In one of my classes today, someone mentioned a video they recently saw in which a pod of dolphins stranded themselves on the beach. She went on to talk about how several people on the beach immediately leapt into action and attempted to return them to their ocean home. Interested, I watched the video and was extremely impressed by the immediate response of the onlookers.
After watching, I started to think about why dolphins strand themselves, so I decided to look into it. Apparently, group strandings like the one in the video are not extremely uncommon. However, researchers still do not know why they do it. When 30 dolphins beached themselves in Brazil last year, proposed ideas included that the head dolphin was sick and beached itself, while the others followed; or that the dolphins were following a school of fish and didn't realize how close they were to the shore. However, this idea did not seem to be a possibility in 2008, when several pods beached themselves along the Cornish coast. At the time of the article, none of the post-mortems of the animals showed an illness, implying that the blame fell onto sonar. Yet another incidence of mass strandings, this time all over the world in 2012, caused researchers to believe that the weather was the primary cause of the unusual cetacean behavior.
My conclusion from this search is that humans really have no clue why dolphins strand themselves in groups. An interesting research area for one of us CCS Biology students perhaps?