My research focuses on behavioral and physiological ecology of marine mammals; sensory systems involved in under-ice navigation by seals; and psychophysical studies of captive marine mammals. Over the years my students and I have developed acoustic tracking systems for studying seals, and radio and satellite tracking systems for studying whales. For the past decade or more I have been involved in the issue of ocean noise and marine mammals. I have served on and chaired National Academy of Sciences committees addressing these topics.