Dolphin "Chat Line" to Help Deaf Mom's Calf "Talk"

Sara Bennington
for National Geographic News
April 25, 2007

An underwater "chat line" may help stimulate communication development in an unborn dolphin—in ways the calf's mother, which is deaf, cannot.

Castaway, a pregnant Atlantic bottlenose dolphin, has been living at the Marine Mammal Conservancy (MMC) in Key Largo, Florida, since January, when she was found stranded in Vero Beach.

A battery of tests determined that the mother-to-be is profoundly deaf. Deafness can be fatal for dolphins in the wild. The animals rely on echolocation—the sending and receiving of sound waves—to socialize, find prey, and avoid predators.

"Dolphins live in a world of sound," said MMC president Robert Lingenfelser. "The inability to hear makes them blind, in a sense." (Related: Bottlenose dolphin facts, audio, video.)

Scientists do not know what caused Castaway's deafness, but they doubt that the dolphin has been deaf since birth.

The bottlenose is about 27 years old. Researchers believe it is highly unlikely that she would have survived so long in the wild, even with help from her pod, if the dolphin had been deaf its entire life.

Concerns for Calf

Castaway's deafness could also hinder her ability to teach her calf vital developmental skills.

The first few months of life are the most critical for newborn dolphins to learn survival skills, Lingenfelser says.

To date, Castaway has only uttered a few sounds in a low-frequency monotone—a stark contrast to an average dolphin's steady stream of high-frequency chirps, squeaks, and clicks.

"Probably our biggest concern is that the calf will not develop the ability to communicate if the mother is not communicating," said Jill Borger-Richardson, director of research and education at Dolphins Plus, a Key Largo dolphin and marine mammal research and education facility.

Dolphins Plus scientists have consequently recorded several "conversations" of their hearing dolphins. Those recordings are now being played in Castaway's pen via underwater speakers to promote the fetal calf's communication development.

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