Crocodiles Might Literally Sleep With One Eye Open

Have you heard the expression "better sleep with one eye open?" Crocodiles may take that phrase literally, according to a new study. To stay abreast of potential threats in their environment, crocs sometimes keep an eye open while snoozing, scientists found. Lots of animals close only one eye while sleeping, including birds and some aquatic mammals, said John Lesku, a research fellow at La Trobe University in Australia and one of the authors of the new study.