|National Geographic photo|
Insecticides and illegal logging in designated habitats are largely blamed for destroying milkweed plants, which are the main source of food for the butterflies, whose numbers fell 90 percent in recent years after reaching 1 billion in 1996. The U.S. Fish and Wildlife Service in February started a conservation fund for the butterfly and in September announced the first round of grants totaling $3.3 million from the fund.
"The butterflies spend the winter in Mexico and then go through several generations as they fly north, through Oklahoma, on their long migration to Canada," Brandes writes. "While an estimated 1 billion monarchs migrated in 1996, only about 35 million made the trip in 2013, according to Marcus Kronforst, a professor of ecology and evolution at the University of Chicago who has studied monarchs. Their numbers have rebounded in recent years but are still well below what they were two decades ago."