. To learn more, contact the CDFW Pollinator Coordinator at wildlifemgt@wildlife.ca.gov, and be sure to include 'plant materials working group' in the subject.
Frequently Asked Questions
The evolving monarch situation has raised many questions about monarch conservation, factors affecting the western population, and permitting requirements aimed at protecting the vulnerable migratory population. More detailed information on these topics is provided in our Frequently Asked Questions (FAQ) document (PDF).
Actions You Can Take to Support Monarchs
An effective response to monarch decline requires an 'all-hands-on-deck' approach, including participation from land managers and members of the public across the state. Actions we recommend include:
- Including native flowering plants in your home garden or restoration projects, focusing on early- and late-blooming species that support the early spring and fall migrations
- Planting native milkweed
- Ensuring plants you purchase from nurseries are pesticide-free
- Limiting pesticide use
- Becoming a community scientist by volunteering to collect data on monarchs and milkweed that help us make informed decisions: