Soon after whaling ships began operating in the North Pacific, an interesting trend emerged. Within just a few years, whalers saw a 58% drop in their successful strikes. Sperm whales had suddenly become harder to kill— they had begun fleeing the boats instead of forming their usual defensive circles. Were whales communicating new strategies to each other? David Gruber and Shane Gero investigate. Lesson by David Gruber and Shane Gero, directed by Anna Benner.