Migration Milestones

Karen Oberhauser discusses the new data on monarch winter population numbers. Along the East Coast, monarchs are making northern progress and entering new states and provinces. And Western monarchs are venturing beyond California to Nevada, Utah, and Oregon.

Monarch on purple milkweed in Connecticut

Message from Karen Oberhauser: Monarch Winter 2021–2022 Population Numbers Released

Karen Oberhauser, Director of the University of Wisconsin Madison–Arboretum, provides context for understanding the recent release of monarch winter population numbers. Karen writes, "It is likely that monarch numbers would be even lower without the efforts of dedicated individuals throughout North America, but current numbers show us that we need to increase our efforts. Each one of us needs to do what we can to mitigate climate change and provide habitat for monarchs and the hundreds of species that share their habitats."

Eastern Monarch Population

Eastern Monarch Spring 2022 Report #9

The leading edge of migration is still scattered between latitude 42-46°N. Activity remains high in the Upper Midwest and is picking up in Southern Ontario. Northern progress accelerated the most along the East Coast where monarchs are now venturing into New Hampshire, Maine, New Brunswick, and Nova Scotia. And milkweed is emerging near the northern limit of its range throughout Canada.

Western Monarch Population

Letter from Gail Morris: Western Monarch Spring 2022 Report #9

In the Western U.S., monarchs are expanding their range as they head to their summer breeding grounds. Gail Morris writes, "This week monarchs passed a major milestone, crossing over the Sierras, and were spotted in Gardnerville, Nevada, for the first time. And a new sighting in Oregon appeared as well. At the same time monarchs are still being reported in the desert in Las Vegas. Meanwhile monarch adults and immatures flourish in California and continue to grow in number in Utah as monarchs expand their range moving northward. By middle June their flight will stall as they set up their summer breeding grounds."