Nonmigratory monarch butterflies in Central and South America were not designated as endangered. “There are things people can do to help,” she said, including planting milkweed, a plant that the caterpillars depend upon. This population has seen an even more precipitous decline than the eastern monarchs, although there was a small bounce back last winter.Įmma Pelton of the nonprofit Xerces Society, which monitors the western butterflies, said the butterflies are imperiled by loss of habitat and increased use of herbicides and pesticides for agriculture, as well as climate change. “It’s a true spectacle and incites such awe,” said Anna Walker, a conservation biologist at New Mexico BioPark Society, who was involved in determining the new listing.Ī smaller group spends winters in coastal California, then disperses in spring and summer across several states west of the Rocky Mountains. The offspring that reach southern Canada then begin the trip back to Mexico at the end of summer. In North America, millions of monarch butterflies undertake the longest migration of any insect species known to science.Īfter wintering in the mountains of central Mexico, the butterflies migrate to the north, breeding multiple generations along the way for thousands of miles. Haddad, who was not directly involved in the listing, estimates that the population of monarch butterflies he studies in the eastern United States has declined between 85% and 95% since the 1990s. “It’s very easy to imagine how very quickly this butterfly could become even more imperiled.” “What we’re worried about is the rate of decline,” said Nick Haddad, a conservation biologist at Michigan State University. The group estimates that the population of monarch butterflies in North America has declined between 22% and 72% over 10 years, depending on the measurement method.

The International Union for the Conservation of Nature added the migrating monarch butterfly for the first time to its “red list” of threatened species and categorized it as “endangered” - two steps from extinct.

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