Dr. Nachtigall is interested in the sensory systems of marine mammals and started with vision in clawless otters. Lately he has focused on hearing and echolocation in cetaceans. He has worked closely with collaborators to develop a reasonable way to measure hearing in cetaceans and polar bears measuring brain wave patterns and amplitudes in response to sounds. This technique has also allowed researchers to measure hearing while animals echolocate and it has been found that they can avoid loud sound by internally ‘plugging their ears’ when necessary or by making hearing more sensitive when listening for faint echoes.