Western Monarch Numbers Remain at Historic Low

This is the third-lowest tally since the count began in 1997, following low numbers last winter and a weak summer breeding season. The three lowest counts in the program’s history have all occurred in recent years: 1,901 individual monarchs in 2020, 9,119 in 2024, and 12,260 in 2025. Western monarchs numbered in the low millions regularly in the 1980s. The increasing frequency of record-low years heightens ongoing concerns about the health and stability of the western monarch migration.

“Western monarchs are in serious trouble. The migration is collapsing,” said Emma Pelton, a senior conservation biologist with the Xerces Society. “We must move quickly to safeguard existing monarch habitat and restore and better manage the landscapes monarchs depend on, or else we risk losing one of North America’s most incredible natural phenomena. Our window for action is narrowing, and our conservation efforts must accelerate.”


Highest monarch count in Santa Cruz County

Despite low overall numbers, monarchs continued to roost in good numbers at sites in Santa Cruz. Natural Bridges State Beach recorded the highest count this season with 2,500 monarchs in early December. Xerces and partners deployed ultralight radio tags in Santa Cruz to better understand monarch movement during the overwintering period, information that could improve how overwintering habitat is managed.

Mid-season counts at other well-known sites include:

* Albany Hill, Alameda County: 221 butterflies
* Skywest Golf Course, Hayward, Alameda County: 510 butterflies across two sites
* Gill Tract Community Farm, Alameda County: 148 butterflies
* Pacific Grove Monarch Sanctuary, Monterey County: 188 butterflies
* Pismo State Beach Monarch Grove, San Luis Obispo County: 471 butterflies
* Ellwood Mesa, Santa Barbara County: 29 butterflies across nine sites
* Gaviota State Beach, Santa Barbara County: 425 butterflies across two sites
* Ocean Ave. Park, Ventura County: 178 butterflies


Development threatens remaining overwintering habitat

Experts say protecting and managing overwintering sites is vital to maintain the monarch migration. Loss of overwintering habitat on the California coast due to development remains a major threat to monarch survival.

“Since tracking began, over 60 monarch overwintering sites have been destroyed. In the last year alone, at least three active sites have been significantly damaged by extensive, inappropriate tree removal,” said Sarina Jepsen, director of the Xerces Society’s endangered species program. “Without adequate places for monarchs to overwinter, we will lose the migration.”

There are a number of active proposals to develop monarch groves. Local advocates in Hayward, CA are working to protect two overwintering groves in the Skywest Golf Course that are threatened by development plans for the Hayward Executive Airport. Overwintering habitat was also partially lost at a documented site in Vista Del Mar, Ventura, before constituents rallied to temporarily stop an order to remove additional eucalyptus trees to make way for a potential development.

In contrast, some communities have demonstrated that development can proceed while still protecting monarch overwintering habitat. At Gill Tract Community Farm in Albany, CA, collaboration among UC Berkeley, scientists, and community members protected and enhanced an overwintering site while allowing nearby student housing to move forward. Today, students and local partners steward the grove and support monarch monitoring with the Xerces Society.


Low numbers driven by long and short term stressors

While annual fluctuations in monarch numbers draw attention, scientists say the real concern is long-term decline of monarchs and other butterflies driven by habitat loss, pesticides, and climate change. Research led by Drs. Cheryl Schultz and Elizabeth Crone showed that western monarchs have declined by approximately 10% per year since the 1980s, suggesting this year’s low numbers reflect an ongoing trend rather than a sudden crash.

“When populations get this small, they become far more vulnerable to both short-term stress and long-term pressures,” said Isis Howard, a conservation biologist with the Xerces Society who coordinates the Western Monarch Count. “With low overwintering numbers becoming more common, monarchs have fewer chances to rebound from extreme weather or pesticide exposure.”


A call to action to save the monarchs

“While another year of low numbers is bad news for western monarchs, the good news is that everyone can play a role in bringing them back from the brink,” said Pelton. “If we all do what we can, we can make a real and lasting difference.”

The Xerces Society is inviting all Californians to make a tangible difference this year through the Western Monarch Call to Action. Priority actions to recover the population include:

* Avoid using pesticides, especially insecticides, which threaten monarchs and other pollinators.
* Create and maintain monarch habitat year-round by planting regionally appropriate native flowers and native milkweeds. Qualifying individuals can apply for a free habitat kit.
* Advocate for protection of overwintering sites.
* Participate in community science.


Top photo: A monarch in Santa Cruz rests after being affixed with an ultralight radio tag. The Xerces Society and partners and studying monarch movement during the overwintering period to improve how habitat is managed. Image credit: Ashley Fisher, Xerces Society


Acknowledgments

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: The California Wildlife Conservation Board, California Association of Resource Conservation Districts, Cinco Hermanos Fund, Elizabeth Weber, Maxwell/Hanrahan Foundation, Monarch Joint Venture, Nature's Path Foods Inc., San Diego Zoo Wildlife Alliance, U.S. Forest Service International Programs, and Xerces Society members.

https://www.xerces.org/press/western-monarch-numbers-remain-at-historic-low