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. 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. "Follow-me" strandings Some strandings may be caused by larger cetaceans following dolphins and porpoises into shallow coastal waters. 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. It may be possible to train dolphins to lead trapped whales out to sea. 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. 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. 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. Theories describing how sonar may cause whale deaths have also