by Karen Oberhauser, Wisconsin Monarch Collaborative
A month ago, the leading edge of the migration had moved well into Mexico, and I noted that the very first monarchs should begin arriving at their winter homes right on time, around the Day of the Dead celebration on November 2, with larger numbers a week or so behind. Just like clockwork, this is what happened. Estela Romero sent a report to Journey North of monarchs in the skies above the small town of Angangueo Michocan on November 4. The sanctuaries of El Rosario and Sierra Chincua in the Monarch Butterfly Biosphere Reserve officially opened to the public on November 22.
Late Season Monarchs in Wisconsin
The last monarch reported to WisconsinButterflies this year was on November 5, in Milwaukee County. But this butterfly had just emerged and had deformed wings; the last monarch in good condition was reported by observer Lindsey Dalton at Olbrich Botanical Gardens in Madison on November 4.
Figure 1 (above). Journey North map of fall roost sites downloaded 22 November 2025. For up-to-date details, click here.
Figure 2 (left). Final Wisconsin report of a healthy monarch to wisconsinbutterflies.org, just as the first monarchs were arriving at their winter home in Mexico. Hopefully she found more nectar sources as she flew south!
New Method for Tracking Migrating Monarchs
The biggest news in Monarch Science this fall is the deployment of BlūMorpho transmitters on migratory monarch butterflies. Just over 400 monarchs were outfitted with tiny transmitters in spots throughout their migratory range and tracked through amazing new technology. This technology allows smartphones and other Bluetooth enabled devices to track the tagged butterflies and resulted in our first-ever real-time pictures of monarch migration routes.
You can join Project Monarch by downloading the free app. For more details, check out the project website or read the NYT article about it.
Figure 3. Tracks of tagged monarchs in Autumn 2025, copied from Project Monarch website.
Figure 4. Track of a single tagged monarch (screenshot from app). Each dot represents a “capture” by a blue-tooth enabled device; this monarch was “captured” 1357 times
If you’d like to help monarchs, one of the best things you can do is provide habitat for them. Check out the Wisconsin Monarch Collaborative website for great advice on how to do this. The Monarch Joint Venture has a free webinar series with exciting speakers every month, on topics ranging from fascinating biology to practical conservation tips.
