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Western Monarch Populations Increase for the Second Year, but Our Work is Not Done

Jan 30, 2023


  • Population Trends

For over two and a half decades, the Xerces Society has led the Western Monarch Thanksgiving count, cataloging the rapid decline of the western monarch butterfly population. Last year, the monarch community was happily surprised by an increase of over 100-fold in western monarch populations compared to the 2021-2022 overwintering season. With today’s report of another population increase, the 2022-2023 overwintering season calls for similar cautious optimism. Over 250 volunteers surveyed 272 overwintering sites this winter, tallying a total of 335,479 monarch butterflies observed across the western overwintering sites, an increase of 88,242 monarchs!

The 2022-2023 overwintering total is exciting, but our work is not done. While there have been two years of population growth, the population is still well below historic numbers. As we have seen with the eastern and western monarch populations, monarchs are resilient, and population growth is possible if given the right conditions. With the severity and frequency of weather and climate conditions continuing to produce risky circumstances for monarchs, we must strive to support an even larger population to ensure this population size is at least maintained. To achieve this, we need to continue to increase our efforts to engage all hands on deck in restoring diverse habitat across the western landscape.

With monarchs' complex annual cycle, producing multiple generations and migrating across and occupying a large geographic area, many variables are worthy of further study. Researchers and community scientists across the West are contributing to answering several questions about the western monarch population.

  • To what extent is the timing and availability of early-season milkweed a primary limiting factor? The MJV provided funding for the 2022 and 2023 Western Monarch Mystery Challenge - check it out for an opportunity to contribute to our understanding of early-season monarch breeding activity.
  • How have winter breeding and the presence of non-native tropical milkweed affected migratory population dynamics? Professional research and community science efforts aim to understand better breeding population dynamics in the West, including resident populations. Easy, opportunistic sightings of monarchs and milkweeds are reported to the Western Monarch Milkweed Mapper. More volunteers are being trained and recruited for regular surveys of monarch breeding activity through the Monarch Larva Monitoring Project (MLMP). You can register for upcoming MLMP training here. The Integrated Monarch Monitoring Program also engages researchers in broader landscape-scale surveys on public and private lands.
  • To what extent is there an interchange between the eastern and western populations, and what are the origins of the overwintering monarchs? One program to help understand this question is the Southwest Monarch Study, which conducts ongoing research and engages volunteers who tag butterflies.
  • How is the use of pesticides impacting monarch production and survival? The Xerces Society recently released a publication discussing their worrisome findings in California’s Central Valley.

As we work together to collect data to understand western monarch population dynamics and threats, we must also scale up landscape conservation efforts. To help sustain and grow this population further, we must seek opportunities for producing more widespread and higher quality habitat across the western landscape. Here are a few ways to participate:
Thank you to our community of partners, other stakeholders, and the broader monarch conservation community, who work tirelessly to help monarchs, other pollinators, and the ecosystems they inhabit.
To read the Xerces Society’s western monarch population news release HERE and blog post HERE

  • Find more information on where to locate native milkweeds and other native wildflowers to support monarchs and other pollinators on our Milkweed Vendor Map.
  • Get involved in any of the community science programs mentioned above. Please note that to handle monarchs in California, you must have a scientific collection permit per the California Department of Fish and Wildlife.
  • Educate others about monarchs and pollinators and how they can be a part of the solution. A great way to become a monarch ambassador is by taking one of our upcoming Monarch Essentials courses.
  • Limit insecticide use that may cause unintended harm to monarchs and other beneficial insects.