The news came as no surprise to Karen Oberhauser, director of the University of Wisconsin-Madison Arboretum. A globally recognized expert on monarch butterflies, Oberhauser has been studying the species for nearly 40 years.
When she first began studying monarchs in 1985, butterflies of the migratory subspecies were plentiful. But over the last 10 years alone, the eastern migratory monarch population has declined between 22% to 72%, according to the IUCN. The western population, which spends the winter in California, has declined between 66% to 91%.
