'Voices in the Ocean': The whip-smart dolphin brain

'Voices in the Ocean' by Susan Casey
'Voices in the Ocean' by Susan Casey
Courtesy of Penguin

Researchers have long known that dolphins are exceptional mammals, and the list of what they are capable of continues to grow.

According to Susan Casey's book, "Voices in the Ocean," dolphins can count, grieve, deduce, seduce, form cliques, throw tantrums and even call themselves by name. (In this case, their "name" is a whistle — each dolphin is assigned a distinct whistle sound at birth.)

Casey joined MPR News' Kerri Miller to discuss the wild world of dolphins, and the dangers they face in the ocean.

In researching her book, Casey spent two years traveling the globe, researching dolphins and their connection to humanity. Humans and dolphins share a focus on social groups — and a similar brain structure.

The evolution of the dolphin's brain is a fascinating one. Fifty-five million years ago, dolphins' ancestors looked like small-hooved wolves that roamed the land.

Gradually, they moved to the water, and by 35 million years ago, dolphins had developed the ability to live under water full-time. Their brains grew rapidly as their bodies slimmed down.

Today, researchers continue to probe the extent of dolphins' intelligence. Dolphins were the first non-primates to pass the "mirror self-recognition test" — recognizing their own reflection. Since then, elephants and magpies have also passed the test.

Despite their intelligence, dolphins face numerous pressing threats, which Casey covers in "Voices." From the harmful impact of military sonar to the annual hunting rituals in Japan, the dangers to dolphins are numerous and global.

In some cases, it's humans' fascination with dolphins that is the threat. Numerous dolphins are caught and sold into captivity each year so that people can experience them at resorts or other attractions.

Out of their natural habitat, Casey said, it's not an authentic view. "You might as well be looking at an animatronic toy," she said. "Because all the things that make a dolphin a dolphin are missing."