been advanced after necropsies found internal injuries in stranded cetaceans. In contrast, some who strand themselves due to seemingly natural causes are usually healthy prior to beaching: Direct injury The large and rapid pressure changes made by loud sonar can cause hemorrhaging. Evidence emerged after 17 cetaceans were hauled out in the Bahamas in March 2000 following a United States Navy sonar exercise. The Navy accepted blame agreeing that the dead whales experienced acoustically induced hemorrhages around the ears. The resulting disorientation probably led to the stranding. Ken Balcomb, a cetologist, specializes in the killer whale populations that inhabit the Strait of Juan de Fuca between Washington and Vancouver Island. He investigated these beachings and argues that the powerful sonar pulses resonated with airspaces in the dolphins, tearing tissue around the ears and brain. Apparently not all species are affected by sonar. Injury at a vulnerable moment Another means by which sonar could be hurting cetaceans is a form of decompression sickness. This was first raised by necrological examinations of 14 beaked whales stranded in the Canary Islands. The stranding happened on 24 September 2002, close to the operating area of Neo Tapon (an international naval exercise) about four hours after the activation of mid-frequency sonar. The team of scientists found acute tissue damage from gas-bubble lesions, which are indicative of decompression sickness. The precise mechanism of how sonar causes bubble formation is not known. It could be due to cetaceans panicking and surfacing too rapidly in an attempt to escape the sonar pulses. There is also a theoretical basis by which sonar vibrations can cause supersaturated gas to nucleate, forming bubbles, which are responsible for decompression sickness. Diving patterns of Cuvier's beaked whales The overwhelming majority of the cetaceans involved in sonar-associated beachings are Cuvier's beaked whales (Ziphius cavirostrus). Individuals of this species strand frequently, but mass strandings are rare. Cuvier's beaked whales (Ziphius cavirostrus) are an open-ocean species that rarely approach the shore, making them difficult to study in the wild. Prior to the interest raised by the sonar controversy, most of the information about them came from stranded animals. The first to publish research linking beachings with naval activity were Simmonds and Lopez-Jurado in 1991. They noted that over the past decade there had been a number of mass strandings of beaked whales in the Canary Islands, and each time the Spanish Navy was conducting exercises. Conversely,