‘Canary in the cornfield’: monarch butterfly may get threatened species status

By Morgan Erickson-Davis, mongabay.com

Monarch butterflies were once a common sight throughout the North American heartland. In Mexico, where they overwinter, single trees would often be covered in thousands. But declines in milkweed – their caterpillars’ only source of food – have led to a 90 percent decline in monarch numbers. Now, the U.S. Fish and Wildlife Service (USFWS) is reviewing a petition that would grant the iconic species protection through the Endangered Species Act (ESA).

The monarch (Danaus plexippus) is one of the world’s greatest insect migrators, flying 3,000 miles (4,800 kilometers) over four generations from breeding grounds as far north as Nova Scotia to forests in Mexico where they overwinter. However, fewer and fewer have been congregating in Mexico. Surveys conducted by scientists have tracked an overall steep decline over the past two decades.

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