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Monarch Butterflies in the Western United States

By Scott Hoffman Black on 20. July 2016
Scott Hoffman Black

Much of the focus on monarch butterflies is on the eastern population. Monarchs in western North America are in greater decline and need conservation help.

The monarch butterfly has received a lot of attention in the last couple of years. Much of that has focused on the population that migrates through eastern North America, as far north as Ontario, and the problems facing the overwintering grounds in Mexico. Monarchs also breed in the western U.S. and research shows that they migrate to both the California coast and Mexican overwintering sites. These western populations are also at risk.

The Xerces Society has been a leader in studying and protecting the western monarchs since the 1980s. We pioneered successful habitat creation in working landscapes and initiated partnerships to produce milkweed seed that can be included in restoration plantings. Thanks to our experience, the Xerces Society is now at the center of many conservation efforts at local, state, national, and international levels. We now have the equivalent of nine full-time staff working on monarch conservation across the U.S.


Monarch butterfly drinks nectar from flowers of narrowleaf milkweed
A monarch nectaring on California narrowleaf milkweed. (Photo: Eric Eldredge / USDA-NRCS)


Research and Protection of Western Monarchs

The Xerces Society is working to better understand the conservation needs of western monarchs through citizen science projects and partnerships with agencies.

  • An analysis in Xerces’ newly released report, State of the Monarch Butterfly Overwintering Sites in California, shows a 74% decline in the California overwintering population since the late 1990s.

  • The data for the report comes from two decades of volunteer monitoring that is organized by the Xerces Society. This effort, called the Western Monarch Thanksgiving Count, locates and counts monarchs overwintering at hundreds of sites along the California coastline each fall.
  • By harnessing the energy of citizen scientists and land managers, Xerces has been partnering with the U.S. Fish and Wildlife Service to compile a database of breeding monarch sightings and milkweed records across the western U.S. As part of this partnership, and partnerships with the U.S. Forest Service and Bureau of Land Management, Xerces staff scientists are surveying public lands in several states for monarchs and milkweeds. The information gained from these efforts is being used to inform models that will help us guide management and restoration for monarchs.
  • Through a partnership with the Idaho Department of Fish and Game and the Washington Department of Fish and Wildlife, Xerces is involving more citizen scientists in gathering data on monarch breeding locations and milkweed occurrence via an interactive website, to be launched this winter.


An overwintering cluster of monarch butterflies in California redwood tree.
With better data to work from, agencies can now prioritize overwintering sites most at risk in California. (Photo: Xerces Society / Carly Voight.)


Improving Monarch Habitat

We have worked to protect milkweed where it exists in the landscape, as well as to promote the production and planting of native milkweeds. We have also worked to promote the use of other plants that have a high nectar value for monarchs.

  • We have worked directly with farmers across the country on habitat restoration efforts that benefit monarchs and other pollinators. This includes tomato farms and almond orchards in California, berry farms in Oregon, and fruit orchards in Washington. To date, the efforts we have supported have culminated in tens of thousands of acres of habitat and many miles of hedgerows.
  • In less than five years, through Project Milkweed, our work with the native seed industry has helped to bring more than 60 million additional milkweed seeds to market in regions such as California and Arizona where native seed had previously been unavailable.
  • We are working with native seed producers to increase the availability and use of nectar plants that are of high value to monarchs, particularly during their fall migration.


Monarch caterpillar feed on woollypod milkweed
Xerces staff scientists are surveying public lands in several states for monarchs and milkweeds. )Photo: Xerces Society / Scott Hoffman Black.)


Working with Landowners and Land Managers

Improving the management of existing monarch habitat is as important as creating new areas.

  • Designed for land managers, Milkweeds and Monarchs in the Western U.S. is a short guide to monarch butterflies’ basic biology and the threats they currently face, and outlines how public and private land managers can become involved with managing, protecting, and enhancing milkweed stands on their land.
  • To better inform and understand the challenges of land managers in the west we are presenting a series of Monarch Conservation and Management Short Courses in 2016 and 2017. These courses are offered to federal, state, local, and tribal land managers in Idaho, Washington, Oregon, California, Nevada, Colorado, and Utah.
  • We are partnering with the states of Idaho Department of Fish and Game and the Washington Department of Fish and Wildlife to integrate monarch butterfly conservation into their respective State Wildlife Action Plans by filling critical data gaps and providing training to state land managers and citizen scientists.
  • We have provided conservation advice and technical information to many state departments of natural resources and transportation, including CalTrans, Washington State Department of Transportation and Colorado Department of Transportation.


Monarch butterflies drink nectar in a field of blazingstar.
We are working with a variety of agencies to preserve, protect, and enhance existing habitat while increasing resource availability to create and expand habitat. (Photo: Minnesota Native Landscapes.)


Protection from Pesticides

Among the causes of monarch decline, insecticide use may be an important yet overlooked factor. Research continues to show the ways in which neonicotinoids, the most widely used group of insecticides in the world, are having devastating effects on pollinator species, and new research reveals that some of these compounds are toxic to monarch caterpillars.

  • To end reliance on toxic pesticides, we provide support to individuals and organizations who want to protect pollinators by limiting the use of pesticides.
  • We are assisting federal agencies in their evaluations of pesticides’ impacts on native species and working with state and tribal governments to develop pollinator protection plans.
  • We are also joining forces with local campaigns seeking to protect their communities from pesticides and with a coalition of nonprofits advocating for pesticide reform nationally.


Monarch caterpillar on leaves of showy milkweed.
Monarch caterpillar feeding on leaf of showy milkweed (Asclepias speciosa). (Photo: Xerces Society / Candace Fallon.)


Working with National and International Agencies

Our work in western states is not done in isolation. Our involvement with national and international bodies advances the science and practice of monarch conservation, and helps to shape the framework for monarch conservation in all regions.

  • We are working with government agencies and monarch scientists in the United States, Mexico, and Canada through our involvement in the Federal Monarch Butterfly High-Level Working Group, the Monarch Joint Venture, and both the National and Tri-National Monarch Conservation Science Partnerships.
  • In April 2016, the Xerces Society was the only non-governmental organization to give a presentation at the XXI Meeting of the Canada/Mexico/U.S. Trilateral Committee for Wildlife and Ecosystem Conservation and Management in Ottawa, Canada.
  • We provide guidance, technical support, and monarch expertise to federal agencies such as the USDA Natural Resources Conservation Service, U.S. Forest Service, U.S. Fish and Wildlife Service, DOI Bureau of Land Management, U.S. Geological Survey, and the U.S. State Department.
  • We are working with North America’s Commission for Environmental Cooperation and the University of Minnesota Monarch Lab to develop a comprehensive guide for private landowners on habitat management best practices, financial incentive programs, and other conservation tools.
  • In collaboration with ICF International, the Xerces Society has developed for the Federal Highway Administration best management practices for roadside maintenance to provide habitat for monarchs and other pollinators.

There is still a long way to go to protect current populations of monarchs and to support their recovery. With strategic partnerships, one of the largest monarch conservation teams in the U.S., and resources to inform an engaged and enthusiastic public, the Xerces Society continues to build on over three decades of work protecting the monarch butterfly. To learn more about all of our monarch conservation efforts, click here to read our July 2016 Monarch Update.


Scott Black is an internationally renowned conservationist who has been at the forefront of the conservation movement for three decades. Scott’s work has led to protection and restoration of habitat on millions of acres of rangelands, forests, and farmland as well as protection for many endangered species. He is an author of the best-selling Attracting Native Pollinators and Gardening for Butterflies and has written more than two hundred other publications including a recent chapter on climate change and insects. Scott serves on the science advisory committee of Nature-Based Climate Solutions, which brings together stakeholders to accelerate the implementation of carbon removal strategies that simultaneously improve the social, economic, and environmental resilience of local communities.

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