Conservation Status and Ecology of the Monarch Butterfly in the United States
NatureServe and the Xerces Society used NatureServe’s conservation status assessment methodology to determine the level of imperilment of the monarch. The methodology has been successfully applied to hundreds of species of animals. Using data on population abundance, trends, and threats, the team of scientists determined that while the monarch butterfly species as a whole, Danaus plexippus, is apparently secure, the subspecies occurring in North America, Danaus plexippus plexippus, is vulnerable to extinction. Under the assessment, the North American monarchs were split into an eastern population that migrates from as far north as southern Canada to central Mexico each fall, and a smaller western population, that largely migrates to coastal California to spend the winter. The eastern monarch population was assessed as “critically imperiled” due to recent rapid decline and widespread threats. The western population, with a slightly slower rate of decline and less widespread threats, was categorized as “vulnerable to imperiled.”
The assessment was done as part of a report prepared for the U.S. Forest Service. The report, Conservation Status and Ecology of the Monarch Butterfly in the United States, summarizes the monarch’s North American distribution, life history, population, current conservation status, and potential causes of decline. In addition, the authors include a set of breeding and overwintering habitat management recommendations.