University of Minnesota


Category: Monarch Population Trends

Where Are All The Monarchs?

On March 9th 2016, just days after we’d heard the good news that monarch numbers had rebounded to cover just over 4 hectares of forest in the mountains of central Mexico; a huge winter storm hit their wintering sites and the surrounding area. The storm began with rain and was followed by hail, snow, and sub-freezing temperatures. The freezing temperatures killed many monarchs and the strong winds caused trees to topple over, losing monarch habitat. Because the spring migration from Mexico just started, the full population was in the storm's path. Read More »

2015 Population Update and Estimating the Number of Overwintering Monarchs in Mexico

Yesterday evening the eastern monarch butterfly population numbers were released to the public. The colonies measured an area of 1.13 hectares this year, up 69% from the record low population last year but still one of the lowest populations ever recorded. The monitoring, which was conducted by the National Commission of Natural Protected Areas (CONANP) in coordination with the WWF-Telcel Alliance, revealed that there were 9 different colonies. The El Rosario Sanctuary in Michoacán contains 50.4% of the total population this winter. The press release is available in Spanish here. Read More »

2010 MLMP updates from Karen Oberhauser

Dear MLMP Monitors: There’s no milkweed up in central Minnesota yet, but it’s good to read reports of monarchs moving north from southern MLMP team members. I’m sending a few quick reminders about the upcoming monitoring season, our new website, and exciting data analyses. Since we’ve made a few changes to our data sheets, please download them from the website to make sure you’re using the most current versions. As always, please let us know if you have questions or comments, and THANKS for your great work. Read More »

2008 Status of Population: Loss of Winter Habitat

Every fall, monarch butterflies return from their summer breeding grounds in the Eastern US and Canada to 12 forested mountaintops in central Mexico. Millions of monarchs arrive on these mountaintops in early November, clustering on the branches and trunks of trees, waiting for spring when they return north. Most of the sites on which monarchs survive over the course of the winter are protected by a decree of the Mexican government which created the Monarch Butterfly Biosphere Reserve. Despite the protection of this Reserve illegal logging still occurs, resulting in the loss of critical monarch habitat. Read More »

2005 Monarch Population Update

Unfortunately, the news this year on the status of the monarch population is not good. We hope that monarchs rebound from their all-time low numbers right now, and encourage everyone to spread the news of the importance of preserving suitable habitat for monarch butterflies. Read More »

Monarch Population Numbers: March 2002-March 2003

Our 2002 newsletter provided an update on the effects of a winter storm that killed millions of overwintering monarchs in January 2002 (see archived newsletter at Samples of dead butterflies collected after this storm led to estimates that up to 80% of the population died in the storm’s aftermath, and the Eastern migratory population may have been smaller than at any time since scientists began estimating monarch numbers. Read More »

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