Each fall, monarch butterflies across Canada and the United States turn their orange, black and white-mottled wings toward the Rio Grande and migrate over 2,000 miles to the relative warmth of central Mexico.
This journey, repeated instinctively by generations of monarchs, continues even as monarch numbers haveplummeted due to loss of their sole larval food source — milkweed. But amid this sad news, a research team believes they have cracked the secretof the internal, genetically encoded compass that the monarchs use to determine the direction — southwest — they should fly each fall.