Of 78 species of cetacea, only 10 species regularly mass strand and another 10 species occasionally strand. Scientists don't know. Some think that whales strand intentionally to rest or seek safety of land or to rub their skin. Others believe that disorientation, confusion of sonar signals in shallow water, or effects of parasite infestation of the inner ear may cause strandings. However, the most compelling scientific theory about strandings has to do with whales using the earth's magnetic field to navigate their environment.
Many animals can detect the earth's magnetic field.
For example birds use this sense to migrate from North to South during the long seasonal migrations and it is thought that some cetaceans may also use magnetic sensing. This magnetite could be used by whales to sense the magnetic field of the earth. Single strandings occur when one cetacean strands on a beach. Single strandings are most often the result of illness or injury. Sometimes this means that the cetacean died of natural causes and then tides and winds washed them ashore.