Whales and dolphins beach themselves, or end up beached, for reasons ranging from injury and illness to polluted water and simply becoming stranded at low tide. When these creatures travel in pods, the entire pod is likely to end up beached if the leader accidentally strands itself on shore, explains Mental Floss.
When whales and dolphins are injured by boats or other sea creatures, they are often too weak to stay afloat. Mental Floss reports that a number of mass beachings occurred only a short time after the use of sonar during U.S. Navy exercises. There is evidence to suggest sonar confuses whales and dolphins as they attempt to navigate waters.
Whale Facts reports that marine mammals often beach themselves in an effort to avoid sharks or orcas, also known as killer whales. Some biologists are convinced that changes in the Earth's magnetic field interfere with whales' and dolphins' ability to navigate, causing them to end up stranded on shore. Still other scientists suspect global warming, the melting of icebergs and the resulting change in the location of ocean food sources are leading some whales and dolphins to hunt for food closer to shore, where they are more likely to become stranded.