were insulated from anthropogenic impacts because of their remote habitat. However, now several issues of concern include: Studies of stranded beaked whales show rising levels of toxic chemicals in their blubber. As a top predator, beaked whales, like raptors, are particularly vulnerable to build-up of biocontaminants. They can ingest plastic (which can be lethal). They more frequently become trapped in trawl nets, due to the expansion of deepwater fisheries. Decompression sickness A major conservation concern for beaked whales (family Ziphiidae) is they appear to be vulnerable to modern sonar operations, which arises from recent strandings that temporally and physically coincide with naval sonar exercises. Mid-frequency active sonar (MFAS), developed in the 1950s for submarine detection, is thought to induce panic when experienced by whales at depth. This raises their heart-rates, forcing them to attempt to rapidly ascend toward the surface in search of air. This artificially-induced rapid ascent can cause decompression. Post mortem examinations of the stranded whales in concurrence with naval exercises have reported the presence of hemorrhaging near the ears or gas and fat emboli, which could have a deleterious impact on beaked whales that is analogous to decompression sickness in humans. Gas and fat emboli have been shown to cause nervous and cardiovascular system dysfunction, respiratory distress, pain, and disorientation in both humans and animals. In the inner ear, gas embolism can cause hemorrhages, leading to disorientation or vestibular dysfunction. Breath-holding divers, like beaked whales, can develop decompression-related problems (the "bends") when they return to the surface after deep dives. This is a possible hypothesis for the mass strandings of pelagic beaked whales associated with sonar-related activities. To illustrate, a diving beaked whale may be surfacing from a deep dive and must pass vertically through varying received sound levels. Since the whale has limited remaining oxygen supplies at the end of a long dive, it probably has limited abilities to display any normal sound avoidance behavior. Instead, the whale must continue to swim toward the surface to replenish its oxygen stores. Avoiding sonar inevitably requires a change in behavior or surfacing pattern. Therefore, sonar in close proximity to groups of beaked whales has the potential to cause hemorrhaging or to disorient the animal, eventually leading to a stranding. Current research reveals two species of beaked whales are most affected by sonar: Cuvier's (Z. cavirostris) and Blainville's (M. densirostris) beaked whales. These animals have been reported as stranding