The Eurasian otter is a secret resident at Germany’s waterbodies. Even in places where otters are common, one must be lucky to see an otter in the wild. As they are nocturnal and quickly move between places, even scientific methods are not sufficient to answer all questions about how otters live. So far, otters have kept many secrets to themselves. Here, up-to-date information available on Eurasian otters is presented.