brown tree snake (IMAGE) Colorado State University Caption The brown tree snake, which is nocturnal, was accidentally introduced to Guam in the late 1940s or early 1950s. Credit Bjorn Lardner, United States Geological Survey Usage Restrictions None License Licensed 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.