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Where are the Monarchs?

Jul 18, 2016


  • Population Trends

Article originally published on the University of Minnesota Monarch Lab blog.

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.

The storm caused immense destruction, but it was hard to tell how this would impact the monarchs and their habitat. However, the storm clarified the importance of a large, robust monarch population. If it had hit two years ago, when the monarch population was at its lowest level ever (under one hectare), it is not clear that the population could have recovered. See the recent Monarch Conservation Science Broadcast of the MJV/NCTC webinar series for a discussion of the importance of a robust population. If we can say that anything is “lucky” about such a destructive event, we are lucky that the population did so well in summer 2015.

Right after the storm, monarchs were spotted traveling north. Journey North received their first reports on March 14th, and while the numbers spotted by citizen scientists during the spring migration were low, monarchs did move into their northern breeding grounds, and by June 16th, the migration was approaching its northern extent. For maps of the migration this year visit Journey North’s website.

Monarch Larva Monitoring Project data confirm the low numbers reported by Journey North volunteers. We are seeing numbers that rival those of 2013, which resulted in the lowest number of monarchs ever seen in Mexico. However, we know that the population did rebound from the low numbers a few years ago, and that, with our help, they can do it again. And the population is still building this summer. Monarchs are around, just not in the numbers that we’ve seen in the past; we’re starting to hear more positive reports from people throughout the breeding range who have seen their first monarch adults, eggs, or larvae of the year.  

So let’s continue to do what we can. Create habitat for monarchs so the females don’t need to fly long distances between milkweed patches. Join a citizen science project to help us document the state of the population. And, please consider supporting the Monarch Joint Venture, or other organizations working to preserve space for the creatures with which we share this earth.  

The Monarch Joint Venture is a national partnership of federal and state agencies, non-governmental organizations, and academic programs working together to conserve the monarch butterfly migration. The content in this article does not necessarily reflect the positions of all Monarch Joint Venture partners. Header photo by Wendy Caldwell.