Exclusive updates about the state of monarchs written by Dr. Karen Oberhauser
Wisconsin provides critical breeding habitat for monarch butterflies, and there are many individuals, organizations, agencies, and businesses working hard to ensure monarchs thrive here. Is it working?
These monthly updates are provided by Dr. Karen Oberhauser, one of the world’s leading experts on monarch butterflies, a member of the Wisconsin Monarch Collaborative, and a Wisconsinite! These exclusive updates provide you with the latest science-based information about monarch populations that you won’t find anywhere else.
Thank you to Dr. Oberhauser for providing these updates!
Fall is a great time to add Safe for Monarchs plants to your yard. Fall plants benefit from warmer soil temperatures, typically more rain, and less heat stress. For gardeners, it means less watering and plants that are already in the ground during the busy spring season.
The second half of August is a particularly interesting time to observe monarchs in their northern breeding range. Beginning on about August 15, monarchs emerge from their pupae in diapause. Responding to cues that include both daylength and sun angle, these adults do not become reproductive soon after emerging.
Photo by Tom Koerner/USFWS
The first monarch generation of 2026 began as eggs in the southern US, the offspring of monarchs that had overwintered in Mexico. These first-generation monarchs continued the journey northward, arriving in Wisconsin in late April and May, laying eggs as they moved north.
Photo by Laura Perlick / USFWS
Monarchs from the generation that emerged last autumn began heading north from Mexico in March, laying eggs along the way. By now, that generation has died, and their offspring are continuing the journey northward. Based on counts from CONANP and the World Wildlife Fund-Mexico, about 64% more monarchs headed northward in spring 2026 than in 2025.
Photo by TexasEagle
From early November until mid-March, most Eastern North American Migratory monarchs were in Central Mexico, waiting to head back north to produce what will become the first new generation of 2026. Estela Romero of Journey North reported early departures in late February, and final massive departures on March 7 and 8. These monarchs, most of whom began their lives as eggs in monarchs’ northern breeding grounds last August and September, are now heading north, laying eggs along the way.
Photo by Brenna Weisner
Since early November last fall, most monarchs in the Eastern North American Migratory Population have been overwintering in Central Mexico, waiting for the environmental cues that will signal that it’s time to move back north. Even before the monarchs leave, mating will begin, and they’ll continue to mate and the females will lay eggs as they head north, through northern Mexico and into Texas before spreading into approximately the southeastern quarter of the U.S. This should begin in a little under a month.
Photo by Karen Oberhauser
