The dolphins could jump the nets. In the cove at Taiji, Japan, hunters drive them into shallow water, and they huddle together and stay.

Lori Marino, a neuroscientist who studies dolphin brains, told the writer Susan Casey she can’t explain it. Pods do something similar on beaches, where whole groups strand when only one or two animals are sick. Marino calls it “some sort of cohesiveness” that humans still don’t grasp.

Casey wondered if it began when dolphins grew smaller and their teeth less frightening. Weaker alone, they would need each other. Marino agreed, and she suspects that kind of social life may be why their brains grew so big. A dolphin keeps track of close allies and the allies of those allies. Most of us struggle to keep up with one group chat.