Western Monarch Count Tallies 233,394 Butterflies

“Last year’s winter storms meant we entered the spring breeding season with fewer butterflies and saw lower numbers this summer, so it is not surprising that the overwintering population is down,” said Emma Pelton, a monarch conservation biologist with the Xerces Society. “It’s difficult to predict how conditions during any single year will influence the population, but we do know that western monarch numbers need to be much higher before we consider this a recovery.”

The western monarch population is geographically distinct from eastern monarchs that migrate from eastern Canada and the United States to central Mexico each year, and instead tracks butterflies migrating from the western U.S. and Canada to coastal California and northern Baja, Mexico, as well as small interior sites in California’s Saline Valley and the Phoenix area. Like their eastern counterparts, the migration takes place over multiple generations of butterflies, with the final generation overwintering in large clusters sheltered in groves of trees.

Central Coast hosts the largest overwintering sites

The largest count at a single location was 33,080 monarchs at an overwintering site in Santa Barbara County owned by The Nature Conservancy. The site hosted the largest number of butterflies in 2022 as well, and is not open to the public. The second largest count was 16,038 monarchs at the Pismo State Beach Monarch Butterfly Grove, followed by 10,029 at the Morro Bay Golf Course in San Luis Obispo County.

High counts for other popular sites included (listed from north to south):

* 305 butterflies at Albany Hill in Alameda County
* 1,093 at the Monarch Bay Golf Course in San Leandro County
* 10,000 at Lighthouse Field State Beach in Santa Cruz County
* 6,500 at Natural Bridges State Beach in Santa Cruz County
* 6,547 at the Pacific Grove Monarch Sanctuary in Monterey County
* 15,206 across the Ellwood Mesa complex (multiple sites) in Santa Barbara County
* 319 at Camino Real Park in Ventura County

Additionally, participants identified four newly-recognized monarch overwintering sites, plus a handful of potential sites which will be surveyed again next season.

More than 400 volunteers joined this year’s monarch count

Coordinated by the Xerces Society and partners across the western U.S., more than 400 volunteers joined the effort this year, rising early to count clustered butterflies for the Thanksgiving period that ran November 11 through December 3, when overwintering numbers are typically at their peak.

"Volunteers and partners are the heartbeat of the Western Monarch Count community science effort,” says Isis Howard, who coordinates the count for the Xerces Society. “They embody a collective commitment to the conservation of western monarch butterflies."

Notably, a visitor to the Pacific Grove Monarch Sanctuary in Monterey County, California, spotted a butterfly that had been tagged by the Southwest Monarch Study in northern Utah, meaning it had traveled over 700 miles.

Western monarchs remain imperiled

Despite ongoing efforts to preserve their migration, western monarchs face significant challenges, including habitat destruction, pesticide exposure, and extreme weather exacerbated by climate change. Some population fluctuation is normal, but the overall trend continues to be below historic norms. When invertebrate populations are in decline, it’s common to witness populations fluctuate year to year.

“There is still very little meaningful protection for migratory monarch butterflies and their overwintering habitat,” said Pelton. “Hopefully, the U.S. Fish and Wildlife Service’s upcoming listing decision under the federal Endangered Species Act will provide protection to the important places that monarchs rely on each winter.”

When populations are low, small changes in factors like temperature, rainfall, predation and availability of milkweed and nectar resources can strongly influence each generation’s survival rates. The newly formed Western Monarch Overwintering Science Initiative (M.O.S.I) will be looking deeper at these factors, including tracking the butterflies and studying conditions at overwintering sites.

Everyone can take action to protect western monarchs and other wildlife. To get started:

* View the Western Monarch Call to Action to learn more about priority zones and actions.
* Plant native milkweed and nectar plants in your garden and community spaces. (Milkweed should not be planted in overwintering zones.)
* Reduce or avoid herbicide and insecticide use, especially systemic insecticides.
* Share your knowledge and passion for monarch conservation with friends and family.
* Volunteer for a community science effort or local conservation cause.
* Take the Pollinator Protection Pledge to commit to working every day to protect pollinators and their habitats.


Photo: Monarchs clustering on a Monterey cypress after a light rain at Lighthouse Field State Beach in Santa Cruz County, November 2023. Image credit: Isis Howard, Xerces Society


About the Western Monarch Count

The Western Monarch Count (WMC) is a community science effort to collect data on western monarchs and their habitat during the overwintering season, which occurs from approximately October to March. The Thanksgiving count is the first of two official survey periods during the season, and it usually captures the height of clustering monarchs. The WMC is managed by the Xerces Society and count co-founder, Mia Monroe. Participants follow a standard protocol to survey overwintering habitat and estimate the number of butterflies in coastal California as well as northern Baja, Mexico and the greater Phoenix, AZ area. Data from the WMC are used to improve our understanding of the western monarch population status and their conservation needs.

Acknowledgements

A huge thank you to the hundreds of dedicated volunteers who collected data at overwintering sites. And, thank you to our western monarch conservation funders, who make this work possible: California Department of Fish and Wildlife, California State Parks Foundation, California Wildlife Conservation Board, Google.org, U.S. Forest Service International Programs, The Marion R. Weber Family Fund, Monarch Joint Venture, National Fish and Wildlife Foundation, San Diego Zoo Wildlife Alliance, The Taggart Saxon Schubert Fund, USDA Natural Resources Conservation Service, USDOI Bureau of Land Management, US Fish and Wildlife Service, and Xerces Society members.


https://www.xerces.org/press/western-monarch-count-tallies-233394-butterflies