Western Monarch Thanksgiving Count: Nov. 14 – Dec. 6, 2020

Published on September 22, 2020

Hello Western Monarch Thanksgiving and New Year’s Count Community! Thank you for being a part of this incredibly important community science program! This remarkable volunteer effort collects invaluable data that gives researchers and conservationists a reliable picture of the western …

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2020 International Monarch Monitoring Blitz: July 24 – Aug 2, 2020

Published on July 17, 2020

Join us and thousands of volunteers across North America from July 24 – August 2, 2020 for the 4th annual International Monarch Monitoring Blitz (the Blitz). To participate, simply go out and look for and report milkweed plants and all …

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Monarchs Overwintering in Mexico Down 53%

Published on March 18, 2020

Monarchs still urgently need Endangered Species Act protection in the United States and extraordinary conservation efforts throughout North America. The World Wildlife Fund-Mexico and the Comisión Nacional de Áreas Naturales Protegidas (CONANP) announced today that monarchs in central Mexico occupied …

Monarchs Overwintering in Mexico Down 53% Read More »


New Year’s Count Finds Continued Decline of Monarchs Overwintering in California

Published on March 5, 2020

Monitoring revealed an average decrease of 46% between the Thanksgiving and New Year’s counts. This winter, many waited with bated breath for the results of the Western Monarch Thanksgiving Count (WMTC), which occurs annually around the Thanksgiving holiday. In January, …

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The Vanishing Butterfly Groves of California

Published on January 27, 2020

Action is urgently needed to address the challenges facing monarch butterfly overwintering sites. With the number of western monarchs overwintering in California at less than 1% of historic levels for the second year in a row, it is obvious that …

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Western monarch butterfly population still at critical level

Published on January 23, 2020

PORTLAND, Ore., January 23, 2020—The Xerces Society today announced that the number of monarch butterflies overwintering in California remains at critical levels for the second year. The monarch population during the 2018–19 winter was an all-time low. Unfortunately, this year’s …

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DeWind Alumnae Publish Three New Research Papers about Monarch Butterflies

Published on November 6, 2019

By Candace Fallon and Emma Pelton on 6 November 2019 Together, these publications contribute to our growing understanding of how human actions can hurt—or help—monarchs. Joan Mosenthal DeWind was an early member of the Xerces Society and a keen supporter …

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Western Monarchs: Notes from the Field

Published on November 1, 2019

By Stephanie McKnight and Emma Pelton on 21 October 2019 Updates on a multi-year collaborative research project tracking the imperiled western monarch population. After the sudden and shocking crash in the number of monarchs overwintering in California during the winter …

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Community Science Powers New Western Monarch Studies

Published on July 31, 2019

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 …

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Monarch Conservation Webinar – Western Monarch Population Down by 99%: How You Can Help

Published on February 11, 2019

Location: Online webinar Date & Time: Tuesday, February 26th, 2019 at 2 PM Eastern Time Description: Have you heard about the steep decline in the Western monarch population? Are you wondering how you can help? This webinar will explore the citizen …

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Monarch Butterflies in Western North America in Jeopardy

Published on January 17, 2019

Population of monarchs overwintering in California at lowest level ever recorded Media Contacts: Emma Pelton, Endangered Species Conservation Biologist; [email protected], (971) 533-7245 Sarina Jepsen, Endangered Species Program Director; [email protected], (971) 244-3727 PORTLAND, Ore.; Thursday, 1/17/19—The population of monarch butterflies overwintering in California …

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

Published on

Working at a conservation nonprofit means that we often come across bad news, but the results from this winter’s Western Monarch Thanksgiving Count left us shocked: an all-time record low of 28,429 monarchs at 213 sites. This number is an 86% …

Record Low Number of Overwintering Monarch Butterflies in California – They Need Your Help! Read More »


San Francisco Chronicle article “California’s most famous butterfly nearing death spiral”

Published on January 16, 2019

“An alarming, precipitous drop in the western monarch butterfly population in California this winter could spell doom for the species, a scenario that biologists say could also plunge bug-eating birds and other species into similar death spirals. Only 28,429 of …

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Preliminary Thanksgiving 2018 count results

Published on November 29, 2018

Each year, during a three-week period around Thanksgiving, scores of volunteers fan out through coastal California to find and count overwintering monarch butterflies as part of the Western Monarch Thanksgiving Count. The results are eagerly awaited, as the count provides the …

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Second New Year’s Count Supports Monarchs Movement Between Sites

Published on March 8, 2018

The Xerces Society’s Western Monarch Thanksgiving Count provides a long-running record of the number of monarchs overwintering in California—including the steep decline of recent decades. Volunteers and biologists who take part in the Thanksgiving Count have been invaluable in monitoring …

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Newly released monarch overwintering site management plan provides blueprint for protecting and managing monarch groves

Published on March 2, 2018

The Xerces Society for Invertebrate Conservation, Groundswell Coastal Ecology, California Department of Parks and Recreation, and the U.S. Fish and Wildlife Service have developed a western monarch butterfly overwintering site management plan that also serves as a template for land …

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Western Monarch Butterflies Continue to Decline

Published on February 1, 2018

FOR IMMEDIATE RELEASE Contacts: Sarina Jepsen, Endangered Species Program Director, The Xerces Society for Invertebrate Conservation, (971) 244-3727, [email protected] Emma Pelton, Conservation Biologist, Endangered Species Program, The Xerces Society for Invertebrate Conservation, (503) 232-6639, [email protected] Western Monarch Butterflies Continue to …

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New study shows dramatic decline in the population since the 1980s

Published on September 7, 2017

A new study published today in Biological Conservation shows a dramatic decline in the California overwintering population of monarchs in the past three decades. Press release below: Monarch butterflies disappearing from western North America New study reveals that western monarch …

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First New Year’s Count Completed

Published on June 8, 2017

Volunteers with the Western Monarch Thanksgiving Count have been monitoring the numbers of monarch butterflies overwintering in California every fall for the last twenty years. To better understand overwintering monarch clusters’ persistence during the overwintering season, the Xerces Society and …

First New Year’s Count Completed Read More »


Monterey Herald article “It’s time for the monarch count!”

Published on November 22, 2016

“Pacific Grove >> With deep concentration, they direct their gaze up the trees that play host to slumbering butterflies, silently counting the orange insects until they share their tally with neighboring volunteers. As monarchs flock to the verdant groves along …

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Celebrating 20 years of the Western Monarch Thanksgiving Count!

Published on November 11, 2016

As the days get shorter and monarchs make their way to the forested groves along the California coast to settle in for the winter, volunteers for the Xerces Society Western Monarch Thanksgiving Count are preparing to head out to observe …

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Monarch butterflies and great ways you can help them

Published on November 10, 2016

“Last November, Berkeleyside published an article about a spectacular natural phenomenon seen in Berkeley for the first time: hundreds of monarch butterflies were clustering in the trees of Aquatic Park. This fall, thoughtful reader and independent gardener Toni Cox wrote …

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Russian explorers first to document monarch butterfly in California

Published on October 30, 2016

200 years ago, monarchs were observed along the CA coast – will they be there two centuries from now? Learn more on the Xerces Society Blog.


Monarchs arriving at the Pacific Grove butterfly grove

Published on October 27, 2016

Monarch butterflies are slowly arriving at the Pacific Grove butterfly grove. Nick Stong, who counts monarch butterflies at Pacific Grove every Saturday, is encouraged by the numbers of butterflies that have arrived in the last few weeks. Read more in …

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New report on the State of Overwintering Sites in California

Published on July 8, 2016

A report released today by the Xerces Society shows a sharp two-decade decline in the number of monarchs which overwinter along the California coast and prioritizes the top 50 overwintering sites most in need of conservation and management attention. State …

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Monarch SOS app launched: a new way to collect monarch data

Published on May 5, 2016

A new version of the Monarch SOS app for iPhone is now available through iTunes! This free app developed by Naturedigger includes many monarch citizen science projects and the newest version adds two Xerces projects: Western Monarch Count– for monitoring …

Monarch SOS app launched: a new way to collect monarch data Read More »


Monarch Numbers Up in Mexico, But Still a Long Journey to Recovery

Published on February 26, 2016

Favorable weather boosts Mexican overwintering population but numbers remain relatively low. PORTLAND, Ore., February 26, 2016 — The latest count of monarch butterflies overwintering in Mexico found that the population which will migrate to the United States rebounded again this …

Monarch Numbers Up in Mexico, But Still a Long Journey to Recovery Read More »


Assessment of Western Monarch Butterfly Winter Population Completed

Published on February 4, 2016

The Xerces Society for Invertebrate Conservation, Portland, OR More monarchs reported in Northern California this year, but monarchs are not yet recovered PORTLAND, Ore., February 4, 2016 — Results from a survey of monarch butterfly overwintering sites in California show …

Assessment of Western Monarch Butterfly Winter Population Completed Read More »


New study on the natal origins of overwintering monarchs

Published on January 26, 2016

A new study by UC-Davis illuminates the natal origins of monarch butterflies overwintering in California. The study by Louie Yang (Dept. Entomology at UC-Davis) used stable hydrogen isotope analysis to test tissue samples from 114 butterflies at 4 overwintering locations. The …

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New data suggests 2015 a good year for monarch butterflies

Published on December 18, 2015

New data suggests the number of monarch butterflies in California has grown this year. That’s good news since the population of this near-threatened species has been thin in recent years. “We are really pleased to see that the number of …

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Monarch count: Pacific Grove numbers down this year

Published on

The monarch butterflies have returned to Pacific Grove, but this year there may be fewer of them. Volunteers and officials with the Pacific Grove Museum of Natural History recently counted 11,000, down from 18,000 this time last year. That count …

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Monarch Butterflies of Ellwood Mesa

Published on

Monarch butterflies travel hundreds of miles each fall to bask in the warmth of secluded eucalyptus, Monterey pine and coast live oak groves along the central California coast. They cluster in the hundreds and even thousands, appearing as a mass …

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Early data from Western Monarch Thanksgiving Count suggests a small increase in butterfly numbers in some parts of the overwintering range

Published on December 14, 2015

Populations of monarch butterflies are still far below historic numbers PORTLAND, Ore., December 14, 2015 — First reports from monarch overwintering sites in California surveyed during the Xerces Society’s Western Monarch Thanksgiving Count suggest that 2015 may have been a …

Early data from Western Monarch Thanksgiving Count suggests a small increase in butterfly numbers in some parts of the overwintering range Read More »


Migrating monarchs bring out citizen scientists in the holiday season

Published on December 5, 2015

Every autumn, the western North American population of monarch butterflies migrates from the lands west of the Rocky Mountains to the coast of California, where they spend the winter at about 200 sites scattered throughout the coastline. Last winter, I …

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Hundreds of monarch butterflies cluster in Berkeley’s Aquatic Park

Published on November 23, 2015

In late October, Berkeleyside received a tip that thousands of tiny fish were jumping in the waters of Aquatic Park. Less than three weeks later, we received another “scoop” about the park that throngs of monarch butterflies were clustering in …

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Monarch Welcoming Committee

Published on November 17, 2015

“These butterflies migrate thousands of miles, but the more amazing part is that even with four or five generations between them, they still return to these same branches,” explained Charis Van der Heide, who is a docent at the Coronado …

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