Newly published papers shed light on western monarch conservation needs.

Western monarch researchers and community scientists have been busy, contributing information vital to understanding the situation facing this imperiled population of America’s most well-known butterfly.

Four new studies on western monarchs were recently published as part of the special issue of Frontiers in Ecology and Evolution titled North American Monarch Butterfly Ecology and Conservation (the online issue has been gradually published since May 2019, and these papers are each available for free). A fifth study on western monarchs is also about to be published—more details below. All of these studies draw, at least in part, on the findings of community science projects like the Western Monarch Milkweed Mapper—which has collected 53,097 records of monarchs and milkweeds in total, including nearly 500 sightings in 2019 alone.

Together, these studies contribute to our understanding of the western monarch population, including where monarchs and milkweeds occur, the habitats they rely on, and what actions are most likely to help the population recover. These papers also underscore the importance of community science efforts, which have provided key information. At the end of this blog post, we provide a list of ways in which community members can contribute to monarch research efforts—in the western United States and beyond.

Summaries of New Western Monarch Studies

• Western monarch population plummets: status, probable causes, and recommended conservation actions by Pelton et al. The paper puts the all-time low, 2018-2019 overwintering population in context, highlights the window during the annual life cycle when the population most likely declined, reviews probable causes of the population’s long-term decline, and recommends steps that the public, policy makers, and land managers can take to recover western monarchs. This paper builds off Xerces’ Western Monarch Call to Action and draws from the Western Monarch Thanksgiving and New Year’s Count, the Xerces Society’s community science project at western monarch overwintering sites, as well as ongoing field research by Xerces’ staff in partnership with Washington State University and Tufts University on Department of Defense Air Force bases across the western U.S.
• Host plants and climate structure habitat associations of the western monarch butterfly by Dilts et al. This study consists of habitat suitability models for breeding and migratory habitat for the western monarch butterfly and western milkweed species, showing which geographic areas are most suitable for the species. This research comes out of a multi-year partnership between the University of Nevada-Reno, US Fish and Wildlife Service-Pacific Region, and the Xerces Society. The models were developed based on field surveys and data from the Western Monarch Milkweed Mapper, a database and community science project which Xerces developed with the Idaho Department of Fish and Game, Washington Department of Fish and Wildlife, and the U.S. Fish and Wildlife Service. Check out how the models are already being used for conservation, planning, and research here. Contact [email protected] if you are interested in obtaining copies of the models.
• Monarch butterfly distribution and breeding ecology in Idaho and Washington by Waterbury et al. This paper offers a detailed picture of the distribution and breeding patterns of monarchs in these states, based on extensive statewide surveys by the Idaho Department of Fish and Game and the Washington Department of Fish and Wildlife for milkweeds and monarchs. All records have also been added to the Western Monarch Milkweed Mapper.
• Modeling current and future potential distributions of milkweeds and the monarch butterfly in Idaho by Svancara et al. This study uses the same modeling approach as Dilts et al. 2019, but applies a finer scale look at distribution in Idaho as well as forecasting distribution under climate change. It uses data from both the Waterbury et al. 2019 study, the Western Monarch Milkweed Mapper, and other sources.

Additional Studies of Note

• Coming soon, in the journal Ecological Applications: Why are monarch butterflies declining in the west? Understanding the importance of multiple correlated drivers by Crone et al. This study examines how the size of the western monarch’s overwintering population may be affected by different land use (e.g., coastal development, pesticide use) and climate stressors. The authors conclude that we need to simultaneously work now on protecting and restoring monarch breeding and overwintering habitat and also call for more studies to untangle which stressors are the most responsible for the population’s current status.
• Finally, while not focused on western monarchs specifically, a noteworthy new study discusses monarch rearing. Contemporary loss of migration in monarch butterflies by Tenger-Trolander et al. in Proceedings of the National Academy of Sciences suggests that rearing and releasing monarchs obtained from commercial breeders—as well as rearing wild-collected monarchs in a controlled indoor environment—may have negative impacts on monarch migration and genetics. (Note: The full text can only be viewed with purchase; the summary, abstract, and footnotes can be viewed for free at the link above.) While more research is needed, this study provides support for recommendation by Xerces and many monarch researchers that rearing monarchs is not an appropriate conservation strategy for the species and carries risks. See Keep Monarchs Wild: Why Captive Rearing Isn’t the Way to Help Monarchs to learn more.

The Value of Community Science

The research papers above all relied on data collected by people like you, as part of community science projects. Community science is invaluable to contributing to our understanding of the western monarch and helps the conservation community to focus on the most important ways to conserve this beloved butterfly.

You can participate in community science projects which are vital to monarch research by joining people all over Canada, the U.S., and Mexico in collecting data on monarchs and milkweeds as part of the 2019 International Monarch Monitoring Blitz, from July 27 to August 4. If you live in the U.S. and are west of the Rocky Mountains, contribute your observations to the Western Monarch Milkweed Mapper; if you live east of the Rocky Mountains, contribute to Monarch Joint Venture’s Monarch Larva Monitoring Project; in Canada, check out Mission Monarch; if you’re in Mexico, we encourage you to contribute to Naturalista. We also recommend reporting first sightings of monarchs throughout these three countries to Journey North.

Already a user of iNaturalist? Check out the new Western Monarch Milkweed Mapper project to make contributing western records even easier on this popular platform.

Looking for More Ways to Help?

Check out our Western Monarch Call to Action for more information, including what native milkweeds and nectar resources to plant, why it’s important to go pesticide-free in your garden, the importance of overwintering habitat protection, and more.

If you’re a grower in California, check out Xerces’ and the U.S. Fish and Wildlife Service’s A quick guide to monarch habitat on farms in California’s Central Valley, which provides guidance to helping monarchs in a part of the country where they need it the most.

Additional Resources

Learn more about the Xerces Society’s monarch conservation work.

Read about the Xerces Society’s Endangered Species Program.