DON'T LEAVE THE LIGHT ON

A recent study found that nighttime artificial light may interfere with fall monarch migration

BESIDES PLANTING MILKWEED in their gardens, people interested in helping monarch butterflies might want to turn off the porch light.

Biologists at the University of Cincinnati say nighttime 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 navigational mechanisms 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.

Watching their erratic, circuitous movements taking them to and fro across your garden, you might find it hard to imagine monarch butterflies sticking to a rigid flight plan. But their migrations take some monarch populations thousands of miles the same forests in Mexico where they spend the winter.