For over two and a half decades, the Xerces Society has led the Western Monarch Thanksgiving Count, cataloging the decline of the western monarch butterfly population. In 2021 and 2022, the monarch community was happily surprised by an increase in western monarch populations compared to the 2020 overwintering season, when only 1,914 were counted. However, the 2023-2024 western overwintering numbers demonstrated a decline. Over 400 volunteers surveyed 256 overwintering sites this winter, tallying a total of 233,394 monarch butterflies across the western overwintering sites.
The total count of 233,394 monarchs represents a 30.43% decrease compared to last year but is similar to the population in 2021. It is not uncommon for insect populations to observe year-to-year variations in their numbers, but longer term trends show a clear decline in the western monarch population. California overwintering groves were once covered in an estimated 4.5 million monarchs each winter. When the Western Monarch Thanksgiving Count began in 1997, over 1.2 million overwintering monarchs were observed at 101 sites.
Several factors, including temperature, rainfall, and the availability of milkweed and nectar resources across the western range influence the annual influx of butterflies to overwintering sites. 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, we must seek opportunities for producing more widespread and higher quality habitat across the western landscape.
Here are a few ways to support monarchs:
Plant native milkweeds- Find more information on where to locate native milkweeds and other native wildflowers to support monarchs and other pollinators on our Milkweed Vendor Map.
Participate in Community Science Programs- Learn more about community science programs in your area. 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 online courses.
Limit pesticide use that may cause unintended harm to monarchs and other beneficial insects. Learn more about pesticides and monarchs.
View the Western Monarch Call to Action to learn more about what you can do to support western monarchs.
The MJV would like to thank our network of partners, volunteers, and fellow pollinator conservation community who work tirelessly to help monarchs, other pollinators, and the ecosystems they inhabit. Together, we can sustain the monarch migration into perpetuity and serve as a flagship for the conservation of other plants and animals.
Xerces Society’s Press Release and Blog Announcement
Press release
English (also pasted below): https://xerces.org/press/western-monarch-count-tallies-233394-butterflies
Spanish: https://xerces.org/press/el-conteo-de-la-mariposa-monarca-occidenta-registro-233394-mariposas
Blog announcement
English: https://xerces.org/blog/western-monarch-count-tallies-233394-butterflies
Spanish: https://xerces.org/blog/el-conteo-de-la-mariposa-monarca-occidental-registro-233394-mariposas