Environmental

Whales have beached throughout human history, with evidence of humans salvaging from stranded sperm whales in southern Spain during the Upper Magdalenian era some 14,000 years before the present.^[2] Some strandings can be attributed to natural and environmental factors, such as rough weather, weakness due to old age or infection, difficulty giving birth,^[9] hunting too close to shore, or navigation errors.

In 2004, scientists at the University of Tasmania linked whale strandings and weather, hypothesizing that when cool Antarctic waters rich in squid and fish flow north, whales follow their prey closer towards land.^[3] In some cases predators (such as killer whales) have been known to panic other whales, herding them towards the shoreline.^[3]

Their echolocation system can have difficulty picking up very gently-sloping coastlines.^[10] This theory accounts for mass beaching hot spots such as Ocean Beach, Tasmania and Geographe Bay, Western Australia where the slope is about half a degree (approximately 8 m [26 ft] deep one km [0.62 mi] out to sea). The University of Western Australia Bioacoustics group proposes that repeated reflections between the surface and ocean bottom in gently sloping shallow water may attenuate sound so much that the echo is inaudible to the whales.^[4] Stirred up sand as well as long-lived microbubbles formed by rain may further exacerbate the effect.

A 2017 study by scientists from Germany's University of Kiel suggests that large geomagnetic disruptions of the Earth's magnetic field, brought on through solar storms, could be another cause for whale beachings.^[5] The authors hypothesize that whales navigate using the Earth's magnetic field by detecting differences in the field's strength to find their way. The solar storms cause anomalies in the field, which may disturb the whales' ability to navigate, sending them into shallow waters where they get trapped.^[5] The study is based on the mass beachings of 29 sperm whales along the coasts of Germany, the Netherlands, the UK and France in 2016.^[5]

"Follow-me" strandings

Some strandings may be caused by larger cetaceans following dolphins and porpoises into shallow coastal waters.^{[citation needed]} The larger animals may habituate to following faster-moving dolphins. If they encounter an adverse combination of tidal flow and seabed topography, the larger species may become trapped.

Sometimes following a dolphin can help lead a whale out of danger: In 2008, a local dolphin was followed out to open water by two pygmy sperm whales that had become lost behind a sandbar at Mahia Beach, New Zealand.^[11]

Orcas' intentional, temporary strandings

Pods of killer whales – predators of dolphins and porpoises – very rarely strand. It might be that killer whales have learned to stay away from shallow waters, and that heading to the shallows offers the smaller animals some protection from predators. However, killer whales in Península Valdés, Argentina, and the Crozet Islands in the Indian Ocean have learned how to operate in shallow waters, particularly in their pursuit of seals. The killer whales regularly demonstrate their competence by chasing seals up shelving gravel beaches, up to the edge of the water. The pursuing whales are occasionally partially thrust out of the sea by a combination of their own impetus and retreating water, and have to wait for the next wave to re-float them and carry them back to sea.^[12]

In Argentina, killer whales are known to hunt on the shore by intentionally beaching themselves and then lunging at nearby seals before riding the next wave safely back into deeper waters. This was first observed in the early 1970s, then hundreds times more since within this pod. This behavior seems to be taught from one generation to the next, evidenced by older individuals nudging juveniles towards the shore, and can sometimes also be a play activity.^[12][13][14]

Sonar

There is evidence that active sonar leads to beaching. On some occasions cetaceans have stranded shortly after military sonar was active in the area, suggesting a link.^[6] Theories describing how sonar may cause whale deaths have also been advanced after necropsies found internal injuries in stranded cetaceans. In contrast, some who strand themselves due to seemingly natural causes are usually healthy prior to beaching:

The low frequency active sonar (LFA sonar) used by the military to detect submarines is the loudest sound ever put into the seas. Yet the U.S. Navy is planning to deploy LFA sonar across 80 percent of the world ocean. At an amplitude of two hundred forty decibels, it is loud enough to kill whales and dolphins and has already caused mass strandings and deaths in areas where U.S. and/or NATO forces have conducted exercises.

— Whitty 2007, p. 50

Others

On June 23, 2015, 337 dead whales were discovered in a remote fjord in Patagonia, southern Chile, the largest stranding of baleen whales to date.^[45] Three hundred and five bodies and 32 skeletons were identified by aerial and satellite photography between the Gulf of Penas and Puerto Natales, near the southern tip of South America. They may have been sei whales.^[46] This is one of only two or three such baleen mass stranding events in the last hundred years. It is highly unusual for baleen whales to strand other than singly, and these Patagonia strandings are tentatively attributed to an unusual cause such as ingestion of poisonous algae.

In November 2018, over 140 whales were witnessed stranded on a remote beach in New Zealand and had to be euthanised because of their declining health condition.^[47] In July 2019, nearly 50 long-finned pilot whales were found stranded on Snaefellsnes Peninsula in Iceland. However, they were already dead when spotted.^[48]

On the evening of November 2, 2020, over 100 short-finned pilot whales were stranded on the Panadura Beach in western coast of Sri Lanka.^[49] Four deaths were reported, and all other whales were rescued.^[50]