reported that the extended use of their mid-range sonar likely initiated a sequence of events that culminated in internal bleeding. Autopsies revealed bleeding in the inner ears of three of the beached whales and around the brain of a fourth. It is not known how exposure to sonar resulted in internal bleeding. For the 119 species of marine mammals, as well as for some other aquatic animals, sound is the primary means of sensing the environment and is used for communicating, navigating, and foraging. The ocean environment has always included an abundance of natural noises, such as the sounds generated by rain, waves, earthquakes, and other animals. However, a growing number of ships, oil exploration activities, and military and civilian use of sonar, are adding noise to the ambient sounds
in the oceanic environment.