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Schultz Research Group Conservation Biology

Conservation of Western Monarchs


The monarch butterfly (Danaus plexippus plexippus) has experienced dramatic declines across North America. In response to a petition to list monarchs under the Endangered Species Act (ESA), USFWS established that a full review to consider monarch protection is warranted. To date, the eastern population of monarchs, which overwinters in Mexico, has been the main focus of research and conservation efforts. However, monarchs west of the Rocky Mountains are also in sharp decline (Pelton et al. 2016). Systematic citizen science monitoring, the Western Monarch Thanksgiving Count, started in 1997 with efforts by the Xerces Society and Mia Monroe. With Elizabeth Crone, Leone Brown, and colleagues at the Xerces Society for Invertebrate Conservation, we are finding that monarchs in the west have declined far more than previously thought (Schultz et al, in press). Our analyses suggest that historic populations of overwintering monarchs were around 10 million butterflies in the 1980s, and that fewer than 300,000 butterflies overwinter in these coastal California groves today.

Part of the challenge for conservation of this iconic species in the West is limited knowledge about their basic biology. Together with Xerces Society, Tufts University and collaborators at WSU Prosser, we have just embarked on a new project working with Department of Defense installations to gain a better understanding of where and when monarch butterflies breed across the west. We are working at sites in California, Oregon, Nevada, Idaho and Washington. The Department of Defense, as a public agency responsible for management of public lands, is extremely interested in efficient and effective conservation strategies which balance training needs with natural resource management. Gaining a greater understanding of monarch biology will help us focus resources and effort in places and times which are most likely to make important contributions to the monarch population. We are currently in the field with this project in 2017 and look forward to gaining a greater understanding on monarch biology as part of this work.

Crone, E.E. and C. B. Schultz. 2021. Resilience or catastrophe? A possible state change for monarch butterflies in the West. Ecology Letters  24:1533-1538

Schultz, C. B. and E. E. Crone 2021. What’s going on with monarchs in the West? A conservation conundrum. News of the Lepidopterists’ Society 63: 34-35

Freedman, M. J., De Roode; M. Forister, M. Kronforst, A. Pierce, C. B. Schultz, O. Taylor, E.E. Crone. 2021 Are Eastern and Western monarch butterflies distinct populations? A review of evidence for ecological, phenotypic, and genetic differentiation and implications for conservation. Conservation Science and Practice 3: e423

Diffendorfer, J. E., W. E. Thogmartin, R. Drum, and C. B. Schultz. 2020. Editorial: North American Monarch Butterfly Ecology and Conservation. Frontiers in Ecology and Evolution 8: Article 576281

Crone, E.E., E. M. Pelton, L. B. Brown, C.C. Thomas, and C. B. Schultz. 2019. Why are monarch butterflies declining in the West? Understanding the importance of multiple correlated drivers. Ecological Applications. e01975

Pelton, E. M., C. B. Schultz, S. J. Jepsen, S. H. Black, E. E. Crone. 2019. Western monarch population plumments: Status, probable causes, and recommended conservation actions. Frontiers in Ecology and Evolution 7:Article 258

Schultz, C. B., L. Brown, E. Pelton, and E. E. Crone. 2017. Citizen science monitoring demonstrates dramatic declines of monarch butterflies in western North America. Biological Conservation. 214: 343-346.

Pelton, E., S. Jepsen, C. B. Schultz, C. Fallon, and S. H. Black. 2016. State of the monarch butterfly overwintering sites in California. 40+vi pp. Portland, OR: The Xerces Society for Invertebrate Conservation. (Available online at