Western Monarchs Experience Average Winter Declines at Overwintering Sites
By Isis Howard on 26 Mar, 2025
LINK: Western Monarch Count
LINK: (Read the full article–with photos–at Xerces.org)
LINK: Bounced back in 2021
LINK: Complete data is available
LINK: Native milkweed
LINK: Nectar plants
LINK: Habitat Kit program
LINK: Submit a public comment
LINK: Pesticides
LINK: Western Monarch Milkweed Mapper
LINK: Monarch Nectar Plant Database
LINK: Contact your elected officials
LINK: Monarch overwintering sites
Notice: Below is a list of 13 important links included on this page.
2. (Read the full article–with photos–at Xerces.org)
9. Pesticides
10. Western Monarch Milkweed Mapper
11. Monarch Nectar Plant Database
12. Contact your elected officials
13. Monarch overwintering sites
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Migratory western monarchs experienced a 41% seasonal decrease at California overwintering sites compared to peak November tally
This winter, community scientists and conservation professionals counted 5,407 monarch butterflies at 223 overwintering sites between December 28 and January 12, 2025. These latest findings from the Xerces Society’s Western Monarch Count indicate a 41% seasonal decrease between the sites monitored for both mid-season and late-season survey periods. (Read the full article–with photos–at Xerces.org).
Winter monarch declines are normal and have ranged between 28% to 58% in the past nine years. The average drop is 42%, which is very similar to this year’s decrease. It is likely that winter declines result from a combination of factors, including mortality from winter storms, predation, and butterflies leaving the overwintering sites.
As a whole, this overwintering season stood out as the second lowest on record, surpassed only by the 2020 count when fewer than 2,000 monarch butterflies were recorded during the mid-season and 1,069 during the late-season count. This year’s low numbers have rekindled concerns about the future of migratory western monarchs.
“It’s hard to know how many more record low years western monarchs can take,” says Isis Howard, a conservation biologist at the Xerces Society who coordinates the Western Monarch Count. “But if there’s one thing I want people to hold on to, it’s hope. Western monarchs bounced back in 2021, and I want to believe they can do so again.” With over 5,000 monarchs counted during the late-season period, there’s a chance monarchs can rebound over the spring and summer breeding seasons.
Central California hosts largest monarch populations
Similar to the mid-season trend, the majority of overwintering butterflies were observed in Santa Cruz County and Monterey County, California. Lighthouse Field State Beach remained the top site, with 1,500 monarchs reported during the late-season survey period. This number represents a slight increase from Lighthouse Field’s mid-season count, though the nearby site at Natural Bridges State Park dropped from 1,400 during the mid-season to zero monarchs during the late-season count. Complete data is available on the Western Monarch Count website.
California fires disrupt monarch surveys
Notably, fires throughout California overlapped with the late-season monitoring period, disrupting the last few days of surveys and prompting questions about fire and smoke impacts to monarchs. From December 2024 through January 2025, a series of destructive wildfires ripped through Los Angeles and San Diego Counties in California, getting very close to several known monarch overwintering sites, such as those adjacent to Malibu Creek. Also in January, a fire erupted at Vistra Energy’s Moss Landing Power Plant, a large battery storage facility in Monterey County, raising concerns about potential health and environmental impacts. Currently, there’s very limited research examining how increasing fires and smoke may affect migratory monarchs.
Time will tell what next year’s overwintering season has in store. In the meantime, it’s critical that we all play a role in bringing monarchs back.
Take Action Now to Help Recover Western Monarchs
Here are five ways you can support western monarch butterflies this spring:
Acknowledgements The Western Monarch Count is made possible by hundreds of dedicated volunteers and partners who collected data at overwintering sites, as well as funding from: California Association of Resource Conservation Districts, California Wildlife Conservation Board, Elizabeth Weber, The Maxwell/Hanrahan Foundation, Monarch Joint Venture, Nature’s Path Foods Inc., San Diego Zoo Wildlife Alliance, The Taggart Saxon Schubert Fund, U.S. Forest Service International Programs, and Xerces Society members.
- Plant native milkweed and nectar plants to restore breeding and migratory habitat. The Xerces Society’s Monarch and Pollinator Habitat Kit program is accepting applications through April 4, 2025–don’t miss out!
- Submit a public comment before May 19, 2025, in support of strong protections for monarch butterflies under the Endangered Species Act.
- Reduce your reliance on pesticides through eliminating their use, buying pollinator-safe nursery plants, supporting farms that use fewer pesticides, and advocating for changes in your community.
- Participate in community science efforts like the Western Monarch Milkweed Mapper project on iNaturalist and the Monarch Nectar Plant Database to answer key research questions.
- Contact your elected officials at the local, regional and state levels to ask that monarch overwintering sites in your area be protected.
Acknowledgements The Western Monarch Count is made possible by hundreds of dedicated volunteers and partners who collected data at overwintering sites, as well as funding from: California Association of Resource Conservation Districts, California Wildlife Conservation Board, Elizabeth Weber, The Maxwell/Hanrahan Foundation, Monarch Joint Venture, Nature’s Path Foods Inc., San Diego Zoo Wildlife Alliance, The Taggart Saxon Schubert Fund, U.S. Forest Service International Programs, and Xerces Society members.
