Pilot whales are among the most social marine mammals, often traveling in pods that include hundreds of individuals. Although these strong social bonds help the whales survive, their herding behavior can also lead to their demise -- as one whale emits a distress call that prompts the other members of the pod to follow. Some scientists believe that the whales become stranded when they are forced to chase prey too close to shore. Predators like killer whales can also cause "panic" within a whale pod, disorienting them and "herding" them towards the shoreline. Other researchers have suggested that the whales' echolocation system may not detect gently sloping coastlines. More controversial theories attribute whale beaching to military sonar and changes in the Earth's magnetic field, which could interfere with the animals' ability to navigate. But none of these theories have yet been proven, and the reason behind mass whale strandings is still a mystery.