Bio-logging technology allows scientists to understand the underwater behavior of marine animals in unprecedented ways. From multi-sensor tags that collect fine-scale data for short durations to satellite-linked tags that collect more coarse data over long time periods, bio-logging tools can be used to better understand the risks that marine animals face from a myriad of anthropogenic sources.  I will use two example studies to illustrate how these different tools are being used to better inform conservation and management needs.  Blue whales in California waters were studied using short-duration motion-sensing and acoustic tags as part of a behavioral response study to understand the impacts of mid-frequency navy sonar.  Humpback whales were studied using a combination of motion-sensing and satellite-linked time-depth recording tags to better understand overlap with the krill fishery in the face of a rapidly changing ecosystem around the Antarctic Peninsula.  These examples highlight how detailed information on the behavior and ecological interactions derived from bio-logging tools and environmental sampling is critical to understand risk, and how we can better conserve and protect these species and their ecosystems.