The monarch butterfly populations in North America have experienced declines of nearly 90% in the past two decades. The US Fish and Wildlife Service is considering listing the monarch as a threatened species with the Endangered Species Act.
Three things have been determined to be the major causes of the population decline:
1) decreased winter habitat in Mexico,
2) severe weather due to climate change, and
3) decreased milkweed and habitat in the United States.
Every fall, monarch butterflies travel up to 4000 km from the Great Lakes region in the US and Canada to spend the winter in clusters in the trees of the mountains of central Mexico. A smaller population of monarchs, west of the Rocky Mountains, has a shorter migration to the coast of southern California.
Milkweed (Asclepias) is the host plant for monarch butterflies. Adult butterflies lay their eggs on the underside of milkweed leaves and monarch caterpillars only feed on milkweed plants. Urbanization and use of genetically modified crops has drastically reduced the availability of milkweed. Consider starting your own Monarch Waystation to attract butterflies to your yard!
Report your first monarch butterfly and milkweed sighting at Journey North. This citizen science program allows scientists to collect a large amount of data on the butterflies and their habitat, and allows citizens to participate in conservation. Click the link below to learn about how you can become a citizen scientist!