In March 2025, the monarch butterfly population counts from Mexico were released, showing that monarchs occupied 1.79 hectares in December 2024, up from 0.9 hectares in December 2023. While any increase is good news, this number is still below the average for the past decade, 2.81 hectares, which is itself far less than the area when researchers first started measuring colony size in the early 1990s.
Monarch numbers are driven by factors that affect recruitment (the number of eggs that are laid and that survive to adulthood) and adult survival and successful navigation of the annual cycle of breeding, migrating and overwintering. Recruitment and survival are affected by many factors, including quality of habitat, weather conditions and the presence of lethal agents. Thus, land conversion, climate change, and pesticide usage can all impact monarch numbers. Read more in MBF board member Karen Oberhauser's article here.
Other MBF news covered in this issue include:
- Celebrating anniversaries of overwintering discovery and MBBR - The year 2025 marks the 50th anniversary of the official discovery of the butterfly overwintering colonies, and also the 25th anniversary of the Monarch Butterfly Biosphere Reserve decree, protecting the monarch's winter home. Read about the celebration in Contepec in March here.
- US Fish and Wildlife Service (USFWS) proposes listing monarchs as "threatened" under the Endangered Species Act. The initial public comment period ended but a second comment period was re-opened March 19, closing May 19. Read more about the justification for this proposal and how to add your comments at https://www.fws.gov/initiative/pollinators/save-monarch.
- The Monarch Network (also known as Red Monarca) develops tools to share reports on research carried out in and around the MBBR. The network keeps a website making these reports, announcements of events, and informative videos available in English and Spanish. MBF has funded the Monarch Network for at least ten years. Visit this informative website here.
- Western monarch population drops to near record low - In January, the Xerces Society released the results of the 2024 Western Monarch Count, revealing the second-lowest population since counting began in 1997, with just over 9,000 monarchs recorded. This population count is significantly lower than the counts of the past three years, all of which exceeded 200,000 monarchs. Read details about the western population at xerces.org/press/western-monarch-butterfly-population-declinesto-near-record-low
- Adapting to future climates: Establishing Abies religiosa beyond its upper natural altitudinal limit - Dr. Cuauhtémoc Sáenz-Romero from Universidad Michoacana de San Nicolás de Hidalgo and colleagues continued monitoring and evaluating seedling survival and growth performance of Abies religiosa (oyamel) planted in July 2021 at four altitudes (3400m, 3600m, 3800m and 4000m). Read their update here.
- Another successful year for Alternare - Alternare continued to train and support indigenous communities and ejidos of the MBBR, including new generations of trainers through their Trainer Development Program. Recognizing their significant contributions to communities over the years, Fundación Merced awarded Alternare the prestigious “Razon de Ser” prize in October. Read more about the award and Alternare's work here.
- Beyond the Mexico Book Project - Continuing her important outreach work in the monarch region, environmental educator Ms Estela Romero visited 55 schools, delivering 109 educational books and posters, reaching over 1000 students.
- Reporting from the Monarch Region - Ms Estela Romero also continued her weekly reporting on the overwintering monarchs via the Journey North newsletters.
- 2025 Lincoln Brower Awardees - Two new graduate students are awarded funding from our Lincoln P. Brower Fund.
- Heartfelt Thanks to MBF Champions - MBF is very pleased to welcome Sanctuary of Scentbird, a perfume company championing stewardship of our planet, as our latest MBF Champion. Sanctuary has committed to donating proceeds from sales of their Monarch Butterfly parfum. Thank you Sanctuary and all MBF Champions!
- Spring monarch migration update - Monarchs began to depart from their overwintering sites in Mexico over the last week of February through the first week of March, Estela Romero wrote for Journey North. But before they left, they put on quite a display at El Rosario Sanctuary, with Estela writing that the colony left visitors “frozen and speechless” at the season’s peak. Estela wrote that monarchs had a season of mostly stable conditions except for one late-February hailstorm, which fortunately did not impact the monarchs significantly. Shortly after, most were on their way north. By mid-March, sightings of migrating monarchs began to pick up in Texas, and monarchs were reported in Oklahoma through the end of the month. By end of April, monarch eggs were reported as far north as Iowa. Keep up with migration progress throughout the seasons with Journey North maps
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