Light Pollution Can Disorient Monarch Butterflies

Biologists say night-time light pollution can interfere with the remarkable navigational abilities of monarchs, which travel as far as Canada to Mexico and back during their multi-generational migration. Researchers found that butterflies roosting at night near artificial illumination such as a porch or streetlight can become disoriented the next day because the light interferes with their circadian rhythms. Artificial light can impede the molecular processes responsible for the butterfly's remarkable navigational ability and trigger the butterfly to take wing when it should be resting. Even a single light can throw off the butterfly's internal compass. Besides planting milkweed in the garden, people interested in helping monarch butterflies might want to turn off the porch light.

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Biologists at the University of Cincinnati say night-time light pollution can interfere with the remarkable navigational abilities of monarchs, which travel as far as Canada to Mexico and back during their multigenerational migration. Researchers found that butterflies roosting at night near artificial illumination such as a porch or streetlight can become disoriented the next day because the light interferes with their circadian rhythms. Artificial light can impede the molecular processes responsible for the butterfly's remarkable navigational ability and trigger the butterfly to take wing when it should be resting.

“We found that even with a single work light that you find at a construction site, monarch butterflies treat that like it’s the sun,” UC assistant professor Patrick Guerra said.

The study was published in the journal iScience.