Monarchs (IMAGE) University of Cincinnati Caption Monarch butterflies often roost together at night when the temperature drops during their migration. University of Cincinnati biologists found that even a single bright light by these roosts can throw off their daytime navigation. Credit Michael Miller Usage Restrictions None License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.