Ask A Marine Biologist: Why Do Whales Strand?

In the wake of the recent beachings of pods of pilot whales in Snæfellsnes and Reykjanes, we reached out to marine biologist Edda Elísabet Magnúsdóttir, to ask: why do whales strand?

Pilot whales come into shallow waters for many reasons. Sometimes they are avoiding or escaping something, such as sound pollution from sonar or seismic activity. But there is also another reason, which is probably the most likely one: They are following prey.

Pilot whales primarily feed on squid. But, in some cases, when that prey is scarce or that prey moves, the whales swim to other types of prey. We think they are currently hunting mackerel. Mackerel fishermen see them around their boats, they are seen where there is a lot of mackerel, and we know that the whales sometimes feed on them.

The whales also go into shallow waters because there are forces they are not specifically adapted to, such as strong tidal currents. Strandings have been happening during spring tide—which actually occurs in mid-late summer—when there is a large difference between low and high tide. The tide will go out rather quickly and they’re suddenly stranded.

What could also be happening is the leading animal, usually a matriarch, might somehow be disoriented, lost, sick, or hurt, so she might not be able to navigate properly, and the group follows. Pilot whales have strong familial bonds, and they don’t leave each other, particularly not the matriarch. So if she gets into trouble, the whole pod gets into trouble.