This croc’s got its eye on you! A new study suggests that crocodiles can sleep with one eye open. Scientists think this behavior helps the reptiles monitor others in their group or watch out for predators, like leopards.

Scientists studying crocodiles in Australia observed that when the animals were resting, they usually closed both eyes. But when another croc or a person was nearby, the animals often closed just one eye. They kept the other eye peeled—and fixed on the person or animal of interest.