Skip to Content

Record Low Number of Overwintering Monarch Butterflies in California - They Need Your Help!

Jan 17, 2019


  • Population Trends

Article based on an original press release and blog by the Xerces Society.

PORTLAND, Ore.; Thursday, 1/17/19

The population of monarch butterflies overwintering in California has fallen to the lowest level ever recorded.

Surveys done by volunteers with the Western Monarch Thanksgiving Count found only 28,429 butterflies, an 85.2% fall from the previous year—and a 99.4% decline from the number of monarchs in the state in the 1980s. The results of the count were released Thursday by the Xerces Society for Invertebrate Conservation, along with a Western Monarch Call to Action.

[Graph depicting the results of the Western Monarch Thanksgiving Count]

For every 160 monarchs there were in the 1980s, there is now only one.

Faced with these alarming numbers, The Xerces Society has worked with monarch scientists at institutions across the West to develop the Western Monarch Call to Action, a five-point rapid-response action plan to rescue the western population of the monarch butterfly.

“It’s easy to give up when faced with news like this,” said Emma Pelton Endangered Species Conservation Biologist with the Xerces Society. “But doing nothing is not an option.”

The call to action is a set of rapid-response conservation actions that, if applied immediately, can help the western monarch population bounce back from its extremely low 2018–19 overwintering size.

“We recognize and support longer-term recovery efforts in place for western monarchs such as the WAFWA plan and MJV implementation plan. This call to action, however, identifies steps that can be done in the short-term (the next few weeks or months up to one year), to avoid a total collapse of the western monarch migration and to set the stage for longer-term efforts to have time to start making a difference,” stated the Xerces Society blog post.

The Top 5 Immediate Actions to Save Western Monarchs

The most immediate priority in the coming weeks is to restore breeding and migratory habitat in California. It is vital to ensure monarchs have nectar to fuel their flight and milkweeds on which they can lay their eggs when they leave the overwintering sites. This is something that everyone in California can help with right now: plant early blooming native flowers and milkweed to restore breeding and migratory habitat. Monarchs will use plants growing in gardens, parks, along railroads, on farms and anywhere else they can find them.

If you are elsewhere in the west, your help is also needed to identify and enhance habitat across the western states where monarchs fly to breed during the summer.

Protecting the monarch overwintering sites is of equal importance to ensuring monarchs have flowers and milkweed. Each year, the groves monarchs shelter in are destroyed or damaged by development or inappropriate tree trimming. This needs to be halted and the groves given adequate protection and management, so that monarchs have a place to return to next fall.

There are important questions that remain unanswered about monarchs, such as a detailed understanding of where they go right after they leave the overwintering sites. People can look for monarchs and report what they see to the online Western Monarch Milkweed Mapper project to help inform conservation strategies.

 Another important action is reducing pesticide use, so monarch have clean places to feed and breed.

Join the Call to Action

Many state and federal agencies, farmers, nonprofits and individuals are increasing their conservation efforts, but more work needs to be done.

“There are things that can be done by anyone in any place. We urge you to join us and our colleagues in the western monarch science and conservation community in taking meaningful, swift action to help save western monarchs”, said Sarina Jepsen, director of the Xerces Society’s endangered species program.

It is urgent that we undertake immediate conservation actions across California and the west if we hope to save the western monarch migratory phenomenon.

“Can we promise that monarchs will recover and fill California’s skies again?” said Xerces Society Executive Director Scott Hoffman Black. “Sadly, no. But we are not going to be the generation that witnessed this loss and stood by and did nothing.”

The monarch population in eastern United States, which migrates to Mexico, has declined by more than 80% in the last 20 years. However, it appears to have not suffered the same alarming fall in numbers this year. The official eastern monarch population estimate for 2018 has not yet been released at the time of this article.

To read the Western Monarch Call to Action and download a copy, visit


The Monarch Joint Venture is a national partnership of federal and state agencies, non-governmental organizations, businesses and academic programs working together to conserve the monarch butterfly migration. The content in this article does not necessarily reflect the positions of all Monarch Joint Venture partners. Header photo by The Xerces Society/Candace Fallon.