Monarch Butterfly

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. 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 in North America (Nial et al. 2019(opens in new tab)).

The North American migratory populations, however, have experienced dramatic declines 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 most recent population census(opens in new tab) of the western population, conducted annually by The Xerces Society for Invertebrate Conservation, revealed that fewer than 2,000 individual butterflies currently seek shelter in California's coastal groves. Western monarch numbers have dropped by 99% from an estimated 4 million butterflies just twenty years ago.

Conservation Status of Monarch Butterflies

In 2013, 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(opens in new tab) by other listing actions on its National Priority List. The monarch is currently slated to be listed in 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)(opens in new tab) and identified as a Species of Greatest Conservation Need in California's State Wildlife Action Plan. California law prohibits handling monarchs, removing them from the wild, or otherwise taking them for scientific research or propagation purposes without a valid Scientific Collection Permit (SCP). To learn more about obtaining a collection permit, see our SCP page.

Actions to Support Monarchs

CDFW is an active participant in the Western Association of Fish and Wildlife Agencies (WAFWA) effort to enhance western monarch conservation with the other member states of Washington, Oregon, Idaho, Utah, Arizona, and Nevada. The 50-year Western Monarch Conservation Plan (PDF)(opens in new tab), adopted in 2019, establishes population size and habitat conservation goals, strategies. See WAFWA's Monarch Working Group(opens in new tab) for more information on priority actions and focal regions.

The collapse of the migratory monarch population has been steep and rapid. An effective response requires participation from the public and land managers across the state to help kick-start recovery efforts. CDFW has partnered with the U.S. Fish and Wildlife Service, The Xerces Society for Invertebrate Conservation, and California Department of Parks and Recreation to develop priority regions and actions to support monarchs throughout the State. Depending on where you live, these actions 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. We especially need information for the period February through April.